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ICQF-17 / 1
3rd International Conference
Quantum Foundations 2017
(ICQF-17)
04-09 December, 2017
Program and Book of Abstracts
Venue: Hotel Panache, Patna
Organised by
Department of Physics
National Institute of Technology Patna
India
ICQF-17 / 2
ICQF-17 / 3
PROGRAM
4th
December 2017
Event Timing (IST)
REGISTRATION 09:00 - 10:00
INAUGURATION 10:00 - 10:30
TEA BREAK 10:30 -11:00
Name of the
speaker
Title of the talk Timing (IST) Duration**
(minutes)
Chair: G. S. AGARWAL
P. Busch* Quantum Uncertainty Regions – Theory and
Experiment
11:00 - 11:45 45
D. Home* Generalised Weak Measurement assisted Remote
State Preparation and Demonstration of Hidden
Nonlocality
11:45 - 12:30 45
M. Pawlowski Random access codes - a review 12:30 - 13:05 35
Lunch (13:05 - 14:30) #
Chair: P. GHOSE
S. M. Roy* Contractive Quantum States 14:30 - 15:15 45
C. Branciard Multipartite quantum processes and correlations
with no definite causal order
15:15 - 15:50 35
Y. C. Liang What can we learn from the apparent violation
of the nonsignaling conditions?
15:50 - 16:25 35
Tea break (16:25 - 16:50)
Chair: D. HOME
A. R. Usha Devi Asymptotic limit of diffusive quantum
trajectories
16:50 - 17:25 35
H. F. Hofmann Superpositions of causality: an analysis of the
mechanisms of control in the quantum limit
17:25 - 18:00 35
Dinner (19:00 - 21:00) ##
5th
December 2017
Chair: P. BUSCH
G. S. Agarwal* Subradiance to Hyperradiance in Strong
Coupling Cavity QED
9:30 - 10:30 60
P. Ghosh Quantum and Classical Mechanics: Building A
Bridge
10:30-11:05 35
P. K. Panigrahi Quantum coherence, Holevo Bound and
Quantum Discord
11:05 – 11:40 35
Tea Break (11:40 - 12:00)
Chair: A. R. USHA DEVI
Y. Shikano Quantum Phase through Quantum Tunneling 12:00 - 12:35 35
S. Banerjee Aspects of Non-Markovianity In Quantum
Walks
12:35 - 13:10 35
Lunch (13:10 - 14:20) Chair: L. MACCONE
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D. Rohrlich* What is nonlocal in “counterfactual
communication”?
14:20 - 15:05 45
G. Kar Quantum nonlocality does not demand all-out
randomness in measurement choice
15:05 - 15:40 35
A. Matzkin Strong and weak single particle nonlocality
induced by time dependent boundary conditions
15:40 - 16:15 35
Tea break (16:15 - 16:35)
Chair: P. K. PANIGRAHI
U. Sinha Correlated photonic qutrit pairs for quantum
information and communication
16:35 - 17:10 35
S. Sponer Measurement Uncertainty Relations: operator-
based, operational and information-theoretic
approaches studied in Neutron Optics
17:10 - 17:45 35
M. Banik Exclusivity principle and unphysicality of Garg-
Mermin correlation
17:45 - 18:05 20
Dinner (19:00 - 21:00)
6th
December 2017 Free day discussion session
7th
December 2017
Chair: A. JORDAN
L. Maccone* Quantum time and quantum spacetime 9:30 - 10:15 45
S. Ghosh Self-testing via nonlocality-without-inequality
arguments
10:15 - 10:50 35
E. Cavalcanti Bell and Kochen-Specker inequalities from no-
fine-tuning
10:50 - 11:25 35
Tea Break (11:25 - 11:45)
Chair: S. GHOSH
A. Majumdar Sharing of nonlocality 11:45 - 12:20 35
K. Edamatsu Nonlocal two-qubit measurement using spin
products
12:20 - 12:55 35
Lunch (12:55 - 14:15) Chair: A. MAJUMDAR
A. K. Pati* Tighter uncertainity and Reverse uncertainity
relation
14:15 - 15:00 45
F. Buscemi Secure Disposal of Information and Quantum
Private Decoupling
15:00 -15:35 35
Le Bin Ho Continuous pointer state approach to modular-value
amplification
15:35 - 15:55 20
POSTER SESSION (16:00-17:45)
CULTURAL PROGRAMME (18:00-19:30) CONFERENCE DINNER*#
(19:45 - 23:00)
8th
December 2017
Chair: A. K. PATI
A. Jordan* Strength in weakness: quantum trajectories,
foundations, and precision measurements
9:30 - 10:15 45
D. Sarkar Correlations in multipartite scenario 10:15 - 10:50 35
O. Maroney "What's Fine for Leggett & Garg? About
Macrorealisms & Measurement disturbances"
10:50 - 11:25 35
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Tea Break (11:25 - 11:50)
Chair: D. SARKAR
Arvind Protecting Quantum States of NMR Qubits 11:50-12:25 35
R. P. Singh Using non-separable state of light to find the
“lost” phase structure
12:25-13:00 35
Lunch (13:00 - 14:30)
Chair: M. GENOVESE
L. Vaidman* The past of a quantum particle 14:30 - 15:15 45
R. Shrikanth A quantum cryptographic route to the reality of
the quantum state
15:15 - 15:50 35
R. Rahman Quantum anonymous veto based on GHZ
correlations
15:50 - 16:25 35
Tea break (16:25 - 16:50)
Chair: G. KAR
J. Dressel Quantum Trajectories with Many Worlds 16:50 - 17:25 35
A. Avella Quantum measurement in weak coupling
regime: from non-contextuality in weak values to
protective measurements
17:25 - 18:00 35
Dinner (19:00 – 21:00)
9th
December 2017
Chair: L. VAIDMAN
M. Genovese* Time and quantum correlations: experimental
visualizations
9:30 - 10:15 45
A. Sen De Deterministic Quantum Dense Coding Networks 10:15 - 10:50 35
T. Qureshi Measuring Coherence in Multislit Interference 10:50 - 11:25 35
Tea Break (11:25 - 11:45)
Chair: ARVIND
N. Sakharwade Bidirectional Dense Coding and Teleportation in
Butterfly network
11:45 - 12:05 20
Aravinda S Combinatorial approach to non-classicality and
cryptographic security in single systems
12:05 - 12:25 20
R. Venkatrama Negations and Truth-Perspectives pertaining to
Qudits based Multi-valued Quantum Computational
Logics
12:25 - 12:45 20
G. Sharma Complementarity Relation for Coherence and
Disturbance
12:45 - 13:05 20
Closing Remark: 13:05 – 13:30
Lunch (13:30 - 14:30)
*Key note speaker
**Duration includes the time for discussions. The duration of discussions is 10 minutes for Keynote
speakers and 5 minutes for rest of the speakers. # Lunches (except 6
th December) will be served at the Conference Hotel (Panache Hotel) for all
participants. ##
Dinners (except 7th December) will be served at the same hotel/guest house where the
speaker/participant is accommodated.
**Conference Dinner will be served at the Hotel panache. All participants are invited to join.
ICQF-17 / 6
ICQF-17 / 7
TITLE AND ABSTRACTS
Invited Talks
Name G. S. Agarwal
Affiliation Texas A&M University, USA
Title Subradiance to Hyperradiance in Strong Coupling Cavity QED
Abstract The collective behavior of an ensemble of atoms has been studied in-depth since the
seminal paper of Dicke where he demonstrated that a group of emitters in collective
states is able to radiate with increased intensity a phenomenon that he called
superradiance. Almost all studies of superradiance since then have been in the weak
coupling regime of the interaction. The strong coupling which one can routinely
achieve in cavity QED can lead to a variety of new behavior starting from
subradiance to hyperradiance. We discuss various mechanisms behind
hyperradiance and possible nonclassical nature of the emitted radiation.
Name Arvind
Affiliation IISER-Mohali, India
Title Protecting Quantum States of NMR Qubits
Abstract The talk will describe our recent work on generation, estimation and preservation of
novel quantum states of two and three qubit NMR systems. Quantum states which
display quantum correlations play a key role in performing specific quantum
information processing tasks. We have prepared several types of correlated quantum
states which are quite fragile and implemented various types of preservation
schemes on them. We use several pulse sequences based on dynamical decoupling
schemes to decouple system-bath interactions, thereby suppressing the decoherence
of the state under study. Our schemes have important implications for the realistic
protection of delicate quantum states.
Name A. Avella
Affiliation INRIM, Turin, Italy
Title Quantum measurement in weak coupling regime: from non-contextuality in
weak values to protective measurements
Abstract Quantum mechanics, one of the keystones of modern physics, has an unprecedented
success in predicting the behavior of nature, leading to a perfect agreement between
theoretical predictions and experimental results in a vast amount of fields. However,
until this day, there is a strong debate about the foundational concepts of quantum
mechanics [1-4].
Weak value measurements have recently given rise to a great amount of interest in
both the possibility of measurement amplification and the chance for further
quantum mechanics foundations investigation. In particular, a question emerged
about weak values being proof of the incompatibility between quantum mechanics
and non-contextual hidden variables theories (NCHVTs). A test to provide a
ICQF-17 / 8
conclusive answer to this question was given by Pusey [5] where a theorem was
derived showing the NCHVT incompatibility with the observation of anomalous
weak values under specific conditions. We realized this proposal, clearly pointing
out the connection between weak values and the contextual nature of quantum
mechanics [6].
Another very intriguing aspect of quantum mechanics that we have investigated by
means of weak measurements is the fact that variables might not have definite
values. A complete quantum description provides only probabilities to obtain
various eigenvalues of a quantum variable. In particular, the expectation value is
known to be a statistical property of an ensemble of quantum systems. In contrast to
this paradigm, we demonstrate a unique method allowing to extract information
about the expectation value of a physical variable on a single particle with a single
measure. Our experimental implementation corresponds to the first realization of
the quantum protective measurement [7][8].
Reference:
[1] M. F. Pusey et al., Nat. Phys. 8, 475 (2012).
[2] L. Hardy, Int. J. Mod. Phys. B 27, 1345012 (2013).
[3] M. Ringbauer et al.; Nat. Phys. 11, 249 2015).
[4] M. Genovese; Adv. Sci. Lett. 3, 249 (2010).
[5] M. F. Pusey; Phys. Rev. Lett. 113, 200401 (2014).
[6] F. Piacentini et al., Phys. Rev. Lett. 116 (18), 180401(2016).
[7] Y. Aharonov and L. Vaidman; Phys. Lett. A 178, 38 (1993).
[8] F. Piacentini et al.; Nature Physics doi:10.1038/nphys4223 (2017).
Name Subhashish Banerjee
Affiliation IIT Jodhpur
Title Aspects of Non-Markovianity In Quantum Walks
Abstract After motivating the need for a study of Open Quantum Systems, we introduce,
briefly, quantum operations and use it to discuss a few well known noise
processes. We then move to some recent developments in the efforts to understand
non-Markovian phenomenon. Our discussion about non-Markovian behaviour will
be made in the backdrop of some well-known non-Markovian processes. We show
how different sources of non-Markovianity could be disambiguated. All this is
done using the platform of Quantum Walks.
Name C. Branciard
Affiliation Institute of Neel, Grenoble, France
Title Multipartite quantum processes and correlations with no definite causal order
Abstract The notion of causality is deeply rooted in our understanding of the world we live
in: we typically understand the relationship between events in terms of causal
relations, where some earlier events are causes for later events. Now, we know that
the quantum world is full of weird phenomena. Cats can be in indefinite states, in a
quantum superposition of being alive and dead. It has been realised recently that
causal relations themselves can be indefinite, in some kind of quantum
superposition. However, a good understanding of quantum processes with indefinite
causal order, and of the correlations they may generate is still missing. In this talk I
will describe recent research on those new concepts, with a special focus on the
subtleties that arise in the multipartite case.
ICQF-17 / 9
Name F. Buscemi
Affiliation Nagoya University, Japan
Title Secure Disposal of Information and Quantum Private Decoupling
Abstract Correlations between an "object system" (accessible) and a "reference system"
(inaccessible) can be understood as the amount of information that one possesses
about the reference. When faced with the problem of erasing such information
(correlations), the direct approach is "to dump" them in the environment, that is,
hand them over to an eavesdropper. In order to give a model-independent
description of secure information disposal, I propose here the paradigm of "private
quantum decoupling," where the goal is to decouple the system from the reference,
by acting locally on the system and, at the same time, maintaining its local
environment decoupled from the reference.
In this framework, the concept of private local randomness naturally arises as a
resource, and total correlations are divided into "extrinsic" (disposable) and
"intrinsic" (non-disposable) ones. I show upper and lower bounds on the amount of
intrinsic correlations present in an arbitrary bipartite state, and show that, in
tripartite pure states, they satisfy a monogamy constraint, making apparent their
quantum nature. A relation with entanglement theory is provided, by showing that
intrinsic correlations constitute an entanglement parameter. Finally, I compute the
regularized intrinsic correlations and show that these equal the coherent
information, which is thus equipped with a new operational interpretation. This
implies, in particular, that separable correlations are all extrinsic. Reference: F.
Buscemi, "Private Quantum Decoupling and Secure Disposal of Information." New
J. Phys., vol. 11, 123002 (2009).
Name P. Busch
Affiliation University of York, UK
Title Quantum Uncertainty Regions – Theory and Experiment
Abstract Recent break-through results in the rigorous formulation of the joint measurement
aspect of Heisenberg’s uncertainty principle (which I reviewed in my talk at
ICQF15) have led to a boost of research activity into finding novel variants of
measurement uncertainty relations. Here I discuss the most comprehensive and
stringent way of casting such relations, namely in the form of uncertainty regions. I
will explain this concept, give examples both for preparation and measurement
uncertainty, and describe some recent experimental confirmations.
Name E. Cavalcanti
Affiliation Griffith University, Australia
Title "Bell and Kochen-Specker inequalities from no-fine-tuning"
Abstract Nonlocality and contextuality are at the root of conceptual puzzles in quantum
mechanics, and are key resources for quantum advantage in information-processing
tasks. Bell nonlocality is best understood as the incompatibility between quantum
correlations and the classical theory of causality, applied to relativistic causal
structure. Contextuality, on the other hand, is on a more controversial foundation.
In this work, I provide a common conceptual ground between nonlocality
and contextuality as violations of classical causality. First, I generalise a recent
work by Wood and Spekkens, who showed that all causal models for certain Bell-
inequality violations require fine-tuning of its causal parameters -- regardless of the
underlying causal structure. Here I show this result holds without two of the original
ICQF-17 / 10
assumptions, applies to all (bipartite) cases of Bell nonlocality, and remarkably,
does not require any extra assumption related to "free choice" or independence
between hidden variables and measurement settings, unlike all other derivations of
Bell inequalities. As a consequence, it can be applied to contextuality scenarios: all
causal models for violations of a Kochen-Specker-contextuality inequality
(involving two measurements per context) require fine-tuning. Thus the quantum
violation of classical causality goes beyond the case of space-like separated
systems, and manifests already in scenarios involving single systems.
Name Justin Dressel
Affiliation Chapman University, USA
Title Quantum Trajectories with Many Worlds
Abstract The usual formulation of quantum trajectory theory seems distinct from the standard
quantum theory at face value, since it involves stochastic master equations that
modify the unconditioned unitary dynamics. A careful analysis of a realistic
continuous measurement for a superconducting qubit corrects this misconception,
and highlights interesting subtleties like delayed choice measurements that are
hidden in the standard treatment. This analysis also makes clear how to understand
such a measurement from a purely unitary many worlds perspective.
Name K. Edamatsu
Affiliation Tohoku University, Japan
Title Nonlocal two-qubit measurement using spin products
Abstract A simple protocol for nonlocal and generalized two-qubit measurement is proposed.
It consists of measurements of nonlocal spin product operators [1] with the help of
shared entanglement as an ancillary resource. The protocol also realizes complete
and deterministic Bell state measurement between a pair of distant qubits, as well as
a complete Bell filter that transmits either one of the Bell states indicated by the
measurement outcome [2]. These schemes can be implemented using photon
polarization qubits by which measurement uncertainty relation for a single qubit is
investigated [3].
References
[1] A. Brodutch and E. Cohen, Phys. Rev. Lett. 116, 070404 (2016).
[2] K. Edamatsu, arXiv:1612.0857.
[3] K. Edamatsu, Phys. Scr. 91, 073001 (2016).
Name Marco Genovese Affiliation NRIM, Turin, Italy Title Time and quantum correlations: experimental visualizations
Abstract Quid est ergo tempus? si nemo ex me quaerat, scio; si quaerenti explicare velim,
nescio 1
As Aurelius Augustinus everybody has a clear perception of what time is, but a
clear physical definition of what it is still remains a debated task. The ―problem of
time‖ in present physics substantially stems from the fact that a straightforward
quantization of the general relativistic evolution equation and constraints generates
for the Universe wave function the Wheeler-De Witt equation [1], which describes
a static Universe. Page and Wootters [2] considered the fact that there exist states
of a system composed by entangled subsystems that are stationary, but one can
interpret the component subsystems as evolving: this leads them to suppose that the
global state of the universe can be envisaged as one of this static entangled state,
whereas the state of the subsystems (us, for example) can evolve.
Here I present two experiments addressed to visualise this phenomenon. The first is
ICQF-17 / 11
based on PDC polarisation entangled photons that allows showing with a practical
example a situation where this idea works, i.e. a subsystem of an entangled state
works as a "clock" of another subsystem [3]. However, the simple original Page and
Wootters model needs some extension for describing several time measurements
[4]. Similarly, in our first experiment the Use of a two-dimensional clock implies
that the time is discrete, periodic and can take only two values: 0 and 1. In a second
experiment [5], that I present here for the first time, we use a continuous system (the
position of a photon) to describe time, which gives us access to measurements at
arbitrary times and hence arbitrary two-time correlations.
[1] C.Rovelli, quant-gr0006061
[2] D.N. Page and W.K. Wootters, Phys. Rev. D 27, 2885 (1983); W.K. Wootters,
Int. J. Theor. Phys. 23, 701 (1984).
[3] E.Moreva,M.Gramegna,G.Brida,L.Maccone,M.Genovese, Phys. Rev. A 89,
052122 (2014).
[4] V.Giovannetti, S.Lloyd, L.Maccone, Phys. Rev. D, 92, 045033 (2015).
[5] E.Moreva, M.Gramegna, G. Brida, L. Maccone and M.Genovese, Phys. Rev.D
in press. (arXiv:1710.00707) 1What is the time? If nobody ask me, I know; whether I want to explain it to
somebody, I do not know.
Name Partha Ghose Affiliation INSA New Delhi, India Title Quantum and Classical Mechanics: Building A Bridge
Abstract It is first shown that when the Schrodinger equation for a system is written in the
Hamilton-Jacobi form, complete information about the system's quantum-ness is
separated out in a single term Q, the so called `quantum potential'. Based on this, an
operator formulation of classical statistical mechanics using complex wave
functions spanning a Hilbert space is then proposed, and its similarities and
differences with quantum mechanics are pointed out. The formulation goes beyond
standard classical statistical mechanics in predicting coherent superpositions of
classical states that do not exhibit any interference patterns and challenge deeply
held notions of classical-ness, quantum-ness, entanglement, macro realism and the
significance of violations of Bell-like and Leggett-Garg inequalities. It also provides
a more secure foundation to delve deeper into the area of quantum-classical
correspondence and information processing than exists at present.
Name Sibashish Ghosh Affiliation IMSc Chennai, India Title Self-testing via nonlocality-without-inequality arguments
Abstract Given any entangled state of a bipartite quantum system, shared between two far
apart parties, what is the best task it can offer? Self-testing provides one kind of
solution for such a task in the sense that if such a state is pure, it will violate a local-
realistic inequality maximally. Such an inequality -- referred
to as a `tilted Bell inequality' -- depends on a parameter which, in turn, depends on
the entanglement of the given pure state. Considering Hardy-type nonlocality-
without-inequality argument for two dichotomic measurement settings per site, we
provide here self-testing for any given two-qubit non-maximally entangled pure
state -- by appending at most one extra condition on the observed joint probabilities.
Similarly, by appending at most two extra conditions on the observed joint
probabilities, we provide here Cabello-type self-testing argument for any such state.
Finally, we try to provide a comparison of strengthness of the aforesaid self-testing
protocol with the associated protocol(s) expressed in terms of corresponding local-
realistic inequality.
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Name Holger F. Hofmann Affiliation Hiroshima University, Japan Title Superpositions of causality: an analysis of the mechanisms of control in the
quantum limit
Abstract Experimentally, quantum state preparation and measurement require extreme levels
of control over the dynamics of quantum systems. As a result, the procedures of
state preparation and measurement seem to produce separate "contextual" realities
of the same system, with paradoxical statistical relations between these separate
realities. Although much progress has been made to identify non-classical features
of quantum statistics, quantum theory only describes these phenomena, without
providing any satisfactory explanation in the form of unifying concepts or
principles. Here, I present a possible solution to the problem based on the
description of non-classical statistics by weak values and Dirac distributions. The
key to non-classical features is then found in the complex phases that relate the
effects of quantum interferences to reversible transformations of quantum states and
their associated statistics. I will argue that this relation provides us with a non-trivial
explanation of quantum physics that can resolve fundamental questions about the
origin and nature of quantum phenomena such as entanglement and quantum jumps.
In particular, this new perspective on quantum physics should motivate us to
investigate the actual processes involved in state preparation and the role played by
the physics of control in the available quantum technologies, significantly
improving our understanding of large scale quantum processes.
Reference: [1] H. F. Hofmann, "Quantum paradoxes originating from the nonclassical statistics
of physical properties related to each other by half-periodic transformations," Phys.
Rev. A 91, 062123 (2015).
[2] H.F. Hofmann, "On the fundamental role of dynamics in quantum physics," Eur.
Phys. J. D 70, 118 (2016).
[3] H. F. Hofmann "Quantum interference of position and momentum: A particle
propagation paradox," Phys. Rev. A 96, 020101(R) (2017).
Name Dipankar Home Affiliation Bose Institute, Kolkata, India Title Generalised Weak Measurement assisted Remote State Preparation and
Demonstration of Hidden Nonlocality
Abstract Taking cue from the standard weak measurement scenario, we generalise it by
introducing a finite strength coupling between an ancilla and one of the members
(referred to as Alice) of spatially separated correlated particles, followed by
postselection through projective measurement on the ancilla. Corresponding to each
postselected outcome on Alice’s side, we find that the state of the other member
(referred to as Bob) of the spatially correlated system can be prepared very close to
a target state of Alice’s choice. By choosing an appropriate fidelity measure that is
averaged over all pure target states on Alice’s side, we show that this protocol can
implement remote state preparation giving quantum advantage for all Bell diagonal
states.
A further significance of the novel scenario used for the above suggested remote
state preparation scheme is that it can also be used to reveal hidden nonlocality for a
class of bipartite qubit states that do not initially exhibit nonlocality. Indications will
be given of further studies for probing the usefulness of such a scheme.
ICQF-17 / 13
Name Andrew N. Jordan Affiliation University of Rochester, USA Title Strength in weakness: quantum trajectories, foundations, and precision
measurements
Abstract This overview talk will outline recent developments in quantum theory and
experiment, focusing on weak and continuous measurements. I will discuss the
basic theory behind this field, highlighting the recent stochastic path integral
approach to continuous measurements and the experiments now able to be routinely
done in order to check the accuracy of the theory. I will also discuss some of the
applications of this area of research, such as parameter estimation, state
tomography, and error correction. Finally, some foundational questions addressed
by this field of study will be raised, such as the simultaneous measurement of
noncommuting observables.
Name Guruprasad Kar Affiliation ISI Kolkata, India Title Quantum nonlocality does not demand all-out randomness in measurement
choice Abstract Nonlocality is one of the most intriguing features of quantum mechanics. John Bell,
in his seminal work of 1964, proved that local-realism imposes a bound on the
correlations among the measurement statistics of distant observers. Surpassing this
bound rules out the possibility of local-realistic description of microscopic
phenomena. For detecting Bell-nonlocality, it requires, in the simplest scenario, two
measurements to be performed randomly by each of the two distant observers. In
this work, we propose a novel framework where three measurements, two on
Alice’s side and one on Bob’s side, suffice to reveal quantum nonlocality and hence
does not require all-out randomness in measurement choice. Our method relies on a
very naive operational task in quantum information theory, namely, the minimal
error state discrimination. As a practical implication, this method constitutes an
economic entanglement detection scheme, which uses a less number of entangled
states compared to all such existing schemes. Moreover, the method applies to a
class of generalized probability theories containing quantum theory as a special
example.
Name Y-C. Liang Affiliation National Cheng Kung University, Taiwan Title What can we learn from the apparent violation of the nonsignaling conditions?
Abstract The device-independent approach to physics is one where conclusions are drawn
directly and solely from the observed correlations between measurement outcomes.
This operational approach to physics arose as a byproduct of Bell's seminal work to
distinguish quantum correlations from the set of correlations allowed by a particular
class of physical theories, namely, locally-causal theories. In practice, since one can
only perform a finite number of experimental trials, deciding whether an empirical
observation is compatible with some class of physical theories will have to be
carried out via the task of hypothesis testing.
In this talk, I will review some recent progress on this task based on the prediction-
based-ratio method and discuss how it may allow us to determine the statistical
evidence against some other classes of physical theories, such as those constrained
only by the nonsignaling principle, and those that are constrained to produce the so-
called "almost-quantum" set of correlations. As an application, we demonstrate how
this method allows us to unveil the apparent violation of the nonsignaling
ICQF-17 / 14
conditions in certain experimental data. The implication of this apparent violation
will be briefly discussed.
Name Lorenzo Maccone Affiliation Universita' di Pavia, Italy Title Quantum time and quantum spacetime
Abstract We give a consistent quantum description of time, based on Page and Wootters'
conditional probabilities mechanism, that overcomes the criticisms that were raised
against similar previous proposals. In particular we show how the model allows to
reproduce the correct statistics of sequential measurements performed on a system
at different times. We also give a mechanism to construct a quantum spacetime by
evaluating space and time through quantum rods and clocks. It provides a
framework to treat time and space as homogeneous degrees of freedom. To this
aim, we introduce the state of the system conditioned on a position in space whereas
the conventional formulation of quantum theory considers only states that are
conditioned on time.
Name Archan Majumdar Affiliation SNBCS Kolkata, India Title Sharing of nonlocality
Abstract We address the question as to whether the nonlocality of a single member
of an entangled pair of spin 1/2 particles can be shared among multiple observers on
the other wing who act sequentially and independently of each
other. We first show that the optimality condition for the trade-off between
information gain and disturbance in the context of weak or non-ideal measurements
emerges naturally when one employs a one-parameter class of positive operator
valued measures (POVMs). Using this formalism we then prove analytically that it
is impossible to obtain violation of the Clauser-Horne-Shimony-Holt (CHSH)
inequality by more than two Bobs in one of the two wings using unbiased input
settings with an Alice in the other wing. We finally consider the steering scenario
for two-qubits with two measurement settings for each observer. We show that the
Cavalcanti Foster-Fuwa-Wiseman (CFFW) inequality can be violated for an Alice
and at most two Bobs on the other side.
Name Owen Maroney Affiliation Oxford University, UK Title "What's Fine for Leggett and Garg? About Macrorealisms and Measurement
disturbances."
Abstract "In recent years the precise control involved in quantum measurements has allowed
the testing of Leggett-Garg Inequality violations in microscopic systems, and a
renewed interest in understanding precisely what such a violation implies. Doubts
have been raised whether such violations are a problem for macrorealism, as
Leggett and Garg thought, or are just a problem for non-invasive measurements,
and whether the Leggett Garg Inequalities themselves could be replaced with better
tests.
I will attempt to bring some clarity to this issue by presenting a root theorem that
incorporates both the Leggett-Garg Inequality and some of the suggestions for
replacing it, and argue that it is the possibility of an explanation in terms of non-
invasive measurements that is at stake in these tests. However, I will also show that
whenever a non-invasive explanation is possible, then a macrorealist non-invasive
model is also possible. This is analogous to the situation with Bell's inequality,
where it is local causality, rather than hidden variables, that is at stake, but that
whenever a locally causal explanation is possible, a locally causal hidden variable
ICQF-17 / 15
model is also possible. Finally I will show how macrorealism is no more committed
to non-invasive measureability than hidden variables are restricted to be locally
causal, and will briefly discuss how wider classes of macrorealist theories may yet
be experimentally ruled out by different kinds of experimental tests."
Name Paolo Mataloni Affiliation University Sapienza Of Rome, Italy Title Weak and strong non-Markovianity
Abstract The simulation of non-Markovian dynamics and the test of its main features have
been object of several experimental works in the last years, with relevant examples
mainly based on the use of all-optical systems. Generally, non-Markovian regimes
featuring environment to system backflow of information (strong non-
Markovianity) have been experimentally simulated. Using an all-optical setup we
have experimentally emonstrated the so-called regime of weak non-Markovianity
occurring even in absence of information backflow from the environment to the
system. In a further experiment we have studied non-Markovianity of open quantum
systems based on the so-called collisional model where the continuous time
evolution of an open quantum system is replaced by a stroboscopic one. I will
present the theoretical and experimental results obtained in the case of single and
two-photon entangled state evolution.
Name Alex Matzkin Affiliation CNRS, Univ. Cergy-Pontoise, France
Title Strong and weak single particle nonlocality induced by time dependent
boundary conditions
Abstract We investigate the issue of single particle nonlocality in a quantum system
subjected to time-dependent boundary conditions. First, we will see that contrary to
earlier claims, there is no strong nonlocality: a quantum state localized at the centre
of a well with moving walls is not modified by the wall's motion. We then show the
existence of a weak form of nonlocality: when a quantum state is extended over the
well, the wall's motion induces a current density all over the box instantaneously.
We indicate how this current density can in principle be measured by performing
weak measurements of the particle's momentum. We will also see how the wall's
motion generates the existence of a global geometric phase at every point of the
box.
Name P. Panigrahi Affiliation IISER-Kolkata, India Title Quantum coherence, Holevo Bound and Quantum Discord
Abstract We explicate the relationship between the information theoretic quantities in
quantum mechanics: quantum coherence, quantum discord and Holevo bound. The
main result of our paper can be summarized by the following two points:
• Equivalence of loss of information and loss of coherence: A physically
motivated resource theory of coherence under operations which do not use
coherence has been recently proposed. The operations which do not use coherence
have been identified as strictly incoherent operations [2]. We considered the task of
classical communication using quantum ensemble { } when the receiver is only
allowed to perform strictly incoherent operation and demonstrated the equivalence
between the loss of information about ( ) and the loss of
coherence due to mixing ∑ ( ) (∑ ) , according to relative entropy
measure of coherence. Here, is the Holevo Bound.
ICQF-17 / 16
• Complementarity of quantum discord and accessible information: We
consider a separable bipartite system ∑ , and proved that the
basis dependent quantum discord is bounded above by the loss of coherence on
Bob’s side; ∑ ( ) (∑ ) . We employed this relation to prove the
complementarity of quantum discord and accessible information on Bob’s side;
( ) ( ). Here, is the optimal measurement for
which accessible information is maximum on Bob’s ensemble. Hence, if Holevo
bound is achievable by performing certain measurement on Bob’s side, quantum
discord will be equal to zero.
Reference:
[1] A. K. Goswami, P. K. Panigrahi. arXiv:1703.08700.
[2] B.Yadin, J. Ma, D. Girolami, M. Gu, V.Vedral, Phys. Rev. X, 6, 041028 (2016).
Name A.K. Pati Affiliation HRI, Allahabad, India Title Tighter Uncertainty and Reverse Uncertainty Relations
Abstract We prove a few novel state-dependent uncertainty relations for product as well the
sum of variances of two incompatible observables. These uncertainty relations are
shown to be tighter than the Roberson-Schrodinger ¨ uncertainty relation and other
ones existing in the current literature. Also, we derive state dependent upper bound
to the sum and the product of variances using the reverse Cauchy-Schwarz
inequality and the Dunkl-Williams inequality. Our results suggest that not only we
cannot prepare quantum states for which two incompatible observables can have
sharp values, but also we have both, lower and upper limits on the variances of
quantum mechanical observables at a fundamental level.
Name Marcin Pawlowski Affiliation University of Gdańsk, Poland Title Random access codes - a review
Abstract Random access codes are one of the simplest communication tasks in which
quantum advantage can be witnessed. They have been formally introduced over a
decade ago but implicitly they were used even earlier. They have many applications
due to their simplicity and ease of generalization. The former also enabled many
teams to perform experimental realizations of them. In this review I will define the
codes formally and them describe many of their possible generalizations. For each
of them I will discuss applications which include: foundations of physics,
cryptography, computer science and pure mathematics.
Name Tabish Qureshi Affiliation Jamia Milia University, Delhi, India Title Measuring Coherence in Multislit Interference
Abstract A quantitative measure of quantum coherence was recently introduced in the
context of quantum information theory. This measure has also been argued to be a
good quantifier of the wave nature of quantum objects. However, actually
measuring coherence in an experiment is still considered a challenge. A procedure
for measuring coherence in a multislit interference is proposed here. It can be used
for experimentally testing duality relations for interference experiments involving
more than two slits.
ICQF-17 / 17
Name S. M. Roy Affiliation HBCSE, TIFR, Mumbai, India Title Contractive Quantum States
Abstract I prove rigorous quantum limits on contractive and expanding states of a free mass
and of an oscillator. Since a free electromagnetic field and a free boson field have
Hamiltonians which are sums of oscillator Hamiltonians with different frequencies,
there are immediate applications to such fields. In particular limits on contractive
and expanding quadratures of the electromagnetic field follow. The limits are
shown to be optimum by constructing states which saturate the limits.
Name Daniel Rohrlich Affiliation Ben Gurion University of the Negev, Israel Title What is nonlocal in “counterfactual communication”?
Abstract We present a paradox in which a neutron and a mirror exchange weak modular
angular momentum <Lz mod 2ħ >w even though there seems to be no local
interaction that could allow them to exchange <Lz mod 2ħ >w. We then demonstrate
that the neutron and mirror do interact locally, via a local current of Lz mod 2ħ.
However, Lz mod 2ħ is itself a nonlocal quantity. In this sense, we invert the
―interaction-free measurement‖ of Elitzur and Vaidman, in which two local
quantities (the positions of a photon and a bomb in the two arms of a Mach-Zehnder
interferometer) interact nonlocally; we exhibit it, instead, as two nonlocal quantities
(the modular angular momentum of a neutron and of a mirror) that interact locally
via their weak currents. We apply our result to show that so-called counterfactual
quantum communication arises from local interaction via a massless local current.
Name Ramij Rahaman Affiliation Allahabad University, India Title Quantum anonymous veto based on GHZ correlations
Abstract Anonymous Veto (AV) is one of the basic primitive for the cryptographic problems
like Dining cryptographers (DC) where the main aim is to hide the identity of the
senders of the messages. It can be achieved by classical methods where the security
is based either on computational hardness or on shared private keys. In this regard,
we present a secure quantum protocol for the AV problem by exploiting the GHZ
correlations. First, we solve a generalized version of the DC problem with the help
of multiparty GHZ state. This allow us to provide a secure quantum protocol for the
AV. Security of our protocol rely on some novel and fundamental features of GHZ
correlations related to quantum nonlocality.
Name Debasis Sarkar
Affiliation Calcutta University, India
Title Correlations in multipartite scenario
Abstract The increase in the number of non-interacting particles (N) together with use of
multipartite entanglement in an entanglement swapping network basically motivates
our present topic of discussion. To be specific, here we firstly focus on tripartite
entangled states. However, the discussion can be extended for $n-$ partite entangled
states. For our purpose we will introduce a general network scenario involving five
parties and three independent sources. We define such a network, characterized by
five partite correlation terms as a trilocal network scenario. We design a set of Bell-
type inequalities necessarily satisfied under source independence assumption known
as trilocal assumption. There exist families of tripartite entangled quantum states,
both pure and mixed which can generate nontrilocal correlations and hence capable
of exhibiting nonlocality (apart from standard Bell sense). Interestingly, genuine
entanglement is not a necessary requirement for generation of nontrilocality in a
ICQF-17 / 18
quantum network. This form of nonclassical phenomenon can also be observed in a
network using biseparable quantum states. Now, analyzing shareability of
correlations arising in any physical theory may be considered as a fruitful technique
of studying the theory. We will also discuss here an analogous approach of studying
quantum theory. For our purpose, we have deviated from the usual procedure of
assessing monogamous nature of quantum correlations in standard Bell-CHSH
scenario. We have considered correlations arising in a quantum network involving
independent sources. Precisely speaking, we will discuss monogamy of nonbilocal
correlations by deriving a relation restricting marginals.
Name Aditi Sen De Affiliation HRI, Allahabad, India
Title Determinstic Quantum Dense Coding Networks
Abstract I will talk about the scenario of deterministic classical information transmission
between multiple senders and a single receiver, when they a priori share a
multipartite quantum state -- an attempt towards building a deterministic dense
coding network. Specifically, I will show that in case of two or three senders and a
single receiver, generalized Greenberger-Horne-Zeilinger (GHZ) states are not
beneficial for sending classical information deterministically beyond the classical
limit, except when the shared state is the GHZ state. On the other hand, three and
four qubit generalized W states with specific parameters as well as the four qubit
Dicke states can provide quantum advantage in deterministic dense coding.
Name R.P. Singh
Affiliation PRL Ahmedabad India
Title Using non-separable state of light to find the “lost” phase structure
Abstract We generate optical vortices of different orders and scatter them through random
scattering media. We show that vortices can be recovered even after scattering with
far reaching applications in optical communication.
Name Urbashi Sinha Affiliation RRI, Bangaluru, India Title Correlated photonic qutrit pairs for quantum information and communication
Abstract In this talk, I will discuss ongoing experiments in our lab which deal with spatially
correlated photonic qutrits towards applications in quantum information and
communication. While twodimensional quantum systems known as qubits are
traditionally used for experiments in Quantum Computation, we are exploring
higher dimensional quantum systems called qudits. Maximally entangled qudits are
subjects of interest in many quantum information protocols and fundamental tests of
quantum mechanics. Transverse spatial correlation obtained from spontaneous
parametric down converted photons is one of the simplest methods that could be
readily implemented using slit based interferometric systems [1]. Recently, it was
shown that, the angular spectrum of the incident pump can be transferred to the
signal-idler bi-photon pair in SPDC process. Tapping on to this, we attempt to
harness qutrit- qutrit correlations in spatial degrees of freedom by making the pump
have a profile of a triple slit. We study how the idler profile is correlated with a
given signal and establish the qutrit-qutrit correlations for different experimentally
viable parameters [2]. Very recently, we have also been able to certify and quantify
entanglement between the qutrits, thus opening up a plethora of possibilities in
foundations based studies as well as quantum information based explorations. This
principle of generating spatially entangled photon qutrits could be easily extended
to n dimensional space and find wide applications, especially in Quantum
Computing. Demonstrating spatial correlations between two qutrits paves the way
ICQF-17 / 19
for using the spatial degree of freedom in experiments based on long distance
Quantum Communication. While our experiment is a proof of principle experiment
which demonstrates that spatial correlations can be quantified between qutrits, the
result will also be applicable when the photons are in larger physical separation than
inside the lab domain.
[1]P.Kolenderski, U.Sinha, M.Youning, T.Zhao, M.Volpini, A.Cabello,
R.Laflamme, T.Jennewein, Physical Review A 86 012321, (2012).
[2] D.Ghosh, T.Jennewein, P.Kolenderski, U.Sinha, arXiv: 1702.02581
Name Yutaka Shikano Affiliation Tokyo Institute of Technology, Japan Title Quantum Phase through Quantum Tunneling
Abstract The quantum tunnelling is one of the unique quantum-mechanical phenomena but
does not be well understood. In this talk, the quantum phase through quantum
tunnelling will be discussed physically and mathematically, respectively.
Name Stephan Sponar Affiliation Atominstitute, Vienna, Austria Title Measurement Uncertainty Relations: operator-based, operational
& information-theoretic approaches studied in Neutron Optics
Abstract Heisenberg’s uncertainty principle is without any doubt one of the corner stones of
modern quantum physics. However, the present perception of quantum mechanics
has deviated from Heisenberg’s empiristic assumptions, reflected in his famous
gamma-ray microscope where a measurement process is the source of uncertainty,
resulting in a version of the uncertainty relation expressed as a product of widths of
probability distributions, i.e., standard deviations (independent of any
measurement). These types of uncertainty relations set limits on how sharp the
values of two observables can be determined if measured separately, but provide no
information of the error when measuring one observable and the thereby induced
disturbance on another subsequently measured observable. However, a naive
product-type error-disturbance uncertainty relation (EDUR) is not valid in general.
In 2003, Ozawa thus proposed an improved EDUR, based on rigorous and general
theoretical treatments of quantum measurements which is usually referred to as an
operator-based approach. In my talk, I will give an overview of our neutron optical
approaches for investigation of EDUR via successive measurements of
incompatible neutron spin observables.
Another more recent experiment tests so called operational definitions of error and
disturbance developed by Busch and his co-workers. In this theoretical framework
error and disturbance are evaluated from the difference between output probability
distributions of the successive measurement and reference (ideal) measurements.
Despite the ongoing controversy of the two competing approaches, in the case of
projectively measured qubit observables, such as neutron spin components, both
approaches lead to the same outcomes.
In our most recent experiment information-theoretic, or entropic, definitions of error
(in this theoretical framework referred to as noise) and disturbance are studied.
Here, noise and disturbance are defined via correlations between the input states and
measurement outcomes. We successfully carried out an experimental test of a
newly derived, tight noise disturbance uncertainty relation for general qubit
measurements. For certain non-commuting spin observables, the tight relation is
saturated with projective measurements. However, there are also cases in which the
ICQF-17 / 20
relation is only tight for general quantum measurements (i.e., positive-operator
valued measures), as predicted theoretically by Branciard.
Name R. Srikanth Affiliation PPISR, Bangalore, India. Title A quantum cryptographic route to the reality of the quantum state
Abstract The insecurity of quantum bit commitment (QBC) in the standard non-relativistic
quantum cryptographic framework is a consequence of quantum (and more
generally, nonclassical) steering. We identify assumptions in the standard argument,
by relaxing which, the committer's malicious steering operation can be rendered
either indeterminable or inexistent. Further, we propose a QBC protocol in a
quantum teleportation setting, whose security would, without appeal to an
ontological framework, entail the reality of the quantum state, assuming the
exclusion of retro causality. Interestingly, this only requires remote steering and not
nonlocality, allowing our argument to be adapted to provide an ontological
interpretation even for Spekkens' toy model (101) in support of an epistemic
interpretation of quantum states!
Name A.R. Usha Devi Affiliation Bangalore University, India Title Asymptotic limit of diffusive quantum trajectories
Abstract Every record of detection (measurement data) made on the environmental system
determines a trajectory in the state space of a quantum system interacting with the
environmental system [1]. Averaging over all possible measurement record results
in the Gorini-Kossakawsi-Sudarshan-Lindblad (GKSL) master equation [2],
describing dissipative irreversible evolution of the quantum system. It has been
identified that Quantum trajectories, resulted via continuous monitoring on the
environmental system, are solutions of non-linear stochastic Schrodinger equations,
where continuous time detection records are modelled as random classical noise
processes [3]. In particular, quantum diffusive trajectories describe Brownian
motion of a quantum state in the Hilbert space. Early 80’s witnessed a renewed
interest in developing the theory of continuous time observations on a quantum
system interacting with an environment [4]. Quantum state trajectory approach
attracted further attention in the context of quantum measurement theory [5]. In this
talk I outline the historical origin of quantum stochastic evolution leading to a
quantum state diffusion equation and discuss its asymptotic limit [6].
Reference:
[1] E. Davies. Quantum Theory of Open Systems (Academic Press, 1976); M. D.
Srinivas and E. B. Davies, Opt. Acta 28 981 (1981).
[2] V. Gorini, A. Kossakowski, and E. C. G. Sudarshan, J. Math. Phys. 17, 821
(1976); G. Lindblad, Commun. Math. Phys. 48, 119 (1976).
[3] L. Diosi, Phys. Lett. A 129, 419 (1988); N. Gisin, and J. Percival, J. Phys. A
167, 315 (1992).
[4] R. L. Hudson, and K. R. Parthasarathy, Commun. Math. Phys. 93, 301 (1984);
K. R. Parthasarathy, An Introduction to Quantum Stochastic Calculus, (Birkhauser,
1992).
[5] V. Belavkin, Radiotekh. Electron. 25, 1445 (1980); A Barchielli, Phys. Rev. A
34, 1642 (1986); H. M. Wiseman, G. J. Milburn, Quantum Measurement and
Control (Cambridge University Press, 2010).
[6] K. R. Parthasarathy and A. R. Usha Devi, J. Math. Phys. 58, 082204 (2017); K.
R. Parthasarathy and A. R. Usha Devi, arXiv:1707.08157v2.
ICQF-17 / 21
Name Lev Vaidman Affiliation Tel Aviv University, Israel Title The past of a quantum particle
Abstract Textbooks of quantum mechanics lack the concept of the past of quantum systems.
Few years ago I proposed to define the past of a quantum particle according the
trace it leaves. While in many cases this definition provides a reasonable
description, for a nested Mach-Zehnder interferometer it leads to a picture
seemingly contradicting common sense: the particle leaves a trace in a place
through which it could not pass. I will discuss recent theoretical and experimental
studies of this controversial issue.
ICQF-17 / 22
Contributed Talks
Name Manik Banik Affiliation IMSc, Chennai, India Title Exclusivity principle and unphysicality of Garg-Mermin correlation
Abstract We address the question of physical realizability of a probability distribution.
Specker first pointed out that this question cannot be answered from Kolmogorov’s
axioms alone. In the recent past, this observation of Specker has motivated simple
principles (exclusivity principle/ local orthogonality principle) that can explain
quantum limitations on possible sets of experimental probabilities in nonlocality
and contextuality experiments. We study Specker’s observation in the simplest
scenario involving three inputs each with two outputs. Then using only linear
constraints imposed on joint probabilities by this principle we show unphysicality of
a correlation introduced by Garg and Mermin as a counterexample to a suggestion
of Fine that if the inequalities of Clauser and Horne hold, then there exists a hidden-
variable model for a spin-1/1 correlation experiment of the Einstein-Podolsky-
Rosen type. Our result establishes limitation of a recent claim made by different
group of researchers that local orthogonality principle at single copy level is
equivalent to the no-signaling condition.
Name Le Bin Ho Affiliation Osaka University, Osaka, Japan Title Continuous pointer state approach to modular-value amplification
Abstract In quantum mechanics, the concept of quantum modular values allows for the
description of a quantum system in pre- and post-selection states. This manner has
been studied so far theoretically and experimentally, but most of the studies carried
out to date are in discrete pointers. Here, we present a modular-value version in
which the measurement pointer is described in a continuous Gaussian state. We
show that the conditional post-selection probability of obtaining the momentum is
described and amplified by the modular value. Furthermore, to clarify the advantage
of the modular-value amplification (MWA), we discuss the momentum shift and the
signal-to-noise ratio (SNR) of a measured observable in the system and its
optimization. This might guide for the study of modular values with various
classical and nonclassical pointer states, as well as further investigations of the
optimal pointer states for MWA.
Name Claude Klöckl Affiliation IQOQI Vienna, Austria Title On the complementarity between monogamy of correlations and entropy
inequalities in the Bloch picture
Abstract We exploit the Bloch vector formalism to study the seemingly unrelated areas of
entropy inequalities for the linear or Tsallis-2-entropy and monogamy relations.
Thereby we derive several new entropy inequalities for the linear entropy: First, we
present a dimension-dependent analogue to strong subadditivity. The existence of
such analogues is remarkable since the classic version of strong subadditivity is
known not to hold for the linear entropy [1]. As a byproduct we obtain a similar
relation in analogy to subadditivity. Moreover, we propose a yet unknown quadratic
entropy inequality that generalizes the pseudo-additivity [2] of Tsallis q-entropies
from separable to all states. This relation is shown to be stronger than subadditivity
in some cases.
Finally, we define a new measure of correlations and show that it follows a quasi-
ICQF-17 / 23
monogamy relation for systems of arbitrary dimension. Similarly to the case of
strong subadditivity, we find that although the classical Coffman-Kundu-Wootters
inequality is known not to generalize to higher dimensions, our dimension-
dependent correlation measure obeys an analogous inequality for arbitrary
dimensions.
[1] KMR. Audenaert, Journal of Mathematical Physics, (2017)
https://arxiv.org/pdf/0705.1276.pdf
[2] S. Abe, Physics Letters A, Volume 271, 74-79, (2000)
https://arxiv.org/pdf/cond-mat/0005538.pdf
Name Aravinda S
Affiliation IMSc Chennai, India
Title Combinatorial approach to nonclassicality and cryptographic security in single
systems
Abstract The concept of compatibility of two measurements in a generalized probability
theory is usually identified with their joint measurability. Here we provide a
geometric interpretation in terms of ―congruence‖, the requirement that the polytope
associated with the maximal knowledge states of a pair of measurements forms a
simplex. A natural division then arises between ―transitive theories‖, where
congruence is transitive, and ―intransitive theories‖, where the congruence is in
general not transitive. Transitive theories of single systems can reproduce
nonclassical features like no-cloning and measurement disturbance, but not
contextuality, for which the intransitive property is required. Here we indicate the
difference between these two theory types from a cryptographic perspective.
Additionally, we point out that in the context of single systems that the essence of
Spekkens’ toy model (2017) is that it is a transitive (albeit non-convex) theory.
Name Gautam Sharma Affiliation HRI, Allahabad, India Title Complementarity Relation for Coherence and Disturbance
Abstract Quantum measurements necessarily disturb the state of physical system. Once we
perform a complete measurement, the system undergoes decoherence and loses its
coherence. If there is no disturbance, the state retains all of its coherence. It is
therefore natural to ask if there is trade-off between disturbance caused to a state
and its coherence. We present a coherence disturbance complementarity relation
using the relative entropy of coherence. For bipartite states we prove a
complementarity relation between the quantum coherence, entanglement and
disturbance. Similar relation also holds for quantum coherence, quantum discord
and disturbance for a bipartite state. We illustrate the trade-off between the
coherence and the disturbance for single qubit state for various quantum channels.
ArXiv:1708.03090
Name Nitica Sakharwade Affiliation Perimeter Institute, Canada Title Bidirectional Dense Coding and Teleportation in Butterfly network
Abstract Non-local correlations via entangled states have been known to be resources for
two-party communication tasks such as teleportation and dense-coding. We are
interested in optimizing many such two-party communication tasks in a quantum
network of many parties akin to the role the internet played in classical
communication tasks. Specifically, we choose the simplest non-trivial
communication task of two communication tasks simultaneously achieved between
two-parties, Alice and Bob, and find optimal protocols for bidirectional
ICQF-17 / 24
teleportation and bidirectional dense coding by embedding them in the butterfly
network and using a classical network coding protocol. Surprisingly, we find that a
one-qubit channel (or two-cbit channel) along with pre-shared entanglement is
sufficient for bidirectional teleportation (or dense-coding). We also find a general
boundary rule that prescribes which parties require pre-shared entanglement for a
given set of two-party tasks on a quantum network. These results have implications
for post-quantum theories like the indefinite causal theories.
Name Ranjith Venkatrama Affiliation ALOPHIS group, Univ. of Cagliari, Italy Title Negations and Truth-Perspectives pertaining to Qudits based Multi-valued
Quantum Computational Logics
Abstract In the present work certain peculiar aspects of the concept of negation in quantum
computation are explored in the framework of a continuous t-norms based fuzzy-
type representation of qudit based quantum computational multivalued logics.
ICQF-17 / 25
Posters
Name Raunaq Ahmad Affiliation Bangalore University, India Title Statistical distinguishability of two unknown rotations using Majorana
geometric representation of N-qubit symmetric states
Abstract Ability to discriminate two unknown rotations (or equivalently, two
unitary operations ( )) with better precision is an important
foundational task as this is directly linked with aligning reference frames between
spatially separated parties sharing a quantum state. We address this issue by
making use of the Majorana geometric representation for pure permutationally
invariant multiqubit states. We show that when two unknown rotations are
applied on a pure symmetric N-qubit state , belonging to an N +1
dimensional irreducible unitary representation (R) of rotations, it is possible to
discriminate ( ) and
( ) perfectly,
when there are 2j = N distinct Majorana spinors constituting the quantum state.
We also discuss the possibility of discrimination of rotations using symmetric N
qubit states constituted by distinct Majorana spinors.
Name Balwant Singh Airy Affiliation GBPUAT, Uttarakhand, India Title Protecting entanglement by using weak measurement and quantum
measurement reversal against one and two sided amplitude damping channel
Abstract In this paper we have studied the effect of one and two sided amplitude damping
decoherence on the entanglement of Bell’s state by measuring their concurrence
and compare them. We found that in the case of two sided amplitude damping
state shows more protection of entanglement compare to the state
to amplitude damping. While in the case of one sided amplitude
damping both state perform equally. We found that in the case of two sided
amplitude damping after applying weak measurement and quantum measurement
reversal, state is protected more compare to the state
and similar results are obtained in the case of one sided amplitude
damping.
Name Natasha Awasthi
Affiliation GBPUAT, Pantnagar, India
Title Universal quantum uncertainty relations between non-ergodicity and loss of
information
Abstract We establish uncertainty relations between information loss in general open
quantum systems and the amount of non-ergodicity of the corresponding
dynamics. The relations hold for arbitrary quantum systems interacting with an
arbitrary quantum environment. The elements of the uncertainty relations are
quantified via distance measures on the space of quantum density matrices. The
relations hold for arbitrary distance measures satisfying a set of intuitively
satisfactory axioms. The relations show that as the non-ergodicity of the dynamics
increases, the lower bound on information loss decreases, which validates the
belief that non-ergodicity plays an important role in preserving information of
quantum states undergoing lossy evolution. We also consider a model of a central
qubit interacting with a fermionic thermal bath and derive its reduced dynamics, to
ICQF-17 / 26
subsequently investigate the information loss and non-ergodicity in such
dynamics. We comment on the ―minimal‖ situations that saturate the uncertainty
relations.
Name Shreya Banerjee Affiliation IISER, Kolkata, India Title The Minimum Distance of PPT Bound Entangled States from the Maximally
Mixed State
Abstract Using a geometric measure of entanglement quantification based on Euclidean
distance of the Hermitian matrices [1], we obtain the minimum distance between a
bipartite bound entangled nqudit density matrix and the maximally mixed state.
This minimum distance for which entangled density matrices necessarily have
positive partial transpose (PPT) is obtained as
√ √ ( )
, which is also a
lower limit for the existence of 1-distillable entangled states. The separable states
necessarily lie within a minimum distance of
from the Identity [1],where R
is the radius of the closed ball homeomorphic to the set of density matrices, which
is lesser than the limit for the limit for PPT bound entangled states. Furthermore
an alternate proof on the non-emptiness of the PPT bound entangled states have
also been given.
[1] Aryaman A Patel and Prasanta K Panigrahi. Geometric measure of
entanglement based on local measurement. arXiv preprint arXiv:1608.06145,
2016.
Name Kishor Bharti Affiliation NUS, Singapore Title Quantum Contextuality for Continuous Variables
Abstract We analyse n-cycle non-contextuality inequalities and discuss the condition for
the quantum violation for odd as well as even n-cycle. The set of quantum states
for qutrits, which can violate odd n-cycle noncontextuality inequality, shrinks as
we increase n. In the infinite n scenario, the only qutrit which violates the
inequality is the maximally contextual state. For even cycle, the necessary
condition for quantum violation depends on the difference of the two largest
eigenvalues for the density matrix ρ.
Name Samyadeb Bhattacharya Affiliation HRI, Allahabad, India Title Dynamics and thermodynamics of a central spin immersed in a spin bath
Abstract An exact reduced dynamical map along with its operator sum representation is
derived for a central spin interacting with a thermal spin environment. The
dynamics of central spin shows high sustainability of quantum traits like
coherence and entanglement in low temperature regime. However, for sufficiently
high temperature and when the number of bath particles approaches the
thermodynamics limit, this feature vanishes and the dynamics closely mimics the
Markovian evolution. The property of long time averaged state and the tapped
information of initial state for the central qubit are also investigated in detail,
confirming that the non-ergodicity of the dynamics can be attributed to the finite
temperature and finite size of bath. It is shown that if a certain stringent resonance
condition the long-time averaged state retains quantum coherence, which can have
far reaching technological implications in engineering quantum device. An exact
time local master equation of the canonical form is derived. With the help of this
master equation, the non-equilibrium properties of central spin system are studied
ICQF-17 / 27
by investigating the detailed balance condition and irreversible entropy production
rate. The result reveals the central qubit thermalizes only in limit of very high
temperature and large number of bath spins.
Name Suchetana Goswami Affiliation SNBNCBS, Kolkata, India Title Selftesting of any non-maximally entangled pure two-qubit state in
one-sided-device-independent scenario
Abstract The certification of quantum devices through the observation of quantum
nonlocality has implications for both quantum information and foundations of
quantum theory. Some extremal nonlocal quantum correlations of two-binary-
inputs-two-binary-outputs Bell scenario can be witnessed by the maximal
violation of a tilted Bell-CHSH inequality. These nonlocal correlations were
shown to selftest any pure two-qubit entangled state in a device-independent way.
Device-independent selftesting is a quantum information task in which one wishes
know the quantum state and measurements from the observed correlations without
any assumption on the dimension of the physical system. Recently, selftesting of
maximally entangled two-qubit state in a one-sided device-independent way (in
which one can do state tomography on one side and the other side is treated as
black-box device) was proposed. In this context, the maximal violation of a
steering inequality which certifies the maximally entangled state was shown to
selftest the maximal entanglement in a one-sided device independent way.
Selftesting via quantum steering was shown to provide certain advantage over
device-independent selftesting.
In this work, we consider the problem of selftesting of any pure nonmaximally
entangled two-qubit state through quantum steering. We note that in the two-
setting steering scenario, the maximal violation of a fine-grained steering
inequality can be used to witness certain extremal steerable correlations, which
certify all pure two-qubit nonmaximally entangled states. Motivated by this
observation, we are interested in selftesting of any pure nonmaximally entangled
state with these extremal steerable correlations. We demonstrate that by using the
fine-grained steering inequality and analog CHSH necessary and sufficient
condition of steerability, one can selftest any pure nonmaximally entangled two-
qubit state in a one-sided device-independent way.
Name Kamil Kostrzewa Affiliation University of Gdansk, Poland Title Investigating nonclassicality of many qutrits by symmetric two-qubit
operators
Abstract We introduce a method of investigating qutrit nonclassicality by translating qutrit
operators to symmetric two qubit operators. We show that this procedure sheds
light on the discrepancy between maximal qutrit entanglement and maximal
nonclassicality of qutrit correlations. Namely, we express Bell operators
corresponding to qutrit Bell inequalities in terms of symmetric two-qubit operators
and analyze the maximal quantum violation of a given Bell inequality from the
qubit perspective. As an example, we show that the two qutrit Collins-Gisin-
Linden-Massar-Popescu (CGLMP) Bell inequality can be seen as a combination
of Mermin's and Clauser-Horne-Shimony-Holt (CHSH) qubit Bell inequalities,
and therefore the optimal state violating this combination differs from the one
which corresponds to the maximally entangled state of two qutrits. In addition, we
discuss the same problem for a three-qutrit inequality. We also demonstrate that
the maximal quantum violation of the CGLMP inequality follows from
complementarity of correlations.
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Name C S Sudheer Kumar Affiliation IISER, Pune, India Title Violation of space-time Bell-CHSH inequality beyond Tsirelson bound via
postselection and quantum cryptography
Abstract Here we show that, if we insert context dependent unitary evolutions into spatial
(i.e., normal) Bell-CHSH test, then it is possible to violate space-time Bell-CHSH
inequality maximally (i.e., up to 4). Correct context dependency can be achieved
via postselection. However this does not contradict Tsirelson quantum bound √ ,
because the latter has been derived without taking into consideration context
dependent unitary evolutions and/or postselection. As an important application,
this leads to a more efficient (in terms of resource (singlets) and classical
communication required) and more sensitive (to eavesdropping) quantum key
distribution protocol, compared to Ekert and Wigner QKD protocols.
Name Som Kanjilal Affiliation Bose Institute, Kolkata, India Title Quantifier of effective Resource State in Remote State Preparation
Abstract The nature and effectiveness of the resource determining the efficiency of a
quantum information task is crucial to our understanding of the protocol itself. In
an earlier work [2], it was shown that quantum discord is a legitimate resource for
remote state preparation - it was shown that fidelity achieved using the RSP
protocol they formulated was the same as the value of geometric discord for the
shared resource state. Using a newly suggested scheme for remote state
preparation of pure quantum qubit state (that will be briefly reviewed in this
poster), it has been argued that discord is not always a faithful resource as one can
achieve finite fidelity for even zero discord states. As an alternative to quantum
discord as an effective resource for such a scheme, we suggest here the use of the
simultaneous correlations that exist in two (C2) and three (C3) mutually unbiased
bases [1] as resources for the said RSP scheme. We show that both the quantities
C2 and C3 are monotonic functions of fidelity for classes of zero discord Bell-
diagonal states. On the other hand, for any general Bell diagonal state (that
includes both zero and non-zero discord states), we demonstrate that in addition to
the monotonocity of the dependence of C3 on fidelity, there is also an explicit
functional relationship between it and RSP fidelity. These results, we argue,
justify arguing for the use of measures of quantum correlations beyond discord for
quantifying the efficiency of such RSP schemes.
[1] Guo, Yu and Wu, Shengjun Sci. Rep. 1, 7179 (2014).
[2] B Dakic et al.,Nature Physics 8, 666670 (2012).
Name Swati Kumari Affiliation NIT, Patna, India Title Inequivalent Leggett-Garg Inequalities Abstract Fine [1] showed that for two parties, two inputs and two outputs only relevant
inequality is the CHSH one. In recent times, there is an upsurge of interest for
studying the issue of macrorealism and Leggett-Garg inequalities (LGIs). Various
formulations of LGIs have recently been proposed, for example, Wigner form of
LGIs (WLGIs), Clauser-Horne form of LGIs (CHLGIs). Standard Leggett-Garg
Inequalities (SLGIs) are often considered to be the temporal analogue of CHSH
Inequalities. In contrast to the CHSH scenario, here we show that for three and
ICQF-17 / 29
four-time measurement scenario, WLGIs and CHLGIs are inequivalent, and both
of them are stronger than SLGIs.
[1] A. Fine, Phys. Rev. Lett. 48, 291(1982).
Name Avijit Misra Affiliation IMSc Chennai, India Title Complementarity between tripartite quantum correlation and bipartite Bell-
inequality violation in three-qubit states
Abstract We find a single parameter family of genuinely entangled three-qubit pure states,
called the maximally Bell-inequality violating states (MBV), which exhibit
maximum Bell-inequality violation by the reduced bipartite system for a fixed
amount of genuine tripartite entanglement quantified by the so-called tangle
measure. This in turn implies that there holds a complementary relation between
the Bell-inequality violation by the reduced bipartite systems and the tangle
present in the three-qubit states, not necessarily pure. The MBV states also exhibit
maximum Bell-inequality violation by the reduced bipartite systems of the three-
qubit pure states with a fixed amount of genuine tripartite correlation quantified by
the generalized geometric measure, a genuine entanglement measure of multiparty
pure states, and the discord monogamy score, a multipartite quantum correlation
measure from information-theoretic paradigm. The aforementioned
complementary relation has also been established for three-qubit pure states for
the generalized geometric measure and the discord monogamy score, respectively.
The complementarity between the Bell-inequality violation by the reduced
bipartite systems and the genuine tripartite correlation suggests that the Bell-
inequality violation total tripartite correlation present in the entire system. in the
reduced two-qubit system comes at the cost of the total tripartite correlation
present in the entire system.
Name Shiladitya Mal Affiliation SNBNCBS, Kolkata, India Title Scheme for implementing dichotomic quantum measurements through non-
ideal Stern Gerlach setup
Abstract Positive operator valued measures (POVMs) are the most general class of
quantum measurements. There has been significant interest in the theory and
possible implementations of generalized measurement in the form of POVMs.
Such measurements are useful in the context of cryptography, state discrimination,
preparation of arbitrary states and for monitoring quantum dynamics. As argued
by P. Busch (Phys. Rev. D 33 (1986) 2253), the most general dichotomic POVMs
are characterised by two real parameters known as sharpness and biasedness of
measurements. While unbiased unsharp measurements have been demonstrated
experimentally, for example using the quantum feedback stabilization of number
of photons in a microwave cavity (Nature (London) 477, 73 (2011)), as well as in
the context of energy measurements of trapped ions, however, to the best of our
knowledge unsharp biased measurements has not yet been probed experimentally.
For this purpose, we propose in this work, an empirically realizable scheme using
non-ideal SG setup. The relevant formulation involves identifying one to one
correspondence between biasedness, unsharpness of measurements and the key
parameters characterising non-ideal SG setup. This study has the potentiality to be
useful for the implementations of various quantum information tasks as well as
experiments related to quantum foundational studies based on POVMs.
ICQF-17 / 30
Name Chiranjib Mukhopadhyay Affiliation HRI, Allahabad, India Title Quantum speed limit constraints on a nanoscale autonomous refrigerator
Abstract Quantum thermal machines have attracted renewed attention in last few years. We
propose a figure of merit for a model of quantum absorption refrigerator
considering the constraints on the speed of evolution. We show that this quantity,
hence termed the bounding second order cooling rate (BSOCR), is linearly
proportional to the strength of biasing interaction. We derive a bound on
efficiency at maximum value of this figure of merit in the high temperature limit.
We also study how the quantum zeno effect affects the BSOCR. We compare this
approach with another approach based on known a priori probability distributions
over steady state performance parameters, which itself is investigated here for the
first time for absorption refrigerators, and point out the similarity in the results
furnished by both approaches.
Name Sumit Nandi Affiliation IOP, Bhubaneswar, India Title Co-operative communication protocols
Abstract Quantum entanglement plays an important role in various communication
protocols, like teleportation, secret sharing, superdense coding, and quantum key
distribution. We consider the scenario when more than two parties are involved in
the protocol. One party wishes to communicate information with the help of other
parties. The information could be classical, a quantum state
or establishment of a secret key. A multipartite entangled state is shared between
many parties. Various parties make measurement or apply unitary transformations,
to allow sender, Alice, to communicate with receiver, Bob. We consider secret
sharing and Quantum key distribution to find conditions that a resource state must
satisfy for the protocol to work exactly.
Name Suma S P Affiliation University of Mysore, India Title Study on a class two qubit symmetric separable states in term of moments of
angular momentum operators.
Abstract We express PPT criterion for a system of 2-qubit symmetric states in terms of the
well-known Fano Statistical tensor parameters and prove that a large set of
separable symmetric states are characterized by real statistical tensor parameters
only. The physical importance of these states are brought out by employing the
trivariate representation of density matrix wherein the components of J namely Jx,
Jy, Jz are considered to be the three variates. We prove that this set of separable
states is characterized by the vanishing average expectation value of Jy and its
covariance with Jx and Jz.
Name Varad Pande Affiliation HRI, Allahabad, India Title Quantum Information Transfer Using Weak Measurements and Any Non-
product Resource State
Abstract Information about an unknown quantum state can be encoded in weak values of
projectors belonging to a complete eigenbasis. We present a protocol that enables
one party -- Bob -- to remotely determine the weak values corresponding to weak
measurements performed by another spatially separated party -- Alice. The
particular set of weak values contains complete information of the quantum state
encoded on Alice's ancilla, which enacts the role of the preselected system state in
ICQF-17 / 31
the aforementioned weak measurement. Consequently, Bob can determine the
quantum state from these weak values, which can also be termed as remote state
determination or remote state tomography. A combination of non-product bipartite
resource state shared between the two parties and classical communication
between them is necessary to bring this statistical scheme to fruition.
Significantly, the information transfer of a pure quantum state of any known
dimensions can be affected even with a resource state of low dimensionality and
purity with a single measurement setting at Bob's end.
Name Md Qutubuddin Affiliation NIT, Patna, India Title Improved quantum violation of macrorealist and noncontextual inequalities
Abstract In a recent paper [1] it is shown that for a qutrit system the maximum quantum
violation of three-time Leggett-Garg inequalities (LGIs) can exceed the L ̈der
bound if von Neumann collapse rule is invoked. Even, the violation can approach
to the algebraic maximum in the asymptotic limit of system size. We show that for
the case of qutrit system the quantum violation can be further improved by
suitably choosing the intermediate unitary evolutions between two measurements.
We then pointed out that the choice of basis for invoking the von Neumann
projective rule is not unique for a degenerate observable. We found that choice of
basis can improve the maximum quantum violation of LGIs. We further show that
the simplest non-contextual inequalities (NCIs) can also violated if von Neumann
rule is used as opposed the recent claim [1]. We provide a discussion about the
experimental verifiability of our results using optical setup.
[1] C. Budroni and E. Emary, [Phys.Rev.Lett.113, 050401 (2014)].
Name Arun Sehrawat Affiliation IISER Mohali, Punjab, India Title Quantum constraints stronger than uncertainty relations
Abstract Every statistical operator—that represents a quantum state—must follow the three
conditions Hermiticity, normalization, and positivity. These conditions give birth
to quantum constraints on the expectation values with the aid of Born’s rule,
which connects the mean values for any set of operators to a quantum state. The
quantum constraints specify a permissible region of the expectation values. For a
set of observables, the allowed region is a compact and convex set in a real space,
and all its extreme points come from pure quantum states. By defining an
appropriate concave function on the permitted region and then finding its absolute
minimum at the extreme points, one can establish a tight uncertainty relation. The
permissible region resides in every other region bounded by an uncertainty
relation. A point outside the admissible region—even if it satisfies a tight
uncertainty relation—does not correspond to any quantum state. In that sense, the
quantum constraints are optimal.
Name Ritabrata Sengupta Affiliation IISER, Berhampur, Odisha, India Title Extendability and complete extendability of states in Fock space
Abstract Motivated by the notion of k-extendability and complete extendability of the state
of finite level quantum system as described by Dorherty et al (Phys Rev A
69:022308), we introduce parallel definition in the context of Gaussian state using
only the properties of covariance matrices derive necessary and sufficient
ICQF-17 / 32
condition for their complete extendability. It turns out that the complete
extendability property is equivalent to separability property of bipartite Gaussian
state.
Following the proof of quantum de Finetti theorem as outlined in Hudson and
Moody (Z. Wahrscheinlichkeitstheorie und Verw. Gebiete 33(4):343-351), we
showed that separability is equivalent to complete extendability for a state in a
bipartite Hilbert space where at least one of which is of dimension greater than 2.
This, in particular, extends the result of Fannes, Lawis, Verbeure (Latt. Math.
Phys. 15(3): 155-260) to the case of an infinite dimensional Hilbert space whose
algebra of all bounded operators is not separable.
Name Ashutosh Singh Affiliation RRI, Bangalore, India Title Manipulation of entanglement sudden death in an all-optical experimental
setup
Abstract The unavoidable and irreversible interaction between an entangled quantum
system and its environment causes decoherence of the individual qubits as well as
degradation of the entanglement between them. Entanglement sudden death (ESD)
is the phenomenon wherein disentanglement happens in finite time even when
individual qubits decohere only asymptotically in time due to noise. Prolonging
the entanglement is essential for the practical realization of entanglement-based
quantum information and computation protocols. For this purpose, the local NOT
operation in the computational basis on one or both qubits has been proposed. In
this talk, I will discuss the phenomenon of ESD followed by an all-optical
implementation of the NOT operations that can hasten, delay, or completely avert
ESD, all depending on when it is applied during the process of decoherence for
the polarization entangled photonic qubits as the system [1]. The simulation
results of such manipulations of ESD will be presented along with the latest
experimental results.
[1] M. P. Almeida, F. de Melo, M. Hor-Meyll, A. Salles, S.P. Walborn, P. H.
Souto Ribeiro, L. Davidovich, Science 316, 555 (2007).
Name Souradeep Sasmal Affiliation Bose Institute, Kolkata, India Title Necessary and sufficient condition for violation of a steering inequality for
two-qubit states, monogamy and shareability of steering
Abstract Necessary and sufficient condition for violation of Clauser-Horne-Shimony-Holt
like inequality for steering by an arbitrary two qubit state is derived. As a
corollary of this derivation maximal violation of this inequality is obtained. Then
we establish monogamy relation for this steering inequality which states that two
party can’t steer a third party’s system simultaneously through violation of this
inequality. Then we investigate how two observers can demonstrate steering of
third party’s system invoking a scenario where half of an entangled pair shared
between single Alice in one wing and several Bobs on the other wing.
Interestingly we also show three Bobs can steer Alice’s system considering three
settings steering inequality and conjecture when steering is probed through n-
settings steering inequality atmost n Bobs can demonstrate steering of Alice’s
system.
ICQF-17 / 33
Name H. S. Smitha Affiliation University of Mysore, India Title Construction of new observables for spin-1 system and their optimum
measurement
Abstract Any spin-j density matrix is completely characterized by independent
parameters, where . The optimum measurement to obtain all the
independent parameters involves Mutually Unbiased Bases. For spin-1/2 system,
the eigenbasis of Pauli operators turn out to be the MUBs. In the Stern-Gerlach
experiment, all the parameters , and characterizing the spin-1/2 density
matrix are obtained when the measurement is carried out in the diagonal bases of
Pauli operators and the physical interpretation is very clear. To achieve the same
for spin-1 system, with the help of existing MUBs, we first obtain the set of eight
parameters characterizing the density matrix in the Weyl basis. As these
parameters do not have any physical interpretation, we construct a new set of
operators, using the suitable combination of projection operators required to
obtain all the eight parameters. These operators form an orthonormal operator
basis. The new coefficients which are the expectation values of the these operators
now have the physical meaning. In an experiment, measurement for spin-1 system
thus corresponds to the measurement of particular combination of different order
moments of , and .
Name Akhilesh K. S Affiliation University of Mysore, India Title Geometric phase, spin squeezing and Majorana star constellation in pure
symmetric states
Abstract Berry phase plays a foundational role in understanding geometry of quantum
systems. For an arbitrary pure qubit state, Berry phase admits a geometric
representation on the surface of the unit Bloch sphere. As Majorana construction
(E. Majorana, Nuovo Cimento 9, 43 (1932)) enablesnmapping of permutationally
invariant N –qubit pure states with N unit vectors on the surface of the Bloch
sphere, it offers a powerful method to explore Berry phase associated with
multiqubit systems geometrically. To this end, we focus on the Berry phase of
pure symmetric N -qubit states constructed using only two distinct Majorana
spinors. This brings forth the connection between Berry phase, entanglement and
spin squeezing in this specific class of N -qubit symmetric states.
Name Shreekanth S Affiliation Regional Institute of Education, Mysore Title Quantum Fisher Information Matrix for mixed spin-1/2 system.
Abstract Employing the new parametrization of spin-j density matrix we outline the
procedure to compute Quantum Fisher Information Matrix which plays a key role
in parameter estimation. Taking the example of mixed spin-1/2 density matrix we
show that the off diagonal elements of the Fisher Information Matrix are
proportional to the covariance of spin operators σx, σy and σz .
ICQF-17 / 34
Note