superconducting quantum computing · 2019-06-11 · summary we designed and fabricated several...
Post on 13-Jun-2020
5 Views
Preview:
TRANSCRIPT
Superconducting Quantum ComputingXiaobo Zhu
CAS Center for Excellence in Quantum Information and Quantum Physics
University of Science and Technology of China
ITU Workshop on Quantum Information Technology (QIT) for Networks
Shanghai, China, 5th June 2019
Email: xbzhu16@ustc.edu.cn
How to scale up?
Ultra-high precision analog circuit
• Better pulse calibration
• Less crosstalk
• Less state leakage
• Higher readout efficiency
• Less TLS
• Deeper connectivity
……
More qubits and longer depth
Sample Fabrication
To stabilize the sample parameters
To speed up the development of new samples
Qubit Samples
Longer
Coherent time
3 Bits 5 Bits 6 Bits 9 Bits 10 Bits 12 Bits 24 Bits
T1: ~40usT1: ~5us T1: ~15us
More
Qubits
Ultra-low noise and temperature platform
~100 Coaxial cables
>99.9% voltage resolution
Sample rate>1GHz
Bandwidth :0-20GHz
~100 DA Chanel
< 20mK
~10ppm(1h) DC bias
Multi-qubit control
▪High-precision controlling of amplitude, phase and time sequence▪Compensation of the crosstalk and calibration of the wave deformation▪Arbitrary multi-channel quantum circuit
Quantum operating System
12-Qubit sample characterizations
Summary of T1 and T2
q1 q2 q3 q4 q5 q6 q7 q8 q9 q10 q11 q12
T1(us) 40.1 34.7 30.8 40.4 31.8 34.3 46.5 38.1 32.2 54.6 29.6 30.3
T2(us) 7.9 1.5 6.3 2.4 4.9 2.7 6.8 2.3 5.1 3.5 5.9 3
f01
(GHz)4.978 4.183 5.192 4.352 5.11 4.226 5.03 4.3 5.142 4.14 4.996 4.26
f_ah
(MHz)-247.7 -203.5 -245.7 -202.7 -246.9 -201.5 -245.8 -203 -243.5 -203.4 -246.4 -201.4
T1 ~ 30us-50us
T2* > 20us at optimal point
Q7 at optimal point Q7 at optimal point
Q7 at optimal point
Q7 at optimal point
Single − qubit gate𝑠 fidelity>99.9%(by randomized benchmarking)
The fidelity of single-qubit gates operation
Nonadiabatic CZ gate
Theoretic simulation
PRL,115, 190801 (2015).
PRX, 8, 021059 (2018).
Leakage from Eigenstate
F>99.97%(After 12 hours
differential evolution (DE)
searching.)
1.06Ts (34ns)for infinite
bandwidth, Ts=1/(2g11,02)
1.17Ts for 300MHz bandwidth
(After 1 hour Nelder Mead (NM)
algorithm searching.)
Experimental results:optimization by RB
The fidelity of CZ gates operation
CZ ~99.54%, After 4 hour NM algorithm searching
12-Qubit Linear Cluster state
Ts =1/(2g11,20)~32ns
g11,20=15.6MHz
Tgate=40ns~1.25Ts
~32ns
CCZ gate
CCZ gate fidelity
F=93.3%(experiment),78.5ns and F=99.3%(numeric)
Conclusion of nonadiabatic way
“Realization of high-fidelity nonadiabatic CZ gates
with superconducting qubits”, submitted
Leakage error in our nonadiabatic CZ gates
is not a major challenge
This scheme is suitable for the design of
CCZ gates ,but a new RB method is needed
NM is sensitivity to initial points
12-Qubit entanglement
Genuine multipartite entanglement (GME)
• Cannot be expressed as a bi-separable state or a mixture of bi-separable states
• Benchmark for the quality of quantum processor
• Greenberger-Horne-Zeilinger (GHZ) state: 𝐺𝐻𝑍N = ( 0 ⊗𝑁 + 1 ⊗𝑁)/ 2
14-qubit GHZ in ion trap
10-qubit GHZ in superconducting
quantum circuit 18-qubit GHZ with six photons
Phys. Rev. Lett. 106, 130506 (2011) Phys. Rev. Lett. 119, 180511 (2017) Phys. Rev. Lett. 120, 260502 (2018)
…
12-Qubit Linear Cluster state
Gate sequence
12-Qubit Linear Cluster state
Parallel optimization of CZ gates
12-Qubit Linear Cluster state
Gate fidelity
State preparation error
Readout error
Triple the length, more ZZ coupling
12-Qubit Linear Cluster state
*Phys. Rev. Lett. 94,
060501 (2005)
Phys. Rep. 474, 1
(2009)
Only two local measurement settings*
12-Qubit Linear Cluster state
LC state fidelity
Over 55% for 12-qubit LC state,
21 statistical standard deviations
above 50%
250,000 projective measurements
12-Qubit Linear Cluster state
12-Qubit Linear Cluster state
0.707(8)
12 − qubit linear cluster state created by single-qubit gates and CZ gates. The fidelity is 70.7±0.8%.
Phys. Rev. Lett.
122, 110501 (2019).
12-Qubit Linear Cluster state
8 CZ-gate layers to generate a 2D cluster state Always 3 layers
Strongly correlated quantum walks with a
12-qubit superconducting processor
1D chain quantum walk
One photon Two photons
Pulse sequence
One photon Two photons
1D chain quantum walk
One photon Two photonsZ. Yan et al., Science
10.1126/science.aaw1611 (2019).
10-Qubit Entanglement with a
Superconducting Circuit
10-Qubits processor with complete connection
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
CenterResonantor
GHZ state preparation
Full state tomography
10-bit GHZ state fidelity
is about 66%
PRL 119, 180511 (2017)SQ:arXiv:1905.00320, Ion trap:arXiv:1905.0572
2014
First transmon/Xmon
qubit T1~5μs,
T2*~2μs
Improve the coherence time
T1~15μs, T2*~ 10μs.
2015
4-Qubits processor
HHL algorithm demonstration
PRL 118, 210504 (2017)
2016 2018
2018
50-Qubits
PRL 119,180511(2017)
10-qubits entanglement
quantum Cloud
24-Qubits processor
12-engtanglement
PRL 122, 110501 (2019)
2020
Quantum
Supremacy
??
2015 2017
Summary
We designed and fabricated several versions of quantum
processor, on which integrated up to 24 quibts
The typical T1 and T2 time are both longer than 20 micro-
seconds
The single-bit gate fidelity is >99.9%, for the CZ gate it
reaches 99.5% in the best case, and for CCZ is ~93.3%
We generate a 10-qubit GHZ state with a fidelity of 0.668 ±0.025, further obtained a 12-qubit LC state with 0.707 ±0.008
We demonstrated Strongly correlated quantum walks with a
12-qubit superconducting processor
Experiments:Institute of Physics, Chinese Academy of Sciences, Beijing, China
Zhejiang University,Zhejiang,China
Micro-fabrication: The micro-fabrication lab on IOP-China, National Center for Nanoscience and Technology and USTC.
Theories:IOP-CAS, Beijing, China
Zhejiang University, Zhejiang, China
Nanjing University, Nanjing, China
Fuzhou University, Fuzhou, Fujian,China
Tsinghua University, Beijing, China
Beijing Computational Science Research Center
Hangzhou Normal University
University of Kansas, USA
Institute of Automation, Chinese Academy of Sciences
NTT Basic Research Laboratories, Atsugi, Japan
National Institute of Informatics,Tokyo, Japan
RIKEN, Japan
Acknowledgements
The project is supported by the
Chinese Academy of Science,
National Nature Science Foundation
of China, National Basic Research
Program, Alibaba Cloud, Science and
Technology Committee of Shanghai
Municipality, and Anhui Province.
Thank you for your attention!
4 bits HHL algorithm
4 qubits HHL algorithm
4 qubits HHL algorithm
4 qubits HHL algorithm
PRL 118.2105
04 (2017)
Quantum Switch by
Longitudinal Control Field
The principle of the switch
Qubit-Resonance
Qubit-Qubit
Avoid crossing and decoupling
Switching on/off the coherent oscillation
Switching on/off the coherent oscillation
“An efficient and compact quantum switch for quantum circuits”,
npj Quantum Information, 4:50, (2018).
top related