Power and strangeness of the quantum
Quantum theory has opened to us the microscopic world of particles, atoms and photons…
….and has given us the keys of modern technologies
This is a theory whose logics challenges our classical intuition, even if its strangeness remains generally veiled at the
macroscopic level
Recent experiments lead us to believe that the microscopic strangeness of quantum physics could be harnessed to realize new tools for communicating, computing or measuring things
better…
Moore’s law: every 18 months computer power doubles
faster = smaller
Pentium 4 (2002)
1 atom
ENIAC (1947)
from: Gordon E. Moore “No exponential is forever…“
Progress in technology …
Light is a wave and an ensemble of photons (Einstein 1905)
Atoms are particles and matter waves (de Broglie, 1923)
Quantum physics is based on the wave-particle duality and the superposition
principle
Quantum physics and the superposition principle…
x y
|>=|X> + |Y>
Superposition of positions…
+
…or superposition of atomic states of
different energies …
Environment
or
Decoherence
The environment «spies » on quantum systems and destroys their quantum coherence very efficiently
How thoughts experiments controlling a « zoo of particles » have become real
New quantum technologies:
Tuneable Lasers
Fast computers
Supraconducting materials
Why is it important to be able to manipulate single quantum particles?
Curiosity: is it possible? How does Nature behaves at this level?
Small systems reacts faster and pack more information per unit volume, leading to more powerful devices (Moore’s law)
We never experiments with single electrons, atoms or small molecules…In thought experiments we assume that we do. It always results in ridiculous consequences… » (Schrödinger 1952)
Quantum physics makes a wide range of new states accessible for possible applications
More powerful computers and/or simulators
(quantum logic)
More secrete communications
(quantum cryptography)
More precise measurements
(quantum metrology)
1960 1970 1980 1990 2000 2010 2020 year
1 atom per bit num
ber
of ato
ms p
er
bit
~ 2017
faster = smaller
How many atoms per bit?
Pentium 4 (2002)
1 atom
ENIAC (1947)
1019
1015
1011
107
103
100
Pentium 4
R. W. Keyes, IBM J. R&D 32, 26 (1988)
Progress in technology …
22 nm transistor
A computer in a Schrödinger cat state to break the RSA code?
Quantum computers would exploit state superpositions and entanglement in ensemble of real or artificial atoms to compute more efficiently
Decoherence is the big challenge.
Ways to correct for it
are investigated.
Proof of principle
experiments under way with small
ensembles of atoms
1,E-18
1,E-17
1,E-16
1,E-15
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
1,E-06
1,E-05
1,E-04
1,E-03
1,E-02
1,E-01
1,E+00
1,E-06 1,E-03 1,E+00 1,E+03 1,E+06 1,E+09 1,E+12 1,E+15
Frequency [Hz]
Another illustration of the law “smaller is faster and better”: Clock speed and accuracy vs time
Fractional accuracy at one day
Sundial Period = 1 day
Accuracy ≈ 1-10 minutes
Pendulum Period ≈ 1 s
Accuracy ≈ 10 ms
Quartz Period ≈ 100 ns Accuracy ≈ 10-10
Cesium fountain Period ≈ 108 ps
Accuracy ≈ 3x10-16 Al+ optical Period ≈ 1 fs
Accuracy ≈ 8.6x10-18
10-6 10-3 100 103 106 109 1012 1015
10-3
10-6
10-9
10-12
10-15
10-18
1
Towards 10-18
accuracy?
27Al+ vs. 27Al+
C.-W. Chou, et al.
PRL 104, 070802 (2010)
Comparing two single ion clocks (David Wineland group at NIST)
General relativity test: clocks 33 cm apart in gravitational fields tick at different rates!
Measured:
Expected: (33 cm)
(37 +/- 15 cm)
33
cm
C. W. Chou, et al.
Science 329, 1630 (2010)
Practical applications for clocks keeping time within a handful of seconds in the age of
the Universe?
Better GPS able to track very small motions (at millimeter scale?)
Geodesic surveys (oil prospection?)
Earthquakes warnings?
Unpredictability of blue sky research
Laser (1960)
Highly transparent
optical fibers
(1970’s)
Transistors and Integrated circuits (1949 - 1990’s)
Global communication
network
Towards a quantum internet?
Magnetic resonance imaging (MRI)
Magnetic resonance
(1946)
+
Superconducting magnets (1970’s)
+
Fast small Computers (1970’s)