Prsentation PowerPoint

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www.lac.u-psud.fr
Universal Coherence Loss Protection by the
Quantum Zeno Effect
V. Akulin1, E. Brion1, D. Comparat1, I. Dumer2,
G. Harel3, N. Kébaïli1, G. Kurizki4, I.
Mazets4,5, P. Pillet1,
1Laboratoire Aimé Cotton, CNRS II, Bât. 505,
91405 Orsay
2College of Engineering, University of
California, Riverside, CA 92521, USA
3Departement of Computing, University of
Bradford, Bradford BD7 1DP, UK
4 Department of Chemical Physics,
Weizmann Institute of Science, 76100 Rehovot,
Israel 5A.F. Ioffe Physico-Technical
Institute, 194021 St. Petersburg, Russia.
Les Houches April 26th 2004
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Quantum Information and Quantum Errors
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Outline
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The Quantum Zeno Effect
B. Misra and E.C.G. Sudarshan, J. Math. Phys. 18,
756 (1977)
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Coherence Protection in compound systems
trivial case
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Coherence Protection in compound systems
general case
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Coherence Protection in compound systems
general case
Coding matrix ? j0? ? C0, ? k, ?j0C-1EkCj0?
0 Necessary condition M ? A 1.
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Application to a physical system
78Rb
level s L 0 A
1 ( no ancilla )
M 6 errors considered (3 magnetic, 3 electric)
? A ? M1 7 (L3)
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Ancilla adding through pumping
J5/2
J7/2
-5/2
1/2
3/2
5/2
-7/2
-5/2
-3/2
-1/2
1/2
3/2
5/2
7/2
60f
-1/2
-3/2
5d
-3/2
-1/2
1/2
3/2
?1
J3/2
?1 ?2
5p
-3/2
-1/2
1/2
3/2
J3/2
5s
-1/2
1/2
J1/2
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Coding through the non-holonomic control
C0
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Action of infinitesimal errors
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Decoding through the non-holonomic control
y(t)?
dy?
C
y0?
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Projection through spontaneous emission
j(t)?
dj?
C0
j0?
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Conclusion
A physical method has been proposed to protect
coherence against unitary action of the
environment
Generalize to arbitrary (non-unitary errors),
adaptation of our algorithms
Find another more  practical  system