Quantum Information Processing

, Volume 6, Issue 6, pp 431–444

Signatures of Incoherence in a Quantum Information Processor

  • Michael K. Henry
  • Alexey V. Gorshkov
  • Yaakov S. Weinstein
  • Paola Cappellaro
  • Joseph Emerson
  • Nicolas Boulant
  • Jonathan S. Hodges
  • Chandrasekhar Ramanathan
  • Timothy F. Havel
  • Rudy Martinez
  • David G. Cory
Article

DOI: 10.1007/s11128-007-0063-4

Cite this article as:
Henry, M.K., Gorshkov, A.V., Weinstein, Y.S. et al. Quantum Inf Process (2007) 6: 431. doi:10.1007/s11128-007-0063-4

Incoherent noise is manifest in measurements of expectation values when the underlying ensemble evolves under a classical distribution of unitary processes. While many incoherent processes appear decoherent, there are important differences. The distribution functions underlying incoherent processes are either static or slowly varying with respect to control operations and so the errors introduced by these distributions are refocusable. The observation and control of incoherence in small Hilbert spaces is well known. Here we explore incoherence during an entangling operation, such as is relevant in quantum information processing. As expected, it is more difficult to separate incoherence and decoherence over such processes. However, by studying the fidelity decay under a cyclic entangling map we are able to identify distinctive experimental signatures of incoherence. This is demonstrated both through numerical simulations and experimentally in a three qubit nuclear magnetic resonance implementation.

Keywords

decoherence incoherence open quantum system fidelity decay quantum error correction 

PACS

03·65·yz 03·67-a 03.67·Ac 03·67·Pp 

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Michael K. Henry
    • 1
  • Alexey V. Gorshkov
    • 2
  • Yaakov S. Weinstein
    • 3
  • Paola Cappellaro
    • 1
    • 2
    • 6
  • Joseph Emerson
    • 4
  • Nicolas Boulant
    • 1
  • Jonathan S. Hodges
    • 1
  • Chandrasekhar Ramanathan
    • 1
  • Timothy F. Havel
    • 1
  • Rudy Martinez
    • 5
  • David G. Cory
    • 1
  1. 1.Department of Nuclear Science and EngineeringMassachusetts Institute of TechnologyCambridgeUSA
  2. 2.Physics DepartmentHarvard UniversityCambridgeUSA
  3. 3.Quantum Information Science GroupThe Mitre CorporationEatontownUSA
  4. 4.Department of Applied Mathematics and Institute for Quantum ComputingUniversity of WaterlooWaterlooCanada
  5. 5.Department of Natural SciencesNew Mexico Highlands UniversityLas VegasUSA
  6. 6.ITAMP, Harvard-Smithsonian Center for AstrophysicsCambridgeUSA

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