Adaptive optical phase estimation using time-symmetric quantum smoothing

T. A. Wheatley*, D. W. Berry, H. Yonezawa, D. Nakane, H. Arao, D. T. Pope, T. C. Ralph, H. M. Wiseman, A. Furusawa, E. H. Huntington

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review


We present an experimental demonstration of quantum smoothing, a non causal version of quantum parameter estimation that has applications from gravitational wave detection to quantum key distribution. An existing technique for this type of parameter estimation is quantum filtering, which uses past observations only. The technique presented here is time-symmetric that uses past and future observations to obtain a more precise estimate. We couple this innovative estimation technique with an adaptive detection scheme to demonstrate an estimation of the optical phase of light measured to be 2.24 ± 0.14 times better than the standard quantum limit. This approaches our theoretically derived prediction of a mean square error improvement of 2√2 times over the standard quantum limit [1].

Original languageEnglish
Title of host publicationQCMC 2010 : Quantum Communication, Measurement and Computing
Subtitle of host publicationthe Tenth International Conference
EditorsTimothy Ralph, Ping Koy Lam
Place of PublicationCollege Park, MD
PublisherAmerican Institute of Physics
Number of pages4
ISBN (Print)9780735409217
Publication statusPublished - 2011
Externally publishedYes
Event10th International Conference on Quantum Communication, Measurement And Computing, QCMC 2010 - Brisbane, QLD, Australia
Duration: 19 Jul 201023 Jul 2010

Publication series

NameAIP conference proceedings


Other10th International Conference on Quantum Communication, Measurement And Computing, QCMC 2010
CityBrisbane, QLD


  • adaptive
  • parameter estimation
  • quantum optics
  • smoothing


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