### Abstract

Summary form only given. Interferometry is the basis of many high-precision measurements. The ultimate limit to the precision is due to quantum effects. This limit is most easily explored for a Mach-Zehnder interferometer The outputs of this device can be measured to yield an estimate φ of the phase difference φ between the two arms of the interferometer. It is well known that this can achieve the standard quantum limit for phase variance when an N-photon number state enters one input port. Several authors have proposed ways of reducing the phase variance to the Heisenberg limit. In this paper we show that there is a physical measurement scheme using photodetectors and feedback that is almost as good as the optimal measurement. The fundamental idea is that, in addition to the unknown phase we wish to measure, φ, in one arm of the interferometer, we introduce a known phase shift, Φ, into the other arm of the interferometer. After each photodetection we adjust this introduced phase shift in order to minimize the expected uncertainty of our best phase estimate φ after the next photodetection. This feedback process is uniquely defined using Bayesian statistics, and can be solved exactly for moderate photon numbers.

Language | English |
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Title of host publication | Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001 |

Place of Publication | Piscataway, N.J. |

Publisher | Institute of Electrical and Electronics Engineers (IEEE) |

Pages | 60-61 |

Number of pages | 2 |

ISBN (Electronic) | 155752663X, 9781557526632 |

DOIs | |

Publication status | Published - May 2001 |

Externally published | Yes |

Event | Quantum Electronics and Laser Science Conference, QELS 2001 - Baltimore, United States Duration: 6 May 2001 → 11 May 2001 |

### Other

Other | Quantum Electronics and Laser Science Conference, QELS 2001 |
---|---|

Country | United States |

City | Baltimore |

Period | 6/05/01 → 11/05/01 |

### Fingerprint

### Cite this

*Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001*(pp. 60-61). [961853] Piscataway, N.J.: Institute of Electrical and Electronics Engineers (IEEE). https://doi.org/10.1109/QELS.2001.961853

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*Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001.*, 961853, Institute of Electrical and Electronics Engineers (IEEE), Piscataway, N.J., pp. 60-61, Quantum Electronics and Laser Science Conference, QELS 2001, Baltimore, United States, 6/05/01. https://doi.org/10.1109/QELS.2001.961853

**Adaptive measurements and optimal states for quantum interferometry.** / Berry, D. W.; Wiseman, H. M.

Research output: Chapter in Book/Report/Conference proceeding › Conference proceeding contribution › Research › peer-review

TY - GEN

T1 - Adaptive measurements and optimal states for quantum interferometry

AU - Berry, D. W.

AU - Wiseman, H. M.

PY - 2001/5

Y1 - 2001/5

N2 - Summary form only given. Interferometry is the basis of many high-precision measurements. The ultimate limit to the precision is due to quantum effects. This limit is most easily explored for a Mach-Zehnder interferometer The outputs of this device can be measured to yield an estimate φ of the phase difference φ between the two arms of the interferometer. It is well known that this can achieve the standard quantum limit for phase variance when an N-photon number state enters one input port. Several authors have proposed ways of reducing the phase variance to the Heisenberg limit. In this paper we show that there is a physical measurement scheme using photodetectors and feedback that is almost as good as the optimal measurement. The fundamental idea is that, in addition to the unknown phase we wish to measure, φ, in one arm of the interferometer, we introduce a known phase shift, Φ, into the other arm of the interferometer. After each photodetection we adjust this introduced phase shift in order to minimize the expected uncertainty of our best phase estimate φ after the next photodetection. This feedback process is uniquely defined using Bayesian statistics, and can be solved exactly for moderate photon numbers.

AB - Summary form only given. Interferometry is the basis of many high-precision measurements. The ultimate limit to the precision is due to quantum effects. This limit is most easily explored for a Mach-Zehnder interferometer The outputs of this device can be measured to yield an estimate φ of the phase difference φ between the two arms of the interferometer. It is well known that this can achieve the standard quantum limit for phase variance when an N-photon number state enters one input port. Several authors have proposed ways of reducing the phase variance to the Heisenberg limit. In this paper we show that there is a physical measurement scheme using photodetectors and feedback that is almost as good as the optimal measurement. The fundamental idea is that, in addition to the unknown phase we wish to measure, φ, in one arm of the interferometer, we introduce a known phase shift, Φ, into the other arm of the interferometer. After each photodetection we adjust this introduced phase shift in order to minimize the expected uncertainty of our best phase estimate φ after the next photodetection. This feedback process is uniquely defined using Bayesian statistics, and can be solved exactly for moderate photon numbers.

UR - http://www.scopus.com/inward/record.url?scp=84958254702&partnerID=8YFLogxK

U2 - 10.1109/QELS.2001.961853

DO - 10.1109/QELS.2001.961853

M3 - Conference proceeding contribution

SP - 60

EP - 61

BT - Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001

PB - Institute of Electrical and Electronics Engineers (IEEE)

CY - Piscataway, N.J.

ER -