## Abstract

The usual open-loop quantum and semiclassical theories of light detection are extended to include closed-loop operation in which there is feedback from the detector to the source. It is shown that the unmistakable signatures of nonclassical light associated with open-loop detection, such as sub-shot-noise spectra and sub-Poisson photocounts, do not carry over to closed-loop systems. This behavior is illustrated through quantitatively indistinguishable quantum and semiclassical analyses of two recent closed-loop experiments in which sub-Poisson photocount statistics were produced. It turns out that if the open-loop illumination does not require the use of quantum photodetection theory, then neither does the closed-loop illumination. Conversely, if the open-loop illumination is nonclassical, then the closed-loop behavior must be analyzed quantum mechanically. The use of nonclassical field correlations to obtain light beams that give sub-Poisson open-loop photocounts from these closed-loop arrangements is discussed and generalized into a synthesis procedure for producing light beams with arbitrary open-loop photocount statistics.

Original language | English (US) |
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Pages (from-to) | 1604-1620 |

Number of pages | 17 |

Journal | Journal of the Optical Society of America B: Optical Physics |

Volume | 4 |

Issue number | 10 |

DOIs | |

State | Published - Jan 1 1987 |

## ASJC Scopus subject areas

- Statistical and Nonlinear Physics
- Atomic and Molecular Physics, and Optics