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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Continuous measurement of photon number with double registration of counts

A. Lukš, Vlasta Peřinová

Published Jul 19, 1999• 0 citations
Publisher

Abstract

We investigate the role of stable atomic states in the microscopic theory of continuous quantum-nondemolition measurement of photon number. Conventionally, their energies are equal. When the stable states correspond to different energy levels, the measured mode is effectively incoherently coupled to another mode.
DOI
10.1117/12.354819

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This paper proposes a microscopic model for the continuous measurement of photon numbers where the continuous measurement is simulated by a sequence of infinitesimal processes. Each process is composed of a unitary evolution for the coupled system, which consists of the field and the measuring apparatus, followed by a projection according to the readout of the measuring apparatus. The proposed model consists of two-level atoms that are coupled one by one with an optical cavity field via the electric-dipole interaction. Each atomic level is then read out after the interaction, causing a nonunitary state reduction of the field. In particular, it is shown that this microscopic model leads to the Srinivas-Davies model that has been postulated for the photodetection process.
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We propose a quantum nondemolition measurement of the photon-number distribution for a two-mode cavity field. In the scheme two sequences of two-level atoms interact dispersively with the respective cavity modes and resonantly with two classical fields, and then are detected continually. The field finally reduces to a two-mode Fock state. The probability of collapsing to a given Fock state is determined by the initial photon-number distribution. The scheme can be easily generalized to a field with N modes.