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IEEE Transactions on Information Theory

Information in quantum optical binary communications

Apostol Vourdas

Published Jan 1, 1990• 6 citations
Publisher

Abstract

A quantum mechanical formalism for the calculation of the transmitted information per symbol in optical binary communications is presented. The concavity property is used to calculate the maximum entropy, from which the average entropy is subtracted to calculate the information per symbol. The proposed formalism is applied to the number of eigenstate signals in thermal noise and squeezed signals in thermal noise. The error probability for these cases is calculated. It is found that squeezing can improve the performance of optical communications.>

DOI
10.1109/18.50394

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A quantum mechanical formalism for the calculation of the transmitted information per symbol in optical binary communications is presented. The concavity property is used to calculate the maximum entropy, from which the average entropy is subtracted to calculate the information per symbol. The proposed formalism is applied to the number of eigenstate signals in thermal noise and squeezed signals in thermal noise. The error probability for these cases is calculated. It is found that squeezing can improve the performance of optical communications.>
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The description of Gaussian noise for single-mode quantum fields is briefly reviewed and applied to calculate the maximal information properties of three quantum communication channels degraded by Gaussian noise. These channels are based on (i) heterodyne detection of coherent states, (ii) homodyne detection of squeezed states, and (iii) photodetection of number states. It is found that each channel can outperform the others for a given noise level, where the optimum channel is essentially determined by the product of the average noise and signal energies.
The performance of two-photon coherent-state (TCS) signals and integral-quantum signals in unimodal and bimodal free-space optical communications is compared with that of ordinary ,coherent signals under the constraint of fixed average error probability. For the unimodal channel of known phase the minimum attainable error probability for both on-off and antipodal TCS signals received in thermal noise is calculated by applying perturbation theory to the detection operator equation. For unimodal antipodal TCS signaling the threshold receiver is also considered. For channels of random phase the optimum photon-counting receiver is analyzed. In all cases the advantage of the nonclassical signal over an ordinary coherent signal vanishes as the transmittance of the channel goes to zero.
A squeezed-displaced state can be used as an optical signal for efficient binary quantum optical communication. Here, we consider quantum optical communication where an atomic indirect measurement is used to decide the message encoded in a binary phase-shift-keying signal composed of squeezed-displaced states, and show that the incorrect decision probability of an atomic indirect measurement can be less than that of a homodyne measurement. We further show that an atomic indirect measurement can lower the incorrect decision probability even when the quantum channel is exposed to weak phase-diffusion noise.