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IEEE/LEOS Summer Topical Meetings

Entanglement and decoherence in optical amplifiers

J. D. Franson

Published Jul 1, 2017• 0 citations
Publisher

Abstract

An ideal optical amplifier is generally considered to be a linear device. We show that entanglement between the signal and idler modes can produce nonlinear behavior and decoherence even for small gains where the added noise is negligible.
DOI
10.1109/phosst.2017.8012666

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In an ideal linear amplifier, the output signal is linearly related to the input signal with an additive noise that is independent of the input. The decoherence of a quantum-mechanical state as a result of optical amplification is usually assumed to be due to the addition of quantum noise. Here we show that entanglement between the input signal and the amplifying medium can produce an exponentially-large amount of decoherence in an ideal optical amplifier even when the gain is arbitrarily close to unity and the added noise is negligible. These effects occur for macroscopic superposition states, where even a small amount of gain can leave a significant amount of which-path information in the environment. Our results show that the usual input/output relation of a linear amplifier does not provide a complete description of the output state when post-selection is used.
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