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arXiv:1609.00913

Quantum coherence of Gaussian states

Daniela Buono, Gaetano Nocerino, Giuseppe Petrillo, Gianpaolo Torre, Giuseppe Zonzo, Fabrizio Illuminati

Published Sep 4, 2016• 10 citations
arXivHTMLPDF

Abstract

We introduce a geometric quantification of quantum coherence in single-mode Gaussian states and we investigate the behavior of distance measures as functions of different physical parameters. In the case of squeezed thermal states, we observe that re-quantization yields an effect of noise-enhanced quantum coherence for increasing thermal photon number.

DOI
10.48550/arxiv.1609.00913

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We calculate the quantum mechanical, temporal second-order coherence function for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz. a displaced–squeezed thermal state. The calculation involves first dynamical generation at time t of the Gaussian state from an initial thermal state and subsequent measurements of two photons a time τ≥0 apart. The generation of the Gaussian state by the parametric amplifier insures that the temporal second-order coherence function depends only on τ, via τ/t, for the given Gaussian state parameters, Gaussian state preparation time t, and average number n¯ of thermal photons. It is interesting that the time evolution for displaced thermal states shows a power decay in τ/t rather than an exponential one as is the case for general, displaced–squeezed thermal states.
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