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Purity of Gaussian states: Measurement schemes and time evolution in noisy channels

SERAFINI, A; PARIS, M; ILLUMINATI, F; DE SIENA, S; (2003) Purity of Gaussian states: Measurement schemes and time evolution in noisy channels. PHYSICAL REVIEW A , 68 , Article 012314. 10.1103/PhysRevA.68.012314. Green open access

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Abstract

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme is tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and squeezed thermal baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state.

Type: Article
Title: Purity of Gaussian states: Measurement schemes and time evolution in noisy channels
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevA.68.012314
Publisher version: http://dx.doi.org/10.1103/PhysRevA.68.012314
Language: English
Additional information: © 2003 The American Physical Society
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/290476
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