Purity of Gaussian states: Measurement schemes and time evolution in noisy channels
- Quantum Optics and Information Group, INFM UdR di Pavia, I-27100 Pavia (Italy)
- Dipartimento di Fisica 'E. R. Caianiello', Universita di Salerno, INFM UdR Salerno, INFN Sez. Napoli, Grupo Collegato Salerno, Via S. Allende, 84081 Baronissi, SA (Italy)
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 are 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 in 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.
- OSTI ID:
- 20639880
- Journal Information:
- Physical Review. A, Vol. 68, Issue 1; Other Information: DOI: 10.1103/PhysRevA.68.012314; (c) 2003 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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