Data di Pubblicazione:
2011
Citazione:
Optimal detection of losses by thermal probes / C. Invernizzi, M. G. A. Paris, S. Pirandola. - In: PHYSICAL REVIEW A. - ISSN 1050-2947. - 84:2(2011), pp. 022334.022334.1-022334.022334.12. [10.1103/PhysRevA.84.022334]
Abstract:
We consider the discrimination of lossy bosonic channels and focus on the case when one of the values for
the loss parameter is zero, i.e., we address the detection of a possible loss against the alternative hypothesis of
an ideal lossless channel. This discrimination is performed by inputting one- or two-mode squeezed thermal
states with fixed total energy. By optimizing over this class of states, we find that the optimal inputs are pure,
thus corresponding to single- and two-mode squeezed vacuum states. In particular, we show that, for any value
of the damping rate smaller than a critical value, there is a threshold on the energy that makes the two-mode
squeezed vacuum state more convenient than the corresponding single-mode state, whereas for damping larger
than this critical value, two-mode squeezed vacua are always better. We then consider the discrimination in
realistic conditions, where it is unlikely to have pure squeezing. Thus, by fixing both input energy and squeezing,
we show that two-mode squeezed thermal states are always better than their single-mode counterpart when all the
thermal photons are directed into the dissipative channel. Aside from that, this result also holds approximately
for unbalanced distribution of the thermal photons. Finally, we also investigate the role of correlations in the
improvement of detection. For fixed input squeezing (single mode or two mode), we find that the reduction
of the quantum Chernoff bound is a monotone function of the two-mode entanglement as well as the quantum
mutual information and the quantum discord. We thus verify that employing squeezing in the form of correlations
(quantum or classical) is always a resource for loss detection whenever squeezed thermal states are taken as input.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
C. Invernizzi, M.G.A. Paris, S. Pirandola
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