1,347 research outputs found
Entanglement as a resource for discrimination of classical environments
We address extended systems interacting with classical fluctuating
environments and analyze the use of quantum probes to discriminate local noise,
described by independent fluctuating fields, from common noise, corresponding
to the interaction with a common one. In particular, we consider a bipartite
system made of two non interacting harmonic oscillators and assess
discrimination strategies based on homodyne detection, comparing their
performances with the ultimate bounds on the error probabilities of
quantum-limited measurements. We analyze in details the use of Gaussian probes,
with emphasis on experimentally friendly signals. Our results show that a joint
measurement of the position-quadrature on the two oscillators outperforms any
other homodyne-based scheme for any input Gaussian state
Large Deviations Performance of Consensus+Innovations Distributed Detection with Non-Gaussian Observations
We establish the large deviations asymptotic performance (error exponent) of
consensus+innovations distributed detection over random networks with generic
(non-Gaussian) sensor observations. At each time instant, sensors 1) combine
theirs with the decision variables of their neighbors (consensus) and 2)
assimilate their new observations (innovations). This paper shows for general
non-Gaussian distributions that consensus+innovations distributed detection
exhibits a phase transition behavior with respect to the network degree of
connectivity. Above a threshold, distributed is as good as centralized, with
the same optimal asymptotic detection performance, but, below the threshold,
distributed detection is suboptimal with respect to centralized detection. We
determine this threshold and quantify the performance loss below threshold.
Finally, we show the dependence of the threshold and performance on the
distribution of the observations: distributed detectors over the same random
network, but with different observations' distributions, for example, Gaussian,
Laplace, or quantized, may have different asymptotic performance, even when the
corresponding centralized detectors have the same asymptotic performance.Comment: 30 pages, journal, submitted Nov 17, 2011; revised Apr 3, 201
Quantum reading of digital memory with non-Gaussian entangled light
It has been shown recently (Phys. Rev. Lett. 106, 090504 (2011)) that
entangled light with Einstein-Podolsky-Rosen (EPR) correlations retrieves
information from digital memory better than any classical light. In identifying
this, a model of digital memory with each cell consisting of reflecting medium
with two reflectivities (each memory cell encoding the binary numbers 0 or 1)
is employed. The readout of binary memory essentially corresponds to
discrimination of two Bosonic attenuator channels characterized by different
reflectivities. The model requires an entire mathematical paraphernalia of
continuous variable Gaussian setting for its analysis, when arbitrary values of
reflectivities are considered. Here we restrict to a basic quantum read-out
mechanism with non-Gaussian entangled states of light, with the binary channels
to be discriminated being ideal memory characterized by reflectivity one i.e.,
an identity channel and thermal noise channel, where the signal light
illuminating the memory location gets completely lost (zero reflectivity) and
only a white thermal noise hitting the upper side of the memory reaches the
decoder. We compare the quantum reading efficiency of entangled light with any
classical source of light in this model. We show that entangled transmitters
offer better reading performance than any classical transmitters of light in
the regime of low signal intensity.Comment: 7 pages, 6 figures, To appear in Phys. Rev.
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