653 research outputs found
Quantum Binary Decision for Driven Harmonic Oscillator
We address the problem of determining whether or not a harmonic oscillator
has been perturbed by an external force. Quantum detection and estimation
theory has been used in devising optimum measurement schemes. Detection
probability has been evaluated for different initial state preparations of
oscillator. The corresponding lower bounds on minimum detectable perturbation
intensity has been evaluated and a general bound for random phase perturbation
has been also induced.Comment: Latex 5 figs -- More info at http://enterprise.pv.infn.it/~pari
Unitary local invariance
We address unitary local (UL) invariance of bipartite pure states. Given a
bipartite state the complete
characterization of the class of local unitaries for which
is obtained.The two relevant parameters are
the rank of the matrix , , and the number of its
equal singular values, {\em i.e.} the degeneracy of the eigenvalues of the
partial traces of .Comment: Revised version. Accepted for publication Int. J. Quant. In
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