Quantum Illumination with Gaussian States

Abstract

An optical transmitter irradiates a target region containing a bright thermal-noise bath in which a low-reflectivity object might be embedded. The light received from this region is used to decide whether the object is present or absent. The performance achieved using a coherent-state transmitter is compared with that of a quantum-illumination transmitter, i.e., one that employs the signal beam obtained from spontaneous parametric down-conversion. By making the optimum joint measurement on the light received from the target region together with the retained spontaneous parametric down-conversion idler beam, the quantum-illumination system realizes a 6 dB advantage in the error-probability exponent over the optimum reception coherent-state system. This advantage accrues despite there being no entanglement between the light collected from the target region and the retained idler beam.

Upper and lower bounds on optimal success probability of quantum state discrimination with and without inconclusive results

“…Assume that {Ê k } M−1 k=1 exists such that Eqs. (25) and (26) hold. Also, let Π = {Π m } be the POVM defined by Eq.…”

“…Instead of computing an exact optimal success probabilities, several previous studies have given its upper and/or lower bounds [20][21][22][23][24][25][26][27][28]. These methods are especially useful for large scale problems of which it is hard to compute an exact value within feasible time; for example, in Ref.…”

“…These methods are especially useful for large scale problems of which it is hard to compute an exact value within feasible time; for example, in Ref. [25], bounds are effectively used for comparing optimal success probabilities with different optical states. In the case of minimum-error measurements, Qiu et al compared some of these upper bounds with each other, and derived another upper bound [27], which improves some upper bounds in some cases.…”

Realizable receivers for discriminating coherent and multicopy quantum states near the quantum limit

“…(13) of the main text. A lower bound on the EPE ξ SWN [{α m }] of the SWN receiver can be obtained by inserting the right-hand side of (A.26) into (5). Only the term that decays the slowest with ∆ (or equivalently, with N ) survives in the limit of N → ∞, so that 27) which is eq.…”

“…The task of optimally discriminating between unknown nonorthogonal quantum states by making appropriate quantum measurements [1][2][3][4] is a fundamental primitive underlying many quantum information processing tasks, including communication [1], sensing and metrology [4,5], and various cryptographic protocols [6]. The paradigmatic problem of the so-called quantum detection theory [1] is to determine the quantum measurement, specified by a mathematical object known as a positive operator-valued measure (POVM) [4,7], that minimizes the average error probability in discriminating a given ensemble of states.…”