Quantum illumination for enhanced detection of Rayleighfading targets
Abstract
Quantum illumination (QI) is an entanglementenhanced sensing system whose performance advantage over a comparable classical system survives its usage in an entanglementbreaking scenario plagued by loss and noise. In particular, QI's errorprobability exponent for discriminating between equally likely hypotheses of target absence or presence is 6 dB higher than that of the optimum classical system using the same transmitted power. This performance advantage, however, presumes that the target return, when present, has known amplitude and phase, a situation that seldom occurs in light detection and ranging (lidar) applications. At lidar wavelengths, most target surfaces are sufficiently rough that their returns are speckled, i.e., they have Rayleighdistributed amplitudes and uniformly distributed phases. QI's optical parametric amplifier receiver—which affords a 3 dB betterthanclassical errorprobability exponent for a return with known amplitude and phase—fails to offer any performance gain for Rayleighfading targets. We show that the sumfrequency generation receiver [Zhuang et al., Phys. Rev. Lett. 118, 040801 (2017), 10.1103/PhysRevLett.118.040801]—whose errorprobability exponent for a nonfading target achieves QI's full 6 dB advantage over optimum classical operation—outperforms the classical system for Rayleighfading targets. In this case, QI's advantage is subexponential: its error probability is lower than the classical system's by a factor of 1 /ln(M κ ̄N_{S}/N_{B}) , when M κ ̄N_{S}/N_{B}≫1 , with M ≫1 being the QI transmitter's timebandwidth product, N_{S}≪1 its brightness, κ ̄ the target return's average intensity, and N_{B} the background light's brightness.
 Publication:

Physical Review A
 Pub Date:
 August 2017
 DOI:
 10.1103/PhysRevA.96.020302
 arXiv:
 arXiv:1706.05561
 Bibcode:
 2017PhRvA..96b0302Z
 Keywords:

 Quantum Physics
 EPrint:
 7 pages, 3 figures