Defeating passive eavesdropping with quantum illumination

Physical Review A - Atomic, Molecular, and Optical Physics

Volumn 80, Issue 2, 2009, Pages

  Shapiro, Jeffrey H ^a  

^a MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMPLIFIER NOISE; BINARY PHASE-SHIFT KEYING; DOWN CONVERTERS; EN-ROUTE; ERROR PROBABILITIES; IDLER BEAMS; INFORMATION BIT; LOW LOSS; ORDERS OF MAGNITUDE;

HELIUM; LIGHT; LIGHT TRANSMISSION; SECURITY SYSTEMS;

PROBABILITY;

EID: 68949098553     PISSN: 10502947     EISSN: 10941622     Source Type: Journal    
DOI: 10.1103/PhysRevA.80.022320     Document Type: Article

References (19)

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8. This state has maximum quadrature entanglement for its average photon number. Its closest classical-state counterpart is the zero-mean, jointly Gaussian state whose Wigner-distribution covariance is given by Eq. 1 with Cq replaced by Cc 2 NS. For low-brightness operation, wherein NS 1 prevails, we have Cq Cc.
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10. At near infrared through ultraviolet wavelengths, background light will be sufficiently weak that it can be ignored. For example, a typical daytime spectral radiance value of 10 W/ m2 srμm at 1.55 μm wavelength [N. S. Kopeika and J. Bordogna, Proc. IEEE 58, 1571 (1970)] leads to e Bm † e Bm ∼ 10-6 for a line-of-sight terrestrial link; nighttime values are orders of magnitude lower. Room-temperature thermal noise is even weaker, viz., e Bm † e Bm 4× 10-14 at 1.55 μm wavelength for a 300 K noise temperature. Thus, our pure-loss (noiseless) channel model will suffice so long as NS 10-6.
11. For NB κG, this state is classical, i.e., it has a proper P representation, hence it is not entangled.
12. This assumption maximizes the information gained by a passive eavesdropper. The error probability disparity-between Alice and Eve's receivers-will only increase if Eve's coupling to either Alice or Bob's transmission is reduced from its theoretical maximum.
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17. Our use of modal representations to describe OPA operation and the subsequent photon-counting measurement does not imply that separate amplifiers are required for each mode pair nor that a separate photon-counting measurement must be made for each output mode. A cw-pumped OPA can be used to perform the desired operation on the return and idler beams, and one photodetector can be used to obtain the total photon count. These results follow immediately from modal expansions for the relevant positive-frequency field operators. For example, with E (t) m a m′ e-j ωm t /T representing the positive-frequency field operator for a single T -sec-long bit interval at the OPA's output, our OPA receiver only needs to measure the total photon-count operator dt E † (t) E t).
18. The Bhattacharyya bound is the Chernoff bound with s=1/2 used even when it is not the optimum choice.
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