IEEE - Aerospace and Electronic Systems - April 2020 - 20

The Quantum Illumination Story

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[46] Thus far in this article we have ignored-and, except here, we

ison with a classical (coherent-state source, coherent-

will continue to ignore-a target's effects on its return's
polarization and frequency. These effects, however, should be

detection receiver) system of the same transmitted
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included in a more complete QI analysis. For example, they

energy needed for entanglement distribution, their sys-

place additional burdens-polarization tracking and Doppler

tem does not represent a true benefit from using entan-

compensation-on Guha and Erkmen's OPA receiver.

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[52] Here, and in the next two sections, we forego consideration
of QI with SFG or FF-SFG reception owing to the dim pros-

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pects for implementing those receivers with current

1.3 gigabit-per-second secret-key rate over a 10 dB loss

technology.

channel,"

pﬃﬃﬃﬃﬃﬃﬃ
pﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ
GA a^Km þ GA À 1
[53] Preamplification yields a^amp
Km ¼
^amp
n^ampy
Km , is in a
Km for K ¼ R; I, where the noise mode, n

thermal state with average photon number Namp . Nonquantum-limited heterodyne detection of a^amp
Km results in a

Sci.

Technol.,

vol.

3,

2018,

[61] J. H. Shapiro, "Defeating passive eavesdropping with quantum illumination," Phys. Rev. A, 80, 2009, Art. no. 022320.
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classical complex-valued random variable, aKm , whose
statistics are equivalent to those of the operator

and S. A. Hamilton, "Quantum low probability
of intercept," J. Opt. Soc. Amer. B, vol. 36,

^dety
^det
a^amp
Km ,
Km for K ¼ R; I, where the noise mode, n
Km þ n

pp. B41-B50, 2019.

is in a thermal state with average photon number Ndet .

[63] J. H. Shapiro, "Quantum illumination: From enhanced tar-

The covariance matrices for the QCN and CCN radars

get detection to Gbps quantum key distribution," in Proc.

then follow directly from Tan et al.'s target-detection sce-

Conf. Lasers Electro-Opt., Technical Digest, Washington,

nario with GA NF  ðGA À 1ÞðNamp þ 1Þþ Ndet þ 1.
This measurement is quantum limited when both n^amp
Km

[64] J. H. Shapiro, "The quantum illumination story," in Proc.

and n^det
are in their vacuum
Km
Namp ¼ Ndet ¼ 0 lead to NF ¼ 1.

20

Quantum

Art. no. 25007.

states

so

DC, USA, 2017, Paper FTu3F.1.

that

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IEEE Conf. Microw., Antennas, Commun., Electron. Syst.,
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