November 2022
Spotlight Summary by Cosmo Lupo
Stealth in quantum illumination with a probabilistic mixed strategy
Quantum illumination allows us to detect a faint target in the presence of substantial background noise. It exploits a pair of entangled photons, one of which is sent towards the target, and the other retained as a reference. If the target is there, with non-zero probability the probe photon will be reflected back. The returning photon is fundamentally different from those coming from the background noise, as it is the only one that is quantum-correlated with the reference. These quantum correlations can be detected in principle and exploited to improve the signal-to-noise ratio and reduce the probability of missing the target.
This paper formulates the following fundamental question: is it possible for the target to use some sort of camouflage to effectively hide its presence? To address this question, the author presents a probabilistic mixed strategy where the target intentionally modulates its reflectivity, yet in a random way. In particular, with probability 1-q the target nullifies its reflectivity, as if nothing were there. By employing this strategy, the author shows that the probability of detecting the target by illuminating it with M entangled photons is as low as random guessing. However, this camouflage strategy works only if q is chosen smaller than 1/M, which implicitly implies that the target needs to know in advance the value of M. This latter assumption may be justified in some scenario and less justified in others. Nevertheless, the paper invites us to think outside the box and to search for subtle strategies to hide from an all-powerful quantum adversary.
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This paper formulates the following fundamental question: is it possible for the target to use some sort of camouflage to effectively hide its presence? To address this question, the author presents a probabilistic mixed strategy where the target intentionally modulates its reflectivity, yet in a random way. In particular, with probability 1-q the target nullifies its reflectivity, as if nothing were there. By employing this strategy, the author shows that the probability of detecting the target by illuminating it with M entangled photons is as low as random guessing. However, this camouflage strategy works only if q is chosen smaller than 1/M, which implicitly implies that the target needs to know in advance the value of M. This latter assumption may be justified in some scenario and less justified in others. Nevertheless, the paper invites us to think outside the box and to search for subtle strategies to hide from an all-powerful quantum adversary.
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Article Information
Stealth in quantum illumination with a probabilistic mixed strategy
ShengLi Zhang
J. Opt. Soc. Am. B 39(7) 1799-1806 (2022) View: Abstract | HTML | PDF