Optimal environment localization

Jason L. Pereira, Quntao Zhuang, Stefano Pirandola

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Quantum channels model many physical processes. For this reason, hypothesis testing between quantum channels is a fundamental task in quantum information theory. Here we consider the paradigmatic case of channel position finding, where the aim is to determine the position of a target quantum channel within a sequence of background channels. We explore this model in the setting of bosonic systems, considering Gaussian channels with the same transmissivity (or gain) but different levels of environmental noise. Thus, the goal of the problem becomes detecting the position of a target environment among a number of identical background environments, all acting on an input multimode system. We derive bounds for the ultimate error probability affecting this multiary discrimination problem and find an analytic condition for quantum advantage over protocols involving classical input states. We also design an explicit protocol that gives numerical bounds on the ultimate error probability and often achieves quantum advantage. Finally, we consider direct applications of the model for tasks of thermal imaging (finding a warmer pixel in a colder background) and quantum communication (for localizing a different level of noise in a sequence of lines or a frequency spectrum).

Original languageEnglish (US)
Article number043189
JournalPhysical Review Research
Issue number4
StatePublished - Nov 5 2020

ASJC Scopus subject areas

  • General Physics and Astronomy


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