Quantum reading for the practical man

Abstract

Quantum reading is the art of exploiting the quantum properties of light to retrieve classical information stored in an optical memory with low energy and high accuracy. It was shown that the optimal strategy for quantum reading of beamsplitters largely outperforms coherent strategies, further allowing for perfect quantum reading, but requires a source challenging from the experimental viewpoint. Focusing on probes — i.e. BAT states and entangled coherent states (ECS) — which are experimentally feasible with present quantum optical technology, but still allow for perfect quantum reading, we evaluate the tradeoffs between the energy and the probability of error (failure) in ambiguous (unambiguous) quantum reading. It turns out that BAT states outperform ECS in any regime except for the case of high-energy discrimination of two beamsplitters with similar reflectivities.