Quantum Asymmetry and Noisy Multimode Interferometry

Quantum asymmetry is a physical resource that coincides with the amount of coherence between the eigenspaces of a generator responsible for phase encoding in interferometric experiments. We highlight an apparently counterintuitive behavior that the asymmetry may increase as a result of a decrease of coherence inside a degenerate subspace. We intuitively explain and illustrate the phenomena by performing a three-mode single-photon interferometric experiment, where one arm carries the signal and two noisy reference arms have fluctuating phases. We show that the source of the observed sensitivity improvement is the reduction of correlations between these fluctuations and comment on the impact of the effect when moving from the single-photon quantum level to the classical regime. Finally, we also establish the analogy of the effect in the case of entanglement resource theory.

Automated summary

This article introduces quantum asymmetry and its relationship with coherence, emphasizing the counterintuitive phenomenon where asymmetry may increase with a decrease in coherence. Through a photon interferometric experiment, the authors intuitively explain and demonstrate this phenomenon. They also discuss the impact of this effect in transitioning from the quantum level to the classical regime and establish an analogy in the case of entanglement resource theory.