Revealing interference by continuous variable discordant states

TL;DR

This paper demonstrates that interference effects in Gaussian states can be revealed using discordant states, even when traditional indicators show no correlations, through theoretical proof and experimental validation involving thermal states.

Contribution

It introduces a method to reveal interference using Gaussian discordant states with a third beam, expanding understanding of quantum correlations in continuous variables.

Findings

Interference can be detected with discordant states even when no correlations are visible.

Experimental results confirm the theoretical prediction using thermal states.

Gaussian discordant states can be useful for specific quantum tasks despite positive P-function.

Abstract

In general, a pair of uncorrelated Gaussian states mixed in a beam splitter produces a correlated state at the output. However, when the inputs are identical Gaussian states the output state is equal to the input, and no correlations appear, as the interference had not taken place. On the other hand, since physical phenomena do have observable effects, and the beam splitter is there, a question arises on how to reveal the interference between the two beams. We prove theoretically and demonstrate experimentally that this is possible if at least one of the two beams is prepared in a discordant, i.e. Gaussian correlated, state with a third beam. We also apply the same technique to reveal the erasure of polarization information. Our experiments involves thermal states and the results show that Gaussian discordant states, even when they show a positive Glauber P-function, may be useful to achieve specific tasks.