On the limitations of a measurement-assisted optomechanical route to quantum macroscopicity of superposition states

TL;DR

This paper critically examines the feasibility of achieving genuine macroscopic quantum superpositions in optomechanical systems, highlighting the stringent experimental conditions required and analyzing the limitations of measurement-assisted approaches.

Contribution

It introduces a phase space-based figure of merit to evaluate macroscopic quantum states and assesses the conditions under which optomechanical systems can produce genuine macroscopic superpositions.

Findings

Strong single-photon coupling can produce macroscopically quantum states.

Genuine macroscopic superpositions require demanding experimental conditions.

Measurement-assisted methods have limitations in achieving true macroscopic quantum states.

Abstract

Optomechanics is currently believed to provide a promising route towards the achievement of genuine quantum effects at the large, massive-system scale. By using a recently proposed figure of merit that is well suited to address continuous-variable systems, in this paper we analyze the requirements needed for the state of a mechanical mode (embodied by an end-cavity cantilever or a membrane placed within an optical cavity) to be qualified as macroscopic. We show that, according to the phase space-based criterion that we have chosen for our quantitative analysis, the state achieved through strong single-photon radiation-pressure coupling to a quantized field of light and conditioned by measurements operated on the latter might be interpreted as macroscopically quantum. In general, though, genuine macroscopic quantum superpositions appear to be possible only under quite demanding experimental conditions.