Creating and Verifying a Quantum Superposition in a Micro-optomechanical System

TL;DR

This paper analyzes the creation and verification of quantum superpositions in micro-optomechanical systems, emphasizing the effects of temperature, decoherence, and cooling techniques to demonstrate non-classical states.

Contribution

It provides a detailed analysis of temperature effects, decoherence, and cooling methods for realizing and verifying quantum superpositions in micro-optomechanical systems.

Findings

Finite temperature impacts interpretation of experiments.

Ground state cooling is necessary for unambiguous superposition demonstration.

Decoherence timescales are estimated considering environmental and gravitational effects.

Abstract

Micro-optomechanical systems are central to a number of recent proposals for realizing quantum mechanical effects in relatively massive systems. Here we focus on a particular class of experiments which aim to demonstrate massive quantum superpositions, although the obtained results should be generalizable to similar experiments. We analyze in detail the effects of finite temperature on the interpretation of the experiment, and obtain a lower bound on the degree of non-classicality of the cantilever. Although it is possible to measure the quantum decoherence time when starting from finite temperature, an unambiguous demonstration of a quantum superposition requires the mechanical resonator to be in or near the ground state. This can be achieved by optical cooling of the fundamental mode, which also provides a method to measure the mean phonon number in that mode. We also calculate the rate of environmentally induced decoherence and estimate the timescale for gravitational collapse mechanisms as proposed by Penrose and Diosi. In view of recent experimental advances, practical considerations for the realization of the described experiment are discussed.