Properties of a monolithic sapphire parametric transducer: prospects of measuring the standard quantum limit

TL;DR

This paper investigates the properties of a monolithic sapphire transducer with high quality factors, demonstrating its potential to measure quantum noise limits and proposing a method to verify quantum-limited back action.

Contribution

It introduces the monolithic sapphire transducer's high-Q characteristics and a novel approach to determine if its back action is quantum limited.

Findings

Mechanical quality factor of 6.10^8 at 4 K

Potential to measure noise at the standard quantum limit

Proposes a new method to verify quantum-limited back action

Abstract

To measure the standard quantum limit (SQL) a high quality transducer must be coupled to a high quality mechanical system. Due to its monolithic nature, the monolithic sapphire transducer (MST) has high quality factors for both types of resonances. Single loop suspension is shown to yield a mechanical quality factor of 6.10^8 at 4 K. From standard analysis we show the MST has the potential to measure noise fluctuations of the mechanical oscillator at the SQL. also, we point out a new way to determine if the transducer back action is quantum limited. We show that if the fluctuations are at the quantum limit, then the amplitude of the oscillation will be amplified by the ratio of the ringdown time to the measurement time, which is an inherently easier measurement.