# Measurement of motion beyond the quantum limit by transient amplification

## TL;DR

This paper introduces transient electromechanical amplification (TEA), a nearly noiseless pulsed measurement technique that surpasses the quantum limit, enabling detailed phase-space analysis and direct observation of mechanical squeezing.

## Contribution

The authors develop and demonstrate TEA, a novel method for quantum-limited, nearly noiseless measurement of mechanical motion that surpasses previous measurement limits.

## Key findings

- TEA achieves a total added noise of -8.5 dB relative to zero-point motion.
- TEA allows tomographic reconstruction of a squeezed state's density matrix.
- Direct observation of a 2.8 dB squeezed variance below zero-point motion.

## Abstract

Through simultaneous but unequal electromechanical amplification and cooling processes, we create a method for nearly noiseless pulsed measurement of mechanical motion. We use transient electromechanical amplification (TEA) to monitor a single motional quadrature with a total added noise $-8.5\pm2.0$ dB relative to the zero-point motion of the oscillator, or equivalently the quantum limit for simultaneous measurement of both mechanical quadratures. We demonstrate that TEA can be used to resolve fine structure in the phase-space of a mechanical oscillator by tomographically reconstructing the density matrix of a squeezed state of motion. Without any inference or subtraction of noise, we directly observe a squeezed variance $2.8\pm 0.3$ dB below the oscillator's zero-point motion.