Quantum-Dense Metrology

TL;DR

This paper demonstrates quantum dense metrology using a laser interferometer to measure two non-commuting observables simultaneously with uncertainties below the quantum ground state, enhancing detection capabilities.

Contribution

It introduces a novel quantum dense metrology technique that measures two non-commuting observables simultaneously, surpassing previous single-observable measurement limits.

Findings

Measured two non-commuting observables with uncertainties below the quantum ground state.

Successfully distinguished between phase signals and parasitic signals.

Potential application to improve gravitational-wave detectors.

Abstract

Quantum metrology utilizes entanglement for improving the sensitivity of measurements. Up to now the focus has been on the measurement of just one out of two non-commuting observables. Here we demonstrate a laser interferometer that provides information about two non-commuting observables, with uncertainties below that of the meter's quantum ground state. Our experiment is a proof-of-principle of quantum dense metrology, and uses the additional information to distinguish between the actual phase signal and a parasitic signal due to scattered and frequency shifted photons. Our approach can be readily applied to improve squeezed-light enhanced gravitational-wave detectors at non-quantum noise limited detection frequencies in terms of a sub shot-noise veto-channel.