Full monitoring of phase-space trajectories with 10dB-sub-Heisenberg imprecision

TL;DR

This paper demonstrates an optical measurement system capable of monitoring quantum state displacements in phase space with 10dB below the Heisenberg limit, utilizing entanglement to surpass traditional measurement precision bounds.

Contribution

It introduces a novel measurement setup that achieves 10dB sub-Heisenberg imprecision using entanglement, enabling more precise quantum state monitoring.

Findings

Achieved 10dB reduction in measurement imprecision below the Heisenberg limit.

Enabled simultaneous monitoring of quantum displacements over time.

Supports advancements in quantum metrology and measurement-based quantum computing.

Abstract

The change of a quantum state can generally only be fully monitored through simultaneous measurements of two non-commuting observables X and Y spanning a phase space. A measurement device that is coupled to the thermal environment provides at a time a pair of values that have a minimal uncertainty product set by the Heisenberg uncertainty relation, which limits the precision of the monitoring. Here we report on an optical measurement setup that is able to monitor the time dependent change of the quantum state's displacement in phase space (< X (t)>; < Y (t)>) with an imprecision 10\,dB below the Heisenberg uncertainty limit. Our setup provides pairs of values (X(t_i); Y(t_i)) from simultaneous measurements at subsequent times t_i. The measurement references are not coupled to the thermal environment but are established by an entangled quantum state. Our achievement of a tenfold reduced quantum imprecision in monitoring arbitrary time-dependent displacements supports the potential of the quantum technology required for entanglement-enhanced metrology and sensing as well as measurement-based quantum computing.