Quantum metrology with boundary time crystals

TL;DR

This paper demonstrates how boundary time crystals, a type of dissipative quantum phase, can be used to achieve quantum-enhanced sensing by exploiting decoherence, with practical advantages like independence from initial states.

Contribution

It introduces a novel sensing scheme utilizing boundary time crystals and characterizes its quantum-enhanced sensitivity through quantum Fisher information and critical exponents.

Findings

Quantum Fisher information indicates enhanced sensitivity at the phase transition.

The transition exhibits second-order critical behavior with identifiable exponents.

The scheme is robust, initialization-independent, and practically measurable.

Abstract

Quantum sensing is one of the arenas that exemplifies the superiority of quantum technologies over their classical counterparts. Such superiority, however, can be diminished due to unavoidable noise and decoherence of the probe. Thus, metrological strategies to fight against or profit from decoherence are highly desirable. This is the case of certain types of decoherence-driven many-body systems supporting dissipative phase transitions, which might be helpful for sensing. Boundary time crystals are exotic dissipative phases of matter in which the time-translational symmetry is broken, and long-lasting oscillations emerge in open quantum systems at the thermodynamic limit. We show that the transition from a symmetry unbroken into a boundary time crystal phase, described by a second-order transition, reveals quantum-enhanced sensitivity quantified through quantum Fisher information. We also determine the critical exponents of the system and establish their relationship. Our scheme is indeed a demonstration of harnessing decoherence for achieving quantum-enhanced sensitivity. From a practical perspective, it has the advantage of being independent of initialization and can be captured by a simple measurement.