Sensing with discrete time crystals

TL;DR

This paper demonstrates a highly frequency-selective quantum sensor using prethermal discrete time crystals in dipolar-coupled nuclear spins, achieving exponential lifetime enhancement and robust operation in a challenging frequency range.

Contribution

The authors introduce a novel PDTC-based quantum sensor that significantly improves lifetime and sensitivity for AC magnetic fields in the 0.5-50kHz range, with broad platform applicability.

Findings

Exponential increase in PDTC lifetime by up to three orders of magnitude.

Strong resonant response of the time crystalline order parameter to AC fields.

Sensor operates effectively in a challenging 0.5-50kHz frequency range.

Abstract

Prethermal discrete time crystals (PDTCs) are a nonequilibrium state of matter characterized by long-range spatiotemporal order, and exhibiting a subharmonic response stabilized by many-body interactions under periodic driving. The inherent robustness of time crystalline order to perturbations in the drive protocol makes DTCs promising for applications in quantum technologies. We exploit the susceptibility of PDTC order to deviations in its order parameter to devise highly frequency-selective quantum sensors for time-varying (AC) magnetic fields in a system of strongly-driven, dipolar-coupled 13C nuclear spins in diamond. Integrating a time-varying AC field into the PDTC allows us to exponentially increase its lifetime, with improvements of up to three orders of magnitude (44,204 cycles), and results in a strong resonant response in the time crystalline order parameter. The linewidth of our sensor is limited by the PDTC lifetime alone, as strong interspin interactions help stabilize DTC order. The sensor operates in the 0.5-50kHz range - a challenging frequency regime for sensors based on atomic vapor or electronic spins - and attains a competitive sensitivity. PDTC sensors are resilient to errors in the drive protocol and sample inhomogeneities, and are agnostic to the macroscopic details of the physical platform: the underlying physical principle applies equally to superconducting qubits, neutral atoms, and trapped ions.