Abstract
In most quantum sensing schemes, interactions between the constituent particles of the sensor are expected to lead to thermalisation and degraded sensitivity. However, recent theoretical and experimental work has shown that the phenomenon of quantum many-body scarring can slow down, or even prevent thermalisation. We show that scarring can be exploited for quantum sensing that is robust against certain strong interactions. In the ideal case of perfect scars with harmonic energy gaps, the optimal sensing time can diverge despite the strong interactions. We demonstrate the idea with two examples: a spin-1 model with Dzyaloshinskii-Moriya interaction, and a spin-1/2 mixed-field Ising model. We also briefly discuss some non-ideal perturbations, and the addition of periodic controls to suppress their effect on sensing.
Highlights
The estimation of physical quantities is an important task in many branches of science and technology
Strong Ising interactions between the spins are expected to lead to fast decoherence and thermalization. In this example the stronger couplings can extend the coherence time and enhance the quantum sensing. We show that this is due to the emergence of a set of quantum many-body scars in the “PXP” limit of the mixed-field Ising model
Quantum many-body scars are special eigenstates of a nonintegrable many-body system that, for certain initial states, can prevent or slow down thermalization. Since this is associated with long coherence times, scars can be exploited for quantum sensing. We demonstrate this for two example models: a spin-1 DzyaloshinskiiMoriya interaction (DMI) model and a spin-1/2 mixed-field Ising (MFI) model
Summary
The estimation of physical quantities is an important task in many branches of science and technology. Strong Ising interactions between the spins are expected to lead to fast decoherence and thermalization In this example the stronger couplings can extend the coherence time and enhance the quantum sensing. For a nonintegrable many-body system, the interactions Hint between particles can lead to decoherence and thermalization with respect to the expectation values O This is because the evolution generates entanglement in the system that makes information about the initial conditions inaccessible to the experimental observables O ∈ M. III and IV, we present two example models in which these criteria are satisfied, giving robust quantum sensing despite strong interactions in the many-body probe system Both examples suggest that in the ideal case (perfect scars with harmonic energy gaps and full overlap with the initial state), the optimal sensing time t∗ diverges
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