Continuous dynamical decoupling of a single diamond nitrogen-vacancy center spin with a mechanical resonator

TL;DR

This paper demonstrates that using a mechanical resonator to dress the spin states of a diamond NV center significantly extends its coherence time by reducing environmental magnetic noise effects.

Contribution

It introduces a novel method of continuous dynamical decoupling using mechanical stress to enhance NV center coherence, supported by a quantitative predictive model.

Findings

Prolonged dephasing time from 2.7 μs to 15 μs with mechanical driving.

Developed a model predicting the relationship between mechanical Rabi frequency and coherence time.

Identified magnetic field fluctuations and hyperfine interactions as limiting factors.

Abstract

Inhomogeneous dephasing from uncontrolled environmental noise can limit the coherence of a quantum sensor or qubit. For solid state spin qubits such as the nitrogen-vacancy (NV) center in diamond, a dominant source of environmental noise is magnetic field fluctuations due to nearby paramagnetic impurities and instabilities in a magnetic bias field. In this work, we use ac stress generated by a diamond mechanical resonator to engineer a dressed spin basis in which a single NV center qubit is less sensitive to its magnetic environment. For a qubit in the thermally isolated subspace of this protected basis, we prolong the dephasing time $T_2^*$ from $2.7\pm0.1$ $\mu$s to $15\pm1$ $\mu$s by dressing with a $\Omega=581\pm2$ kHz mechanical Rabi field. Furthermore, we develop a model that quantitatively predicts the relationship between $\Omega$ and $T_2^*$ in the dressed basis. Our model suggests that a combination of magnetic field fluctuations and hyperfine coupling to nearby nuclear spins limits the protected coherence time over the range of $\Omega$ accessed here. We show that amplitude noise in $\Omega$ will dominate the dephasing for larger driving fields.