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

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* sub(2) from 2.7 + or - 0.1 to 15 + or - 1 mu s by dressing with a [Omega]/2[pi] = 581 + or - 2 kHz mechanical Rabi field. Furthermore, we develop a model that quantitatively predicts the relationship between [Omega] and T* sub(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.