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

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 ± 0.1 µs to 15 ± 1 µs by dressing with a Ω = 581 ± 2 kHz mechanical Rabi field. Furthermore, we develop a model that quantitatively predicts the relationship between Ω 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 Ω accessed here. We show that amplitude noise in Ω will dominate the dephasing for larger driving fields.PACS numbers: 76.30. Mi, 63.20.kp, 76.60.Jx The triplet spin of the nitrogen-vacancy (NV) center in diamond has become a foundational component in both quantum metrology and future quantum information technologies. For sensing, the inhomogeneous dephasing time T * 2 of an NV center spin qubit can limit sensitivity to quasi-static fields. For quantum information applications, T * 2 can limit the number and the duration of gate operations that a qubit can undergo. Pulsed dynamical decoupling (PDD) techniques based on the principle of spin echoes refocus inhomogeneous dephasing and can extend T * 2 to the homogeneous spin dephasing time T 2 or longer [1][2][3][4][5][6]. These periodic pulse sequences enable precision sensing and long-lived quantum states, but they come with drawbacks. They usually limit sensing to a narrow bandwidth and erase signal built up from quasistatic fields. Moreover, commuting echo pulses with gate operations makes decoupling during multi-qubit gates a nontrivial task [7].Continuous dynamical decoupling (CDD) offers an alternative method for prolonging T * 2 that can be used when the limitations of PDD become too restrictive. NV center CDD protocols forego the standard Zeeman spin state basis {(m s =) + 1, 0, −1} in favor of an engineered basis in which the "dressed" eigenstates are less sensitive to environmental noise than the bare spin states [8][9][10][11][12][13][14][15][16]. For an NV center spin qubit, magnetic field fluctuations from nearby paramagnetic impurities and instabilities in a magnetic bias field typically dominate dephasing. A qubit composed of dressed states designed to be more robust to these fluctuations could have a prolonged T * 2 and could be used for precision sensing of quasi-static, nonmagnetic fields such as temperature [17] or strain. For quantum information processing, CDD allows decoupling to continue during gate operations, thus protecting both...

Optomechanical Quantum Control of a Nitrogen-Vacancy Center in Diamond

“…Note that earlier experimental studies on mechanical coupling of NV centers have used exclusively electron-phonon interactions in the ground-state triplet of the NV centers [5][6][7][8][11][12][13]. The ground-state electron-phonon coupling, however, is about six orders of magnitude weaker than the excited-state electron-phonon coupling due to the symmetry of the relevant wave functions [37,38].…”

“…There has also been strong recent interest in using acoustic or mechanical waves, in particular surface acoustic waves (SAWs), for quantum control and on-chip quantum communication of artificial atoms. Experimental and theoretical efforts have included coherent coupling of SAWs or mechanical vibrations to superconducting qubits [1][2][3], SAW-based universal quantum transducers [4], strain-mediated coupling between a mechanical resonator and artificial atoms such as nitrogen vacancy (NV) centers in diamond and semiconductor quantum dots (QDs) [5][6][7][8][9][10][11][12], mechanical quantum control of electron spins in diamond [13,14], phononic QED [4,15], and phonon-mediated spin squeezing [16].…”

Coupling a Surface Acoustic Wave to an Electron Spin in Diamond via a Dark State

“…Applications for phonon cooling and lasing have also been considered theoretically [7,8]. In addition to superconducting qubits [1,9,10], epitaxially grown as well as gate-defined quantum dots and, more recently, nitrogen vacancy (NV) centers in diamond have also been coupled to mechanical vibrations, including SAWs or mechanical modes of nanomechanical resonators [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Generation of macroscopic Schrödinger cat state in diamond mechanical resonator

“…Meantime, the hybrid system consisting of a high-Q single-crystal diamond mechanical resonator (DMR) and embedded NV centers may provide a promising platform and open up a new perspective towards achieving quantum control and studying significant quantum optics or novel quantum phenomena111213141516171819202122. In these systems, the embedded NV centers are highly susceptible to deformations of the surrounding lattice, where the strain field is robust against the dephasing or heating of the environment1213.…”

“…In these systems, the embedded NV centers are highly susceptible to deformations of the surrounding lattice, where the strain field is robust against the dephasing or heating of the environment1213. Applying this direct strain coupling mechanism, previous investigations have been focused on the mechanical spin driving12131415, enhancement of the coherence time of the NV center16, spin squeezing17, phonon cooling and lasing18.…”