Temperature and spin-state dependence of phonon-limited spin relaxation for nitrogen-vacancy centers in diamond

Abstract

Phonon-induced relaxation within the nitrogen-vacancy (NV) center's electronic ground-state spin triplet limits its coherence times, and thereby impacts its performance in quantum applications. We report measurements of the relaxation rates on the NV center's |ms = 0 ↔ |ms = ±1 and |ms = −1 ↔ |ms = +1 transitions as a function of temperature from 9 to 474 K in highpurity samples. Informed by ab initio calculations, we demonstrate that NV spin-phonon relaxation can be completely explained by the effect of second-order interactions with two distinct groups of quasilocalized phonons. Using a novel analytical model based on this understanding, we determine that the quasilocalized phonon groups are centered at 68.2(17) and 167(12) meV.

Engineering non-Markovianity from defect-phonon interactions

“…In this particular case, this interaction depends on the linear combination of first-order derivatives of the spin-spin interaction evaluated at equilibrium positions ( ∂H ss /∂Q λ | u i =0 ) multiplied by the linear displacements (Q λ ). Quadratic terms proportional to Q 2 λ in the normal mode expansion are neglected in this work but can be relevant for other solid-state systems [27,37,38,39]. Since the spin-spin interaction only depends on the position of defect sites, it is convenient to introduce the defect normal modes:…”

“…Because of this complexity, modeling the defect-environment interaction requires a complete numerical approach. For instance, the SDF for diamond-based devices with molecular defects is generally obtained from molecular dynamics [13] or ab initio calculations [27]. In the case of identical harmonic oscillators (without defects) with a non-uniform distribution of elastic constants, a standard procedure is to calculate the SDF using the Langevin approach [28].…”

Estimating the degree of non-Markovianity using variational quantum circuits

“…For the case of AD, as time evolves the length of the Bloch vector becomes smaller than 1 and after sufficiently long time the vector decays to the ground state |0⟩ recovering its full length. This type of decoherence is also known as longitudinal relaxation which plays a fundamental role in color centers in diamond such as nitrogen-vacancy center coupled to lattice vibrations [38,39], and superconducting qubits in circuit QED [40].…”