Sensitivity Optimization for NV-Diamond Magnetometry

Abstract

Solid-state spin systems including nitrogen-vacancy (NV) centers in diamond constitute an increasingly favored quantum sensing platform. However, present NV ensemble devices exhibit sensitivities orders of magnitude away from theoretical limits. The sensitivity shortfall both handicaps existing implementations and curtails the envisioned application space. This review analyzes present and proposed approaches to enhance the sensitivity of broadband ensemble-NV-diamond magnetometers. Improvements to the spin dephasing time, the readout fidelity, and the host diamond material properties are identified as the most promising avenues and are investigated extensively. Our analysis of sensitivity optimization establishes a foundation to stimulate development of new techniques for enhancing solid-state sensor performance.

Free-space confocal magneto-optical spectroscopies at milliKelvin temperatures

“…Spin relaxometry and spin coherence measurements require a combination of optical, microwave, and readout pulses that must be optimized to realize useful SNRs without inducing excess heating. Defects with triplet ground states and a corresponding intersystem crossing relaxation pathways only require an off-resonant 532 nm excitation for spin state initialization and readout 43 . On the other hand, defects with spin-orbit selection rules require excitation pulses resonant with the spin state to be initialized or readout 15,44 .…”

Cavity quantum electrodynamic readout of a solid-state spin sensor

“…As a natural diamond, the sample displays substantial strain and exhibits an inhomogeneous dephasing time T * 2 of 40 ns. The P1 centers (as interrogated via EPR) exhibit a full-width-half-maximum linewidth of 910 kHz, of which approximately 300 kHz can be attributed to broadening from 13 C spins [6]. The residual 610 kHz linewidth suggests an approximate total nitrogen concentration [N T ]=18 ppm [48], while integration of the P1 EPR signal suggests [N 0 s ] = 22 ppm.…”

“…Quantum devices employing optically active solid-state spin systems promise broad utility [1][2][3][4][5], but are plagued by poor quantum state readout [6]. Conventional spin readout via optical excitation and fluorescence detection destroys the information stored by a spin defect with only a few scattered photons.…”

“…Moreover, spin fluorescence contrast (i.e., the normalized difference in signal from the qubit states) is far below unity, which further reduces the quantum information that conventional readout can extract from a given spin. Hence, quantum sensors employing solid-state spin ensembles with conventional optical readout exhibit sensitivities far worse than the spin-projection noise limit, with readout fidelities F 1 limited by shot noise on the detected fluorescence [6]. Here F = 1 characterizes a measurement at the spin-projection noise limit, and 1/F denotes the measurement uncertainty relative to that limit.…”

Quantifying the performance of multi-pulse quantum sensing

“…The collapses correspond to the overlapping signals of multiple nuclear spins in the spin bath, whose product leads to coherence disappear [39,40]. The SNR of NMR is an important index and can be directly characterized by the depth of collapses [41,42]. With the optimized composite pulses, the SNR remained constant over a large recorded parameter range.…”