Composite-pulse magnetometry with a solid-state quantum sensor

Abstract

The sensitivity of quantum magnetometer is challenged by control errors and, especially in the solid state, by their short coherence times. Refocusing techniques can overcome these limitations and improve the sensitivity to periodic fields, but they come at the cost of reduced bandwidth and cannot be applied to sense static or aperiodic fields. Here we experimentally demonstrate that continuous driving of the sensor spin by a composite pulse known as rotary-echo yields a flexible magnetometry scheme, mitigating both driving power imperfections and decoherence. A suitable choice of rotary-echo parameters compensates for different scenarios of noise strength and origin. The method can be applied to nanoscale sensing in variable environments or to realize noise spectroscopy. In a room-temperature implementation, based on a single electronic spin in diamond, composite-pulse magnetometry provides a tunable trade-off between sensitivities in the mTHz À 1/2 range, comparable with those obtained with Ramsey spectroscopy, and coherence times approaching T 1 .

Decay of the rotary echoes for the spin of a nitrogen-vacancy center in diamond

“…In order to get rid of this negative correction, one can choose τ to satisfy sin 1 2 τ ω 2 + λ 2 /2 = 0, or T h 2 + A 2 0 = 2πk in dimensional units. 58 Note that the obvious conflict between this choice and the best decoupling condition Eq. (31) is insignificant, and the latter condition can be neglected.…”

“…Influence of the relevant dilute dipolar-coupled spin bath on the NV spin can be modelled as a random time-varying magnetic field obeying the statistics of the Ornstein-Uhlenbeck process (stationary Gaussian Markovian process). 11,47,49,50,61,62 Previous studies of the rotary echo decay of the NV spin, 48,49,58 while providing important insights, were restricted to low orders of the cumulant expansion of the evolution operator, or to the case of static bath. Our study avoids these limitation.…”

“…25,[39][40][41][42][43][44][45][46] At the same time, an alternative approach based on the continuous dynamical decoupling has been extensively investigated. 11,[47][48][49][50][51][52][53][54][55][56][57][58] Within this approach, strong resonant driving is applied to the NV center. The resulting fast Rabi oscillations of the NV spin, similarly to the flip-flops induced by the decoupling pulses, average out the interaction with the environment, and significantly extend the spin coherence time.…”

“…Robustness of the continuous decoupling with respect to these experimental imperfections can be greatly improved by periodically inverting the driving field (switching the driving field phase by 180 • ). 48,49,[58][59][60] The resulting signal demonstrates a series of so-called rotary echoes, which decay much slower than the regular Rabi oscillations, and may be utilized for precise nanoscale sensing. 48,49,58 Although the rotary echo protocol requires constant driving of the NV spin, and therefore much larger dissipated power, it has an additional advantage over the pulse-based dynamical decoupling: an experimentalist can independently control both the strength of driving and the driving reversal time.…”

Precision-guaranteed quantum metrology

“…The method consisting of Steps from 1 ′ to 3 ′ is exactly same as experiments for observing interference fringes in quantum metrology [13,33,34]. The precision of estimating f depends on the way of sampling φs and the choice of estimator for f .…”