High-fidelity spin measurement on the nitrogen-vacancy center

Abstract

Nitrogen-vacancy (NV) centers in diamond are versatile candidates for many quantum information processing tasks, ranging from quantum imaging and sensing through to quantum communication and fault-tolerant quantum computers. Critical to almost every potential application is an efficient mechanism for the high fidelity readout of the state of the electronic and nuclear spins. Typically such readout has been achieved through an optically resonant fluorescence measurement, but the presence of decay through a meta-stable state will limit its efficiency to the order of 99%. While this is good enough for many applications, it is insufficient for large scale quantum networks and fault-tolerant computational tasks. Here we explore an alternative approach based on dipole induced transparency (state-dependent reflection) in an NV center cavity QED system, using the most recent knowledge of the NV center's parameters to determine its feasibility, including the decay channels through the meta-stable subspace and photon ionization. We find that single-shot measurements above fault-tolerant thresholds should be available in the strong coupling regime for a wide range of cavity-center cooperativities, using a majority voting approach utilizing single photon detection. Furthermore, extremely high fidelity measurements are possible using weak optical pulses.

First principles predictions of magneto-optical data for semiconductor point defect identification: the case of divacancy defects in 4H–SiC

“…The physics of semiconductor point defects is of outstanding importance for controlling their optical and electrical properties [1,2].The study of point defect properties is a field of much active interest due to recent discoveries of numerous magnetically and optically active defect centers that can act as a single photon source [3][4][5][6][7] or a quantum bit (qubit) [8][9][10]. So far, the most thoroughly investigated point defect for use in qubits are the NV-center in diamond [11][12][13][14][15][16], phosphor in silicon [17][18][19] and divacancy [20][21][22] in silicon carbide (SiC). Furthermore, numerous other centers in various semiconducting host materials are proposed as potential magneto-optical centers, such as silicon-vacancy and germanium-vacancy centers in diamond [23,24], silicon vacancy in SiC [25,26], carbon anti-site vacancy pair in SiC [27], Ce 3+ and Pr 3+ ions in yttrium aluminum garnet [5,28], Eu and Nd 3+ ion in yttrium orthosilicate [29,30], Nd 3+ yttrium orthovanadate [31], defect spins in aluminum nitride [32], etc.…”

Cavity quantum electrodynamics with color centers in diamond

“…Fabry-Perotstyle cavities offer compatibility with bulk-like defects, making them suitable for use with NV centers in currently available materials [114]. Moreover, their very high quality factors > 10 6 allow linewidths smaller than the fine structure splittings of the NV center, enabling the spin-selective cavity enhancement employed in proposed protocols for qubit readout and quantum networks [10,259,260]. Finally, cavity mirrors formed on the tips of optical fibers couple directly to propagating fiber modes, simplifying outcoupling.…”

“…5). Furthermore, the narrow cavity linewidths afforded by open cavities offer an opportunity for spin-selective enhancement, opening the door for high fidelity spin measurement [259], as well as schemes for quantum communication, computation, and metrology [10,260,261]. Finally, while scaling to multi-cavity systems remains an active area of research [262], progress in parallelized open-cavity fabrication techniques [222] shows the potential for larger-scale technologies.…”

Decoding Quantum Error Correction Codes With Local Variation

“…This variability will not be the result of any changing external influence, but inherent in the information content associated with the measurement outcomes themselves. Any multishot [42] or long-time count-threshold [43] measurement scheme in the presence of error is expected to display such local variation. We perform pseudothreshold simulations for the repetition and surface codes, comparing the standard, fixed-error-rate phenomenological error model with the case for an error-rate drawn from a discrete, balanced, two-component distribution D of equal mean p μ but a fixed relative width σ…”