Polarization- and frequency-tunable microwave circuit for selective excitation of nitrogen-vacancy spins in diamond

Abstract

We report on a planar microwave resonator providing arbitrarily polarized oscillating magnetic fields that enable selective excitation of the electronic spins of nitrogen-vacancy (NV) centers in diamond. The polarization plane is parallel to the surface of diamond, which makes the resonator fully compatible with (111)-oriented diamond. The field distribution is spatially uniform in a circular area with a diameter of 4 mm, and a near-perfect circular polarization is achieved. We also demonstrate that the original resonance frequency of 2.8 GHz can be varied in the range of 2−3.2 GHz by introducing varactor diodes that serve as variable capacitors.In recent years, the nitrogen-vacancy (NV) center in diamond has emerged as a promising platform for quantum information processing and nanoscale metrology. 1-7At the heart of both technologies lies an exquisite control of the NV electronic spin.8 The ground state of the negatively charged NV center is an S = 1 spin triplet with the m S = ±1 sublevels lying D gs = 2.87 GHz above the m S = 0 sublevel under zero magnetic field. The external static magnetic field B dc applied parallel to the quantization axis n NV (along one of the 111 crystallographic axes) further splits the m S = ±1 levels by 2γB dc , with γ = 28 GHz/T being the gyromagnetic ratio of the NV electronic spin [see Fig. 1].Initialization, control, and readout of this three-level V system are accomplished by an optically detected magnetic resonance (ODMR) technique, in which opticalLin. pol.Cir. pol. pumping by a green (∼500 nm) laser serves to initialize and read out the NV spin and short pulses of oscillating magnetic fields B ac (∼2.87 GHz) drive it into an arbitrary quantum-mechanical superposition. In ideal magnetic resonance experiments, B ac and B dc ( n NV ) should be orthogonal, 9,10 whereas in reality the direction of B ac at the location of the target NV center is hard to control or even know about. This is because a metal wire or a microfabricated stripline, commonly used for experiments with NV centers, generates B ac that is highly dependent on the positions. Moreover, B ac from these sources is linearly polarized, while the NV spin has clear transition selection rules; The m S = 0 ↔ 1 (−1) transition is driven by σ + (σ − ) circularly polarized fields. To fully exploit the S = 1 nature of the NV spin for quantum information and metrology applications, 11-14 it is highly desired to have a reliable means to generate arbitrarily polarized microwave fields.A few configurations for polarization-controlled B ac have been adopted for the NV system. A popular one is a pair of crisscrossed striplines, which generates desired fields only beneath the crossing point.15,16 A pair of parallel striplines may be a simpler alternative.17 In both examples, however, it is by design difficult or impossible to make the polarization plane perpendicular to n NV and thus to B dc .In this paper, we present a simple planar resonator circuit providing spatially uniform, arbitrarily polarized, and in-plane microwave magne...

Microstrip-line resonator with broadband, circularly polarized, uniform microwave field for nitrogen vacancy center ensembles in diamond

“…M. Mrozek et al described a circularly polarized microstrip circuit that could provide MW field with arbitrary adjusted polarization but the MW field is inhomogeneous. 17 And another circularly polarized planar MW resonator was proposed by Johannes Herrmann et al, 18 but the bandwidth of the resonator was only 60 MHz when the input return loss (S 11 ) was -10 dB. Besides, a non-circularly polarized resonator with high ARTICLE scitation.org/journal/adv homogeneity was proposed by Ning Zhang et al 14 And the resonator with an ultra-broadband (15.8 GHz) coplanar waveguide for optically detected magnetic resonance (ODMR) ensured that electron spins could be manipulated under external magnetic field up to 5000 G. 19 Both the loop-gap resonator used by D. Suter et al 20 and the two-port MW resonator used by David D. Awschalom et al 21 can provide non-circularly polarized MW field with high homogeneity.…”

Magnetic Field Imaging of Superparamagnetic Particles Using High‐Density, Perfectly Oriented NV Centers in Diamond CVD Film

“…The phase shifter in Figure (a) is to tune the depth of two dips in the ODMR spectrum, providing proper phase shift to the microwave. Without the phase shifter, the depth of the left and right dips substantially differ, likely due to the deviation from the microwave linear polarization, which need to be adjusted by the phase shifter.…”

Optimized Planar Microwave Antenna for Nitrogen Vacancy Center Based Sensing Applications

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