Nitrogen vacancy (NV) centers have been demonstrated as a useful tool in high pressure environments. However, the geometry and small working area of the diamond anvil cells (DACs) used to apply pressure present a challenge to effective delivery of microwave (mw) fields. We designed and characterized a novel slotted design for mw transmission to nitrogen-vacancy centers (NVs) in a diamond anvil cell via zero-field and in-field optically detected magnetic resonance (ODMR) measurements across pressures between 1 and 48 GPa. The mw fields experienced by NVs across the diamond culet was calculated from Rabi frequency and found to be higher and more uniform than those generated by an equivalent simple mw line, which will improve performance for wide-field, high-pressure measurements to probe spatial variations across samples under pressure.
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5 page main text, 7 page supplement, 4 figure main text, 13 figure supplement
Nitrogen vacancy (NV) centers have been demonstrated as a useful tool in high pressure environments. However, the geometry and small working area of the diamond anvil cells (DACs) used to apply pressure present a challenge to effective delivery of microwave (mw) fields. We designed and characterized a novel slotted design for mw transmission to nitrogen-vacancy centers (NVs) in a diamond anvil cell via zero-field and in-field optically detected magnetic resonance (ODMR) measurements across pressures between 1 and 48 GPa. The mw fields experienced by NVs across the diamond culet was calculated from Rabi frequency and found to be higher and more uniform than those generated by an equivalent simple mw line, which will improve performance for wide-field, high-pressure measurements to probe spatial variations across samples under pressure.
The diamond anvil cell-based high-pressure technique is a unique tool for creating new states of matter and for understanding the physics underlying some exotic phenomena. In situ sensing of spin and charge properties under high pressure is crucially important but remains technically challenging. While the nitrogen-vacancy (NV) center in diamond is a promising quantum sensor under extreme conditions, its spin dynamics and the quantum control of its spin states under high pressure remain elusive. In this study, we demonstrate coherent control, spin relaxation, and spin dephasing measurements for ensemble NV centers up to 32.8 GPa. With this in situ quantum sensor, we investigate the pressure-induced magnetic phase transition of a micron-size permanent magnet Nd 2 Fe 14B sample in a diamond anvil cell, with a spatial resolution of ∼2 μm, and sensitivity of ∼20 μT/Hz 1/2. This scheme could be generalized to measure other parameters such as temperature, pressure and their gradients under extreme conditions. This will be beneficial for frontier research of condensed matter physics and geophysics.
Nitrogen-Vacancy (NV) centers in diamond are attractive tools for sensing and quantum information. Realization of this potential requires effective tools for controlling the spin degree of freedom by microwave (mw) magnetic fields. In this work, we present a planar microwave resonator optimized for microwave-optical double resonance experiments on single NV centers in diamond. It consists of a piece of wide microstrip line, which is symmetrically connected to two 50 Ω microstrip feed lines. In the center of the resonator, an Ω-shaped loop focuses the current and the mw magnetic field. It generates a relatively homogeneous magnetic field over a volume of 0.07 × 0.1 mm3. It can be operated at 2.9 GHz in both transmission and reflection modes with bandwidths of 1000 and 400 MHz, respectively. The high power-to-magnetic field conversion efficiency allows us to produce π-pulses with a duration of 50 ns with only about 200 and 50 mW microwave power in transmission and reflection, respectively. The transmission mode also offers capability for efficient radio frequency excitation. The resonance frequency can be tuned between 1.3 and 6 GHz by adjusting the length of the resonator. This will be useful for experiments on NV-centers at higher external magnetic fields and on different types of optically active spin centers.
Nitrogen-Vacancy (NV) centers in diamond have been established as exceptionally versatile probes for quantum technologies from sensing to simulation.Owing to the versatility of diamond fabrication, NVs can be integrated into probes with nanoscale resolution and superb sensitivity.\nHowever, because the diamond is host to many other types of defects, the local environment of the NV is unique for each NV, which poses challenges for any devices instrumenting NVs.\nThis thesis contributes to the future of NV technologies along two essential directions.\nFirst, we work towards a more complete understanding of the local charge and strain environments of the NV.\nIn addition to permitting the calibration of these effects for NV probes, we suggest potential uses for the local charges and strain that had previously been considered hindrances.\nSecond, we develop new technologies for NV sensing and simulation.\nOur work integrating NVs into diamond anvil cells opens the door to detecting high pressure phenomena using the NVs as all-in-one sensors.\nFinally, our study of the coherence regimes of the local defect environment of the NV is a step towards versatile quantum simulation in dimensions lower than three.
When high static pressure is applied to a material, the arrangement of its atoms and electrons can dramatically change to allow higher density, thus leading to the creation of new phases or modifying electronic and magnetic properties of solids. Pressures of tens of kilobars (gigapascals) or even megabars can be achieved in laboratories using Diamond Anvil Cells (DACs), at the expense of working with samples of minute size. Recent studies have claimed to have uncovered materials, super-hydrides, retaining superconductivity close to room temperature under extreme pressure conditions. However, performing reliable measurements of the hallmarks of superconductivity on these samples synthesized at high-pressure is remarkably challenging, sometimes leading to controversial results. In this thesis, we chose to pursue the development of a new high-pressure optical magnetic measurement method based on the adaptation of a mature quantum technology to the DAC: Nitrogen-Vacancy (NV) centers of diamond. We fabricate ensembles of these color centers inside the tip of a diamond anvil, using them as local quantum magnetic probes based on their spin-dependent photoluminescence properties. We show that NV centers can be used to spatially map the Meissner effect in the presence of a cuprate superconductor at high pressure and record the sample's critical temperature evolution with pressure up to 31 GPa. We then systematically study the NV centers' magnetic sensing capabilities at high pressure, identifying non-hydrostatic anvil stress as a limitation above 40 to 50 GPa. Finally, we propose an anvil micro-structuring strategy lifting this constraint and enabling efficient NV magnetometry at least up to 130 GPa, paving the way toward a future settlement of the super-hydride dispute by this new diagnosis method.
Nitrogen vacancy (NV) centers in diamond have precipitated profound advances in microwave detection, manifesting themselves both in spatial resolution and sensitivity. However, typical methods based on Rabi oscillations are subject to detunings due to thermal and magnetic fluctuations and/or gradients, which introduce systematic errors and render the measurements susceptible to environmental perturbations. Here, we propose and demonstrate a novel approach for determining both the magnitude and direction of microwaves, by exploiting the spectral line broadening effect in the optically detected magnetic resonance of NV centers. This method eliminates the requirement of aligning the MW frequency to the spin transitions and is therefore immune to variations and inhomogeneities of the magnetic field and temperature, providing an optimal tool for fast imaging applications. With this method, we achieved wide-field imaging of near field microwaves generated with a microscale Ω-pattern antenna with a resolution of 800\,nm. Combining with the vector detection using multi-axis NVs, a full reconstruction of the vector microwave fields is obtained. Besides, our scheme also exhibits excellent linearity over a broad range of MW amplitudes, and the scale is theoretically calculated to be more than four orders. Our results augment the applicability of diamond-based microwave devices in applications under complex scenarios, especially where large dynamic range, fast test speed, and high spatial resolution are demanded.
For quantum sensing based on nitrogen-vacancies (NV) ensembles, microwave antennas can couple the microwave field to the NV center, which leads it to becoming the core of spin manipulation and can directly affect the sensitivity of quantum sensing. The double split-ring resonator is a widely used microwave device for NV ensembles due to the advantages of high radiation efficiency and uniform magnetic field in millimeter-scale areas. But the bandwidth (30 MHz) is quite narrow which limits the application in quantum sensing with NV ensembles. Here, we experimentally achieve continuous tuning of the resonant frequency of the double split-ring resonator by changing the copper sheet position on the edge of the outer ring. The frequency tuning range can reach 80 MHz, up to 2-3 times the bandwidth, which can cover the transition of the electron spin under different magnetic field conditions. The performance of the tunable antenna in the quantum operation of NV centers is verified by optically detected magnetic resonance and Rabi oscillation. This tunable antenna is promising in the fabrication of integrated and arrayed quantum sensors based on NV ensembles.