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High-efficiency Posture Pre-alignment Method for Large Component Assembly via iGPS and Laser Ranging
摘要： A model for controlling the two-dimensional distribution of negatively charged nitrogen-vacancy (NV?) fluorescent centers near the surface of a diamond crystal is presented, using only a microwave plasma-assisted chemical vapor deposition (CVD) method. In this approach, a CVD diamond layer is homoepitaxialy grown via microwave plasma-assisted CVD using an isotopically enriched methane (12CH4 ), hydrogen (H2 ), and nitrogen (N2 ) gas mixture on patterned diamond (0 0 1). When the surface is imaged by means of confocal microscope photoluminescence mapping, fine grooves are observed to have been generated artificially on the diamond surface. NV? centers are found to be distributed selectively into these grooves. These results demonstrate an effective means for the formation of NV? centers of selectable size and density via microwave plasma-assisted CVD, with potential application in the production of diamond quantum sensors.
关键词： doping,nitrogen-vacancy centers,homoepitaxial,groove structure,Diamond,microwave plasma-assisted chemical vapor deposition
更新于2025-09-16 10:30:52
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-limited sensing of static magnetic fields via fast rotation of quantum spins
摘要： Diamond-based quantum magnetometers are more sensitive to oscillating (ac) magnetic fields than static (dc) fields because the crystal impurity-induced ensemble dephasing time T ? 2 , the relevant sensing time for a dc field, is much shorter than the spin coherence time T2, which determines the sensitivity to ac fields. Here we demonstrate measurement of dc magnetic fields using a physically rotating ensemble of nitrogen-vacancy centers at a precision ultimately limited by T2 rather than T ? 2 . The rotation period of the diamond is comparable to T2 and the angle between the nitrogen-vacancy (NV) axis and the target magnetic field changes as a function of time, thus upconverting the static magnetic field to an oscillating field in the physically rotating frame. Using spin-echo interferometry of the rotating NV centers, we are able to perform measurements for over 100 times longer compared to a conventional Ramsey experiment. With modifications our scheme could realize dc sensitivities equivalent to demonstrated NV center ac magnetic field sensitivities of order 0.1 nT Hz?1/2.
关键词： spin-echo interferometry,nitrogen-vacancy centers,T2-limited sensing,dc magnetic fields,quantum magnetometers
更新于2025-09-10 09:29:36
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Single-photon heralded two-qubit unitary gates for pairs of nitrogen-vacancy centers in diamond
摘要： The implementation of a high-fidelity two-qubit quantum logic gate remains an outstanding challenge for isolated solid-state qubits such as nitrogen-vacancy (NV) centers in diamond. In this work, we show that by driving pairs of NV centers to undergo photon scattering processes that flip their qubit states simultaneously, we can achieve a unitary two-qubit gate conditioned upon a single photon-detection event. Further, by exploiting quantum interference between the optical transitions of the NV centers’ electronic states, we realize the existence of two special drive frequencies: a “magic” point where the spin-preserving elastic scattering rates are suppressed and a “balanced” point where the state-flipping scattering rates are equal. We analyzed four different gate operation schemes that utilize these two special drive frequencies, and various combinations of polarizations in the drive and collection paths. Our theoretical and numerical calculations show that the gate fidelity can be as high as 98%. The proposed unitary gate, combined with available single-qubit unitary operations, forms a universal gate set for quantum computing.
关键词： photon scattering,quantum computing,nitrogen-vacancy centers,two-qubit gate,quantum interference
更新于2025-09-09 09:28:46
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Influence of Dynamical Decoupling Sequences with Finite-Width Pulses on Quantum Sensing for AC Magnetometry
摘要： Dynamical decoupling sequences with multiple pulses can be considered to exhibit filter functions for the time evolution of a qubit superposition state. They contribute to the increase of coherence time and qubit-phase accumulation due to a time-varying field and can thus be used to achieve high-frequency-resolution spectroscopy. Such behaviors find useful application in highly sensitive detection based on qubits for various external fields, such as a magnetic field. Hence, decoupling sequences are indispensable tools for quantum sensing. In this study, we experimentally and theoretically investigate the effects of finite-width pulses in the sequences on ac magnetometry using nitrogen-vacancy centers in an isotopically controlled diamond. We reveal that the finite pulse widths cause a deviation of the optimum time to acquire the largest phase accumulation due to the sensing field from that expected by filter functions ignoring the pulse widths, even if the widths are considerably shorter than the time period of the sensing field. Moreover, we experimentally demonstrate that the deviation can be corrected by an appropriate time-frequency conversion. Our results provide a guideline for the detection of an ac field with an accurate frequency and linewidth in quantum sensing with multiple-pulse sequences.
关键词： nitrogen-vacancy centers,quantum sensing,dynamical decoupling,ac magnetometry,finite-width pulses
更新于2025-09-09 09:28:46