Abstract Nitrogen-vacancy (NV) centres in diamond hold promise in quantum sensing applications. A major interest in them is an enhancement of their sensitivity by the extension of the coherence time (T2). In this report, we experimentally generated more than four dressed states in a single NV centre in diamond based on Autler-Townes splitting (ATS). We also observed the extension of the coherence time to T2 ~ 1.5 ms which is more than two orders of magnitude longer than that of the undressed states. As an example of a quantum application using these results we propose a protocol of quantum sensing, which shows more than an order of magnitude enhancement in the sensitivity.
Abstract Nitrogen-vacancy (NV) centres in diamond hold promise in quantum sensing applications. A major interest in them is an enhancement of their sensitivity by the extension of the coherence time (T2). In this report, we experimentally generated more than four dressed states in a single NV centre in diamond based on Autler-Townes splitting (ATS). We also observed the extension of the coherence time to T2 ~ 1.5 ms which is more than two orders of magnitude longer than that of the undressed states. As an example of a quantum application using these results we propose a protocol of quantum sensing, which shows more than an order of magnitude enhancement in the sensitivity.
Nitrogen-vacancy (NV) centres in diamond hold promise in quantum sensing applications. A major interest in them is an enhancement of their sensitivity by the extension of the coherence time (T2). In this report, we experimentally generated more than four dressed states in a single NV centre in diamond based on Autler-Townes splitting (ATS). We also observed the extension of the coherence time to T2∼ 1.5 ms which is more than two orders of magnitude longer than that of the undressed states. As an example of a quantum application using these results we propose a protocol of quantum sensing, which shows more than an order of magnitude enhancement in the sensitivity.
The nitrogen-vacancy (NV) centre in diamond is a perfect candidate for quantum sensing applications applied to numerous fields of science. Past studies improved the sensitivity of diamonds containing NV centres by increasing their density or prolonging their coherence time. However, few studies discussed the effects of other defects inside the diamond crystal on the sensitivity of the NV centres. In this study, we demonstrated the implication of single substitutional nitrogen defects on the fluorescence emission, charge state stability, coherence time and sensitivity of the NV centres. We found that there is an optimal concentration of nitrogen defects that allows diamond samples to have a high-density of NV centres and high fluorescence without significantly affecting the coherence time. This results will inform the correct choice of diamond characteristics for current and future quantum sensing applications with the NV centres.
The nitrogen-vacancy (NV) centre in diamond is a perfect candidate for quantum sensing applications applied to numerous fields of science. Past studies improved the sensitivity of diamonds containing NV centres by increasing their density or prolonging their coherence time. However, few studies discussed the effects of other defects inside the diamond crystal on the sensitivity of the NV centres. In this study, we demonstrated the implication of single substitutional nitrogen defects on the fluorescence emission, charge state stability, coherence time and sensitivity of the NV centres. We found that there is an optimal concentration of nitrogen defects that allows diamond samples to have a high-density of NV centres and high fluorescence without significantly affecting the coherence time. This results will inform the correct choice of diamond characteristics for current and future quantum sensing applications with the NV centres.
Because of their high sensitivity, quantum materials are extremely promising for new technologies. The main challenge lies in maintaining a sufficiently quantum coherence times for quantum computation or quantum sensing systems. NV centers in diamond which are point defects consisting of a substitutional nitrogen atom neighboring an atomic vacancy, where an electron pair can reside in a triplet state – are ideal candidates for the development of industrial-scale quantum systems. These spin states exhibit ms-long coherence times at room temperature and can be manipulated optically, hence opening interesting perspectives for sending magnetic fields with high sensitivity1.At HiQuTe Diamond, we take up the challenge of mastering the entire nitrogen-doped diamond production chain synthesized by Microwave Plasma-Assisted Chemical Vapor Deposition (MPACVD). We aim at creating affordable diamonds specially engineered to achieve long coherence times with high NV density and high doping uniformity. This quest require to overcome the impact of several external factors that contribute to electron spin decoherence. First, the chemical composition of the diamond, specifically the types and concentrations of impurities within the diamond matrix (such as substitutional nitrogen NS, NV centres, mono-vacancies and clusters, hydrogen, etc.), as well as their electrical charge states (NS⁰, NS⁺, NV⁰, NV⁻) should be carefully controlled. Thanks to extensive scientific research conducted over the past decade, combined with our own R&D efforts, we are now able to quantify these parameters using experimental techniques compatible with industrial applications (Raman and UV-Vis spectroscopy) and compare our results with key performance indicators2. Second, we study the relationship between coherence (T2*) and strain inhomogeneities in our diamond layers, which we analyse using birefringence measurements. Our findings demonstrate our capability to produce CVD diamond layers with reduced strain and extended defect and confirm that strain could be a critical limiting factor for T2*.In this poster, I will review the efforts carried out at HiQuTe Diamond to develop specific material that is well suited for quantum sensing applications.References1.Barry, J. F., Schloss, J. M., Bauch, E., Turner, M. J., Hart, C. A., Pham, L. M., & Walsworth, R. L. (2020). Sensitivity optimization for NV-diamond magnetometry. Reviews of Modern Physics, 92(1), 015004.2.Langer, J. (2022). Quantum-grade diamond for cavity-based solutions. Fraunhofer Verlag.
When the word diamond comes up, the majority of people thinks about engagement rings or gemstones. In fact, it is additionally, one of the most promising host materials for the implementation of advanced technology, exploiting the nature of quantum physics. Such quantum technologies have disruptive potential, ones the quantum effects can be applied in macroscopic, commercial products. The nitrogen-vacancy (NV) centre in diamond is a promising candidate to perform such tasks in the fields of quantum computation, quantum cryptography or metrology. Especially in the field of quantum sensing, the NV sensor impresses with nano-scale spatial resolution paired with high sensitivity. The electronic spin of the atomic-sized point defect can be initialised, manipulated and read-out at ambient conditions and coherence lifetimes are comparably long. Diamond magnetometers based on negatively charged NV centres have shown to be very attractive, and the sensitivity goes down to the single-atom level. In order to exploit such a high sensitivity level for sensing prospects, in this thesis, the NV centres are fabricated well confined in a certain distance to the diamond surface, since the detectable field usually decays with the third power of the distance between sensor and target. The surface depicts a fracture of the spin wise protecting diamond lattice and charge fluctuations affect the stability of NV centres, which are overcome by diamond surface termination. In order to improve the sensitivity further, the sensor density, measurement contrast and interaction time are increased. The nitrogen doping technique, which is applied during a plasma-enhanced chemical vapour deposition (PECVD) diamond growth process is used to fabricate NV centre ensembles aligned along one diamond crystal axis, thereby improving the measurement contrast by a factor up to four. The interaction time limiting spin bath is analysed using the sensor capabilities of the NVs, which leads to enhanced growth strategies and the fabrication of sensitivity optimised NV centre ensembles for magnetometry applications.
Quantum sensing has witnessed rapid development and transition from laboratories to practical applications in the past decade. Applications of quantum sensors, ranging from nanotechnologies to biosensing, are expected to benefit from quantum sensors' unprecedented spatial resolution and sensitivity. Solid-state spin systems are particularly attractive platforms for quantum sensing technologies because room temperature operation is viable while reaching the quantum limits of sensitivity. Among various solid-state spin systems, nitrogen-vacancy (NV) centers in diamond demonstrated high-fidelity initialization, coherent control, and high contrast readout of the electron spin state. However, electron spin coherence due to noise from the surrounding spin bath and this environment effect limits the sensitivity of NV centers. Thus, a critical task in NV center-based quantum sensing is sensitivity enhancement through coherence protection. Several strategies, such as dynamical decoupling techniques, feedback control, and nuclear spin-assisted sensing protocols, have been developed and realized for this task. Among these strategies, nuclear spin-assisted protocols have demonstrated greater enhancement of electron spin coherence. In addition, the electron and nuclear spin pair of an NV center in diamond naturally allows the application of the nuclear spin-assisted sensitivity enhancement protocol. Owing to long nuclear coherence times, further enhancement of sensitivity can be achieved by exploiting active nuclear spins (e.g., 14N, 13C) in the proximity of an NV center as memory ancillas when coupled with the NV center. Here, we review the spin properties of NV centers, mechanisms of the nuclear spin-assisted protocol and its gate variation, and the status of quantum sensing applications in high-resolution nuclear spin spectroscopy, atomic imaging, and magnetic field sensing. We discuss the potential for commercialization, current challenges in sensitivity enhancement, and conclude with future research directions for promoting the development of nuclear spin-assisted protocol and its integration into industrial applications.