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 ($T_2$). 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 $T_2 \sim$ 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.
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.
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.
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.
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.
Quantum sensing affects many fields of science, both fundamental and applied, since a high spatial resolution in combination with high sensitivities enables closeup investigation of interesting phenomena via for example spin-wave measurements [1]. One example quantum sensor that offers a high resolution due to its atomic size and works under ambient conditions is the nitrogen-vacancy (NV) centre. Two quantum resources separate quantum sensing from classical sensing: coherence and entanglement. The former is already basic in many known detection protocols. However, the latter has so far not been used efficiently with any quantum sensor. This is an indication of the major challenge ahead, but the potential result is a significant enhancement of the sensitivity, further increasing the possibilities with quantum sensors.