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In this paper we study the dynamics of an ensemble of nitrogen-vacancy centers in diamond when its photoluminescence is detected by means of a widefield imaging system. We develop a seven-level model and use it to simulate the widefield detection of nitrogen-vacancy centers Rabi oscillations. The simulation results are compared with experimental measurements showing a good agreement. In particular, we use the model to explain the asymmetric shape of the detected Rabi oscillations due to an incomplete repolarization of the nitrogen-vacancy center during the pulse sequence implemented for the detection of Rabi oscillations., Comment: 14 pages, 7 figures

Engineering a layer of nitrogen-vacancy (NV) centers on the tip of a diamond anvil creates a multipurpose quantum sensors array for high pressure measurements, especially for probing magnetic and superconducting properties of materials. Expanding this concept above 100 GPa appears to be a substantial challenge. We observe that deviatoric stress on the anvil tip sets a limit at 40-50 GPa for practical magnetic measurements based on optically detected magnetic resonance (ODMR) of NV centers under pressure. We show that this limit can be circumvented up to at least 130 GPa by machining a micropillar on the anvil tip to create a quasi-hydrostatic stress environment for the NV centers. This is quantified using the pressure dependence of the diamond Raman shift, the NV ODMR dependence on applied magnetic field, and NV photoluminescence spectral shift. This paves the way for direct and reliable detection of the Meissner effect in superconductors above 100 GPa, such as super-hydrides., Comment: 5 pages, 4 figures

The spin readout of an ensemble of nitrogen-vacancy (NV) centers in diamond can be realized by a photoconductive detection that is a complementary method to the optical detection of the NV electron spin magnetic resonance. Here, we implement the photoconductive detection through graphitic planar electrodes that collect the photocurrent. Graphitic electrodes are patterned using a xenon Focused-Ion Beam on an Optical-Grade quality diamond crystal containing a nitrogen concentration of ~1 ppm and a NV concentration of a few ppb. Resistance and current-voltage characteristics of the NV-doped diamond junction are investigated tuning the 532 nm pump beam intensity. The junction has an ohmic behavior and under a strong bias field, we observe velocity saturation of the optically-induced carriers in the diamond junction. We perform the photoconductive detection in continuous-wave regime of the magnetic resonance of the NV centers ensemble for a magnetic field applied along the <100> and the <111> direction with a magnitude above 100 mT. This technique enables the realization of all-carbon diamond quantum sensors integrating graphitic microstructures for the electrical readout., Comment: 11 pages, 3 figures, the following article has been submitted to Applied Physics Letters

The fast development of radio-frequency (RF) technologies increases the need for compact, low consumption and broadband real-time RF spectral analyser. To overcome the electronic bottleneck encountered by electronic solutions, which limits the real time bandwidth to hundreds of MHz, we propose a new approach exploiting the quantum properties of the nitrogen-vacancy (NV) center in diamond. Here we describe a Quantum Diamond Signal Analyser (Q-DiSA) platform and characterize its performances. We successfully detect RF signals over a large tunable frequency range (25 GHz), a wide instantaneous bandwidth (up to 4 GHz), a MHz frequency resolution (down to 1 MHz), a ms temporal resolution and a large dynamic range (40 dB).

The Brownian motion of a particle hotter than its environment is an iconic out-of-equilibrium system. Its study provides valuable insights into nanoscale thermal effects. Notably, it supplies an excellent diagnosis of thermal effects in optically levitated particles, a promising platform for force sensing and quantum physics tests. Thus, understanding the relevant parameters in this effect is critical. In this context, we test the role of particles' shape and material, using optically levitated nanodiamonds hosting NV centers to measure the particles' internal temperature and center-of-mass dynamics. We present a model to assess the nanodiamond internal temperature from its dynamics, adaptable to other particles. We also demonstrate that other mechanisms affect the nanodiamond dynamics and its stability in the trap. Finally, our work, by showing levitating nanodiamonds as an excellent tool for studying nano-thermal effects, opens prospects for increasing the trapping stability of optically levitated particles., Comment: 14 pages with supporting information

Scanning diamond magnetometers based on the optically detected magnetic resonance of the nitrogen-vacancy centre offer very high sensitivity and non-invasive imaging capabilities when the stray fields emanating from ultrathin magnetic materials are sufficiently low (< 10 mT). Beyond this low-field regime, the optical signal quenches and a quantitative measurement is challenging. While the field-dependent NV photoluminescence can still provide qualitative information on magnetic morphology, this operation regime remains unexplored particularly for surface magnetisation larger than $\sim$ 3 mA. Here, we introduce a multi-angle reconstruction technique (MARe) that captures the full nanoscale domain morphology in all magnetic-field regimes leading to NV photoluminescence quench. To demonstrate this, we use [Ir/Co/Pt]$_{14}$ multilayer films with surface magnetisation an order of magnitude larger than previous reports. Our approach brings non-invasive nanoscale magnetic field imaging capability to the study of a wider pool of magnetic materials and phenomena.