No Arabic abstract
We develop a parallel optically detected magnetic resonance (PODMR) spectrometer to address, manipulate and read out an array of single nitrogen-vacancy (NV) centers in diamond in parallel. In this spectrometer, we use an array of micro-lens to generate 20 * 20 laser-spot lattice (LSL) on the objective focal plane, and then align the LSL with an array of single NV centers. The quantum states of NV centers are manipulated by a uniform microwave field from a {Omega}-shape coplanar coil. As an experimental demonstration, we observe 80 NV centers in the field of view. Among them, magnetic resonance (MR) spectrums and Rabi oscillations of 18 NV centers along the external magnetic field are measured in parallel. These results can be directly used to realize parallel quantum sensing and multiple times speedup compared with the confocal technique. Regarding the nanoscale MR technique, PODMR will be crucial for high throughput single molecular MR spectrum and imaging.
We give instructions for the construction and operation of a simple apparatus for performing optically detected magnetic resonance measurements on diamond samples containing high concentrations of nitrogen-vacancy (NV) centers. Each NV center has a spin degree of freedom that can be manipulated and monitored by a combination of visible and microwave radiation. We observe Zeeman shifts in the presence of small external magnetic fields and describe a simple method to optically measure magnetic field strengths with a spatial resolution of several microns. The activities described are suitable for use in an advanced undergraduate lab course, powerfully connecting core quantum concepts to cutting edge applications. An even simpler setup, appropriate for use in more introductory settings, is also presented.
The possibility of using Nitrogen-vacancy centers in diamonds to measure nanoscale magnetic fields with unprecedented sensitivity is one of the most significant achievements of quantum sensing. Here we present an innovative experimental set-up, showing an achieved sensitivity comparable to the state of the art ODMR protocols if the sensing volume is taken into account. The apparatus allows magnetic sensing in biological samples such as individual cells, as it is characterized by a small sensing volume and full bio-compatibility. The sensitivity at different optical powers is studied to extend this technique to the intercellular scale.
Neutral silicon vacancy (SiV0) centers in diamond are promising candidates for quantum networks because of their excellent optical properties and long spin coherence times. However, spin-dependent fluorescence in such defects has been elusive due to poor understanding of the excited state fine structure and limited off-resonant spin polarization. Here we report the realization of optically detected magnetic resonance and coherent control of SiV0 centers at cryogenic temperatures, enabled by efficient optical spin polarization via previously unreported higher-lying excited states. We assign these states as bound exciton states using group theory and density functional theory. These bound exciton states enable new control schemes for SiV0 as well as other emerging defect systems.
We report quantitative measurements of optically detected ferromagnetic resonance (ODFMR) of ferromagnetic thin films that use nitrogen-vacancy (NV) centers in diamonds to transduce FMR into a fluorescence intensity variation. To uncover the mechanism responsible for these signals, we study ODFMR as we 1) vary the separation of the NV centers from the ferromagnet (FM), 2) record the NV center longitudinal relaxation time $T_1$ during FMR, and 3) vary the material properties of the FM. Based on the results, we propose the following mechanism for ODFMR. Decay and scattering of the driven, uniform FMR mode results in spinwaves that produce fluctuating dipolar fields in a spectrum of frequencies. When the spinwave spectrum overlaps the NV center ground-state spin resonance frequencies, the dipolar fields from these resonant spinwaves relax the NV center spins, resulting in an ODFMR signal. These results lay the foundation for an approach to NV center spin relaxometry to study FM dynamics without the constraint of directly matching the NV center spin-transition frequency to the magnetic system of interest, thus enabling an alternate modality for scanned-probe magnetic microscopy that can sense ferromagnetic resonance with nanoscale resolution.
In this paper cross-relaxation between nitrogen-vacancy (NV) centers and substitutional nitrogen in a diamond crystal was studied. It was demonstrated that optically detected magnetic resonance signals (ODMR) can be used to measure these signals successfully. The ODMR were detected at axial magnetic field values around 51.2~mT in a diamond sample with a relatively high (200~ppm) nitrogen concentration. We observed transitions that involve magnetic sublevels that are split by the hyperfine interaction. Microwaves in the frequency ranges from 1.3 GHz to 1.6 GHz ($m_S=0longrightarrow m_S=-1$ NV transitions) and from 4.1 to 4.6 GHz ($m_S=0longrightarrow m_S=+1$ NV transitions) were used. To understand the cross-relaxation process in more detail and, as a result, reproduce measured signals more accurately, a model was developed that describes the microwave-initiated transitions between hyperfine levels of the NV center that are undergoing anti-crossing and are strongly mixed in the applied magnetic field. Additionally, we simulated the extent to which the microwave radiation used to induce ODMR in the NV center also induced transitions in the substitutional nitrogen via cross-relaxation. The improved understanding of the NV processes in the presence of a magnetic field will be useful for designing NV-diamond-based devices for a wide range of applications from implementation of q-bits to hyperpolarization of large molecules to various quantum technological applications such as field sensors.