Nitrogen-vacancy Centers Research Articles

Probing coherence properties of shallow implanted NV snsembles under different oxygen terminations

Abstract Nitrogen vacancy (NV) color centers in diamond have shown great potential for various applications in quantum technology due to their long coherence times, high sensitivity to magnetic fields and atomic scale resolution. However, one major challenge in utilizing near surface NV centers is the decoherence caused by spins and charges fluctuating on the surface, which affects the spin properties of the sensors. To reduce the induced noise, various oxygen surface treatments such as low power oxygen plasma treatment and annealing under oxygen atmosphere have been explored to terminate the diamond surface and reduce its impact on NV coherence. We showed that the NV center's coherence time can be enhanced up to a factor of 3 over a large spectral range of noise. Double electron electron resonance (DEER) measurements revealed an extra source of decoherence, scaling similarly as the P1 spin bath. The improvement in coherence times is accompanied with an increase in measured ketone/ether content and reduction of sp2 signal in X-ray photoelectron spectroscopy (XPS) measurements. Finally we compared the performance of different NV ensembles and surface treatments for sensing external proton spins. The oxygen annealing is an effective procedure of enhancing the spin coherence times and reducing broad band spin noise experienced by shallow implanted ensemble NV centers in diamond.

Entanglement structures in disordered chains of nitrogen-vacancy centers

Entanglement structures in disordered chains of nitrogen-vacancy centers

Abstract B033: Towards magnetic resonance microscopy for liquid biopsy in cancer therapy monitoring

Abstract The advancement of liquid biopsy techniques promises to revolutionize cancer diagnostics and therapy monitoring, by offering a minimally invasive approach to track tumor progression and treatment efficacy. One central issue preventing advancements are innovations in sensor technology, necessary to enable the detection of molecular and cellular biomarkers with sufficient precision. Over the past decade, atomic-scale quantum sensors have emerged as powerful detectors, offering the ability to perform precise measurements of temperature, pressure, and magnetic fields on the single cell scale. These sensors, based on the interaction of spin qubits with their environment, have the unique capability to amplify and exploit environmental interactions for highly accurate detection, making them ideal for complex biological applications. In this context, we present an advanced quantum sensing platform specifically tailored for liquid biopsy applications in cancer therapy monitoring. This platform integrates the capabilities of optical microscopy with magnetic resonance imaging (MRI) techniques, utilizing nitrogen-vacancy (NV) centers in diamond as quantum sensors by converting magnetic resonance signals into optical signals, which are subsequently captured by a high-speed camera. Our platform offers a novel approach, promising quantitative analysis of single cancer cells from liquid samples with unprecedented accuracy. Unlike traditional MRI, our method captures signals over a wide field of view directly in real space. Each camera pixel records a magnetic resonance spectrum, providing detailed multicomponent information about the sample, such as molecular concentration, diffusion, and relaxation behavior, which are critical for understanding the tumor’s microenvironment. Our quantum sensing technology holds significant potential for enhancing the sensitivity of liquid biopsies. By capturing detailed molecular information from blood or other body fluids, it will enable in-depth analysis of Circulating Tumor Cells (CTCs), circulating tumor DNA (ctDNA), exosomes, and other biomarkers. Citation Format: Karl D. Briegel, Robin D. Allert, Dominik B. Bucher, Julia D. Draeger, Nick R v. Grafenstein, Linyan Nie. Towards magnetic resonance microscopy for liquid biopsy in cancer therapy monitoring [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B033.

Deep-neural-network-based magnetic-field acquisition method for quantum sensing with nitrogen-vacancy centers

Deep-neural-network-based magnetic-field acquisition method for quantum sensing with nitrogen-vacancy centers

Interferometry of quantum correlation functions to access quasiprobability distribution of work

AbstractThe Kirkwood-Dirac quasiprobability distribution, intimately connected with the quantum correlation function of two observables measured at distinct times, is becoming increasingly relevant for fundamental physics and quantum technologies. This quasiprobability distribution can take non-positive values, and its experimental reconstruction becomes challenging when expectation values of incompatible observables are involved. Here, we use an interferometric scheme aided by an auxiliary system to reconstruct the Kirkwood-Dirac quasiprobability distribution. We experimentally demonstrate this scheme in an electron-nuclear spin system associated with a nitrogen-vacancy center in diamond. By measuring the characteristic function, we reconstruct the quasiprobability distribution of work and analyze the behavior of its first and second moments. Our results clarify the physical meaning of the work quasiprobability distribution in the context of quantum thermodynamics. Finally, we study the uncertainty of measuring the Hamiltonian of the system at two times, via the Robertson-Schrödinger uncertainty relation, for different initial states.

Cavity-assisted resonance fluorescence from a nitrogen-vacancy center in diamond

The nitrogen-vacancy center in diamond is an attractive resource for the generation of remote entangled states owing to its optically addressable and long-lived electronic spin. However, its low native fraction of coherent photon emission, ~3%, undermines the achievable spin-photon entanglement rates. Here, we couple a nitrogen-vacancy center with a narrow extrinsically-broadened linewidth (159 MHz), hosted in a micron-thin membrane, to an open microcavity. The resulting Purcell factor of ~1.8 increases the zero-phonon line fraction to over 44%. Operation in the Purcell regime, together with an efficient collection of the zero-phonon-line photons, allows resonance fluorescence to be detected for the first time without any temporal filtering. We achieve a >10 signal-to-laser background ratio. This selective enhancement of the center’s zero-phonon transitions could increase spin-spin entanglement success probabilities beyond an order of magnitude compared to state-of-the-art implementations, and enable powerful quantum optics techniques such as wave-packet shaping or all-optical spin manipulation.

Atom-Vacancy-Defect-Derived Electric Hysteresis Loops and Stochastic Low-Frequency Noises in Few-Atom Layer MoS2.

Atom-vacancy-defects present in various materials yield numerous interesting physical phenomena, even obstructing high performance in some cases. On the other hand, their valuable applications to novel devices, such as nitrogen vacancy centers in diamond for quantum bits, have gathered significant attention. In particular, these tendencies become more substantial in two-dimensional (2D) (atomically) thin van der Waals layers. However, correlations with various kinds of atom defects are still under exploration. Herein, we find the stochastic behaviors of large hysteresis loops with strong photoresponse in the static electrical properties in few-atom layer semiconductors, molybdenum disulfide (MoS2). The temperature dependence and transmission electron microscopy reveal that they arise from pairs of two neighboring in-plane S-vacancy defects, which predominantly present only around the interface at the MoS2 flake/substrate, with activation energies ∼0.35 eV. The low-frequency (f) (LF) noise measurements clarify a high f shift in the two 1/f2-dependent regimes, implying stochastic behaviors of electric charges through the S-vacancy pairs with high-speed charge(spin) transitions across low kinetic energy barriers between narrow discrete states. The shallow energy sates are formed from the highly uniform S-vacancy pairs interacting with Mo atoms, which act like quantum dots. The observed stochastic operation holds promise for various application, particularly for probabilistic neuromorphic computation in artificial intelligence.

Detection of electron paramagnetic resonance of two electron spins using a single NV center in diamond

An interacting spin system is an excellent testbed for fundamental quantum physics and applications in quantum sensing and quantum simulation. For these investigations, detailed information on the interactions, e.g., the number of spins and their interaction strengths, is often required. In this study, we present the identification and characterization of a single nitrogen vacancy (NV) center coupled to two electron spins. In the experiment, we first identify a well-isolated single NV center and characterize its spin decoherence time. Then, we perform NV-detected electron paramagnetic resonance (EPR) spectroscopy to detect surrounding electron spins. From the analysis of the NV-EPR signal, we precisely determine the number of detected spins and their interaction strengths. Moreover, the spectral analysis indicates that the candidates of the detected spins are diamond surface spins. This study demonstrates a promising approach for the identification and characterization of an interacting spin system for realizing entangled sensing using electron spin as quantum reporters.

Probing Abrikosov vortices in niobium with single nitrogen-vacancy centers in nanodiamonds

Abrikosov vortices play a fundamental role in the magnetic and electric properties of superconductors. The study of their pinning forces is essential to better understand the stability of vortex lattices, with the aim of increasing critical currents in superconductors. However, the study of vortices is challenging because of their nanometric sizes and the large variation in the pinning forces. In this Letter, we use a single nitrogen-vacancy center in a nanodiamond as a nanoscale magneto sensor to locally probe single vortices and their pinning effects in a thin niobium film. This simple, far-field optical approach also offers the possibility of manipulating a single spin with a single flux quantum.

Qubit teleportation between a memory-compatible photonic time-bin qubit and a solid-state quantum network node

We report on a quantum interface linking a diamond NV center quantum network node and 795nm photonic time-bin qubits compatible with Thulium and Rubidium quantum memories. The interface makes use of two-stage low-noise quantum frequency conversion and waveform shaping to match temporal and spectral photon profiles. Two-photon quantum interference shows high indistinguishability between converted 795nm photons and the native NV center photons. We use the interface to demonstrate quantum teleportation including real-time feedforward from an unbiased set of 795nm photonic qubit input states to the NV center spin qubit, achieving a teleportation fidelity well above the classical bound. This proof-of-concept experiment shows the feasibility of interconnecting different quantum network hardware.

Robust sensing via the standard deviation with a quantum sensor

Quantum sensing has a bright future for applications in need of impeccable sensitivities. The study of periodic fields has resulted in various techniques, which deal with the limited coherence time of the quantum sensor in several ways. However, the periodic signal to measure could include forms of randomness as well, such as changes in phase or in frequency. In such cases, long measurement times required to detect the smallest of field amplitudes hamper the effectiveness of conventional techniques. In this paper, we propose and explore a robust sensing technique to combat this problem. For the technique, instead of measuring the signal amplitude directly, we measure another global property of the signal, in this case the standard deviation. This results in a much-improved sensitivity. We analyze the advantages and limitations of this technique, and we demonstrate the working with a measurement using a nitrogen-vacancy center. This work encourages scouting measurements of alternative statistics.

An instructional lab apparatus for quantum experiments with single nitrogen-vacancy centers in diamond

Hands-on experimental experience with quantum systems in the undergraduate physics curriculum provides students with a deeper understanding of quantum physics and equips them for the fast-growing quantum science industry. Here, we present an experimental apparatus for performing quantum experiments with single nitrogen-vacancy (NV) centers in diamond. This apparatus is capable of basic experiments such as single-qubit initialization, rotation, and measurement, as well as more advanced experiments investigating electron–nuclear spin interactions. We describe the basic physics of the NV center and give examples of potential experiments that can be performed with this apparatus. We also discuss the options and inherent trade-offs associated with the choice of diamond samples and hardware. The apparatus described here enables students to write their own experimental control and data analysis software from scratch, all within a single semester of a typical lab course, as well as to inspect the optical components and inner workings of the apparatus. We hope that this work can serve as a standalone resource for any institution that would like to integrate a quantum instructional lab into its undergraduate physics and engineering curriculum.

Two types of stimulated emission in HPHT diamond with a high concentration of NV centers

The paper presents the results of experimental observation of two types of stimulated emission (SE) under pulsed laser pumping at 532 nm in diamond with NV centers. A comprehensive spectroscopic characterization of multisectorial HPHT diamond plate was performed. At low pumping power, the stimulated emission from NV¯ centers was recorded as a broad (≥80 nm wide) band with a maximum at 706 nm in the {111} and {311} sectors of the diamond plate. As the pump power increased in the {111} sector, narrow-band stimulated emission (<10 nm wide) was detected, with a maximum at 716 nm and a luminescence impulse duration of 1.5–3 ns. As the pump density increased, a fine structure in the spectrum of narrow-band stimulated emission was revealed for the first time. The concentration of NV¯ centers in the {111} and {311} growth sectors was ≈10 ppm. However, there were considerable differences in the concentrations of C (35 and 3.5 ppm) and C+ centers (6.1 and 3.2 ppm, respectively). It was demonstrated that the presence of a high concentration of NV¯ centers is not the only necessary condition for the initiation of narrow-band SE in the 710–720 nm range. In the {311} sector, lighting at 360, 405, and 488 nm reduced the concentration of NV¯ centers by 15 % while increasing the concentration of C+ centers in the {311} sector. This effect is weak in the {111} sector. The authors suggested a model for narrow-band SE at the transition Valence Band → C+ with charge-state conversion of C↔C+ and NV0↔NV¯ centers. Further research on the dynamic processes is required in order to a detailed understanding of the operation of NV centers in diamond during SE generation.

Guest Editorial: Quantum Computing: A Beacon of Transformation for the Oil and Gas Industry

This past June, the United Nations proclaimed 2025 as the International Year of Quantum Science and Technology to recognize the potential of quantum science to drive innovations in sustainable development and global communications. It is also a recognition of how far the theoretical concept of quantum computing has come to become a reality, and the race to build a powerful quantum computer is accelerating every year. According to a recent report from Global Quantum Intelligence, the impact of quantum tech across the oil and gas industry could equate to $2.6 trillion by 2035. As the first chief data scientist in the oil and gas industry, I am acutely aware of the myriad challenges that our industry faces. I firmly believe that quantum computing and related quantum technologies are on the brink of revolutionizing our industry in ways we have yet to fully comprehend. The quantum revolution demands that the oil and gas and the broader energy industry rethink their approach to exponential technology and sustainability. The industry's history of adopting emerging technologies, as evidenced by the slow uptake of digital transformation, underscores the urgency of this shift. Even 30 years after the introduction of the digital oilfield concept, the industry lags in data quality, addressing data silos, and data democratization, as compared with other complex and highly regulated industries. The urgency of an energy transition towards a sustainable future necessitates the oil and gas industry to confront its complex challenges, which are beyond the scope of current computing power. Quantum computing, with its unparalleled computational power, emerges as one of the most promising technologies to optimize and accelerate solutions to the industry's intricate problems. As we discuss quantum computing in detail, we will explore how related quantum interconnected areas—quantum sensing, quantum networking, and quantum simulations—will enable unique applications for the oil and gas industry. In simple words, quantum computing is the field of computing that uses the principles of quantum mechanics to solve complex problems that are intractable for classical computers. The three main principles of quantum mechanics that are the cornerstone of quantum computing are superposition, entanglement, and quantum interference. Unlike traditional computing, where a bit (0 or 1) is the basic unit, a qubit is the unit of quantum computing. A qubit can exist in a state of 0, 1, or both simultaneously due to superposition, enabling parallel computations and the exploration of multiple solutions at once. Entanglement allows for correlated states, enabling operations on multiple qubits simultaneously for enhanced computational power. Quantum interference allows quantum states to interfere constructively or destructively with each other, amplifying correct solutions and suppressing incorrect ones, thereby empowering efficient computations. Thus, a significant quantum advantage is gained by using quantum computing for certain computationally challenging problems compared with traditional computing. Quantum computing will be performed on quantum computers, which are developed today using various technologies such as photonics, light particles, trapped ions, neutral atom traps, superconducting qubits, and controlling nitrogen vacancy centers in imperfect diamonds.

Coherent Driving of a Single Nitrogen Vacancy Center by a Resonant Magnetic Tunnel Junction.

Nitrogen vacancy (NV) centers, atomic spin defects in diamond, represent an active contender for advancing transformative quantum information science (QIS) and innovations. One of the major challenges for designing NV-based hybrid systems for QIS applications results from the difficulty of realizing local control of individual NV spin qubits in a scalable and energy-efficient way. To address this bottleneck, we introduce magnetic tunnel junction (MTJ) devices to establish coherent driving of an NV center by a resonant MTJ with voltage controlled magnetic anisotropy. We show that the oscillating magnetic stray field produced by a resonant micromagnet can be utilized to effectively modify and drive NV spin rotations when the NV frequency matches the corresponding resonance conditions of the MTJ. Our results present a new pathway to achieve all-electric control of an NV spin qubit with reduced power consumption and improved solid-state scalability for implementing cutting-edge QIS technological applications.

High‐Resolution Thermal Sensing Using Temperature‐Sensitive Cathodoluminescence Spectroscopy in Nitrogen‐Doped Nanodiamonds

The evolution of the cathodoluminescence spectra from commercially available nanodiamonds with high density of nitrogen‐vacancy defects has been studied in a large wavelength range, from 200 to 800 nm, and temperatures from 5 to 300 K, in order to achieve a temperature probe with high spatial resolution. The full width at half maximum of the peak associated to the neutral charge state of the NV center has been found to evolve with temperature in a predictable way, although its value may vary from sample to sample. We have attributed this shift to the differences in the nanodiamonds surface chemistry.

Simultaneously Detecting the Power and Temperature of a Microwave Sensor via the Quantum Technique

This study introduces a novel method for the simultaneous detection of microwave sensor power and temperature, leveraging nitrogen-vacancy (NV) centers as a robust quantum system. Through precise measurement of the optical detection magnetic resonance contrast in NV centers, the microwave power is accurately determined. Furthermore, the temperature of the sensor is obtained by monitoring the variations in zero-field splitting and thorough spectral analysis. This method enables the efficient real-time acquisition of synchronized data on both microwave power and temperature from the sensor, facilitating concurrent monitoring without the necessity of additional sensing devices. Finally, we verified that the magnetic sensitivity of the system is approximately 1.2 nT/Hz1/2, and the temperature sensitivity is around 0.38 mK/Hz1/2. The minimum resolution of microwave power is about 20 nW. The experimental results demonstrate that this quantum measurement technique provides stable and accurate data across a wide range of microwave power and temperature conditions. These findings indicate substantial potential for this technique in advanced applications such as aerospace, medical diagnostics, and high-frequency communications. Future studies will aim to extend the industrial applicability of this method by refining quantum control techniques within NV center systems.

Utilizing the multifrequency resonances of the electron spins in diamond nitrogen-vacancy centers under strong radio frequency driving for quantum sensing

Multifrequency resonances in the pulsed-optically detected magnetic resonance (ODMR) spectra of electron spins in ensemble nitrogen-vacancy (NV) centers in diamonds are investigated under strong radio frequency (RF) driving at a MHz frequency range and weak microwave driving at a GHz frequency range in a bias static magnetic field for quantum sensing applications. First, we demonstrate that the coherent destruction of tunneling, which leads to the disappearance of the main resonance peaks, can be utilized for precise calibration of the RF amplitude. Next, we clarify the condition for enhancing the sensitivity of a DC magnetic field under strong RF driving at the RF frequency that matches the split frequency due to the hyperfine interaction between 15N nuclear spins and the NV electron spins. Our findings indicate that strong RF driving increases the sensitivity of the DC magnetic field by enhancing the ODMR contrast and reducing the linewidth. The above results contribute to certifying the quantitative accuracy of RF imaging and enhancing the sensitivity of the DC magnetic field imaging using ensemble NV centers in diamonds.

All-in-one quantum diamond microscope for sensor characterization

Ensembles of nitrogen-vacancy (NV) centers in diamond are a leading platform for sensing and imaging magnetic fields at room temperature, in part due to advances in diamond growth. An essential step to improving diamond material involves the characterization of crystal and NV-related properties, such as strain and paramagnetic impurities, which can shift and broaden the NV resonances used for sensing. Full sample characterization through wide-field imaging enables both fast and detailed feedback for growers, along with the estimation of sensing performance before use. We present a quantum diamond microscope tailored for millimeter-scale wide-field mapping of key quantum properties of NV-diamond chips, including NV ensemble photoluminescence intensity, spin-lattice relaxation time (T1), and spin-coherence lifetimes (T2 and T2*). Our design also allows for lattice stress/strain and birefringence magnitude/angle mapping, and their in situ correlation with NV properties.

Functionalized Nanodiamonds for Targeted Neuronal Electromagnetic Signal Detection.

Intracellular sensing technologies necessitate a delicate balance of spatial resolution, sensitivity, biocompatibility, and stability. While existing methods partially fulfill these criteria, none offer a comprehensive solution. Nanodiamonds (NDs) harboring nitrogen-vacancy (NV) centers have emerged as promising candidates due to their sensing capabilities under biological conditions and their ability to meet all aforementioned requirements. This study focuses on expanding the application of NDs and NV center-based sensing to neuronal contexts by investigating their functionalization and subsequent effects on three distinct cell lines relevant to neurodegenerative disease research. Our study concentrates on positioning fluorescent NDs (FNDs) with NV center point defects onto neuronal cell surfaces. Achieving this through specific antibody attachment enhances the proximity of FND to neurites, facilitating the detection of local action potentials. Targeting voltage-dependent calcium channels (Cav2.2) with biotin-streptavidin-bound antibodies enables the precise positioning of FNDs. The functionalized FNDs (f-FNDs) show increased size and zeta potential, confirming the antibody presence without compromising cell viability. Two-color confocal imaging and co-localization algorithms are employed to further attest to the success of the functionalization. The f-FNDs are applied to cell cultures of three cell lines: SH-SY5Y, differentiated dopaminergic neurons, and hippocampal rat neurons; their biocompatibility and effects on synaptic activity are explored. Moreover, preliminary total internal reflection fluorescence - optically detected magnetic resonance (TIRF-ODMR) experiments across cellular sites demonstrate the magnetic field sensitivity of our sensor network. The successful establishment of this sensor network provides a platform for characterizing neuronal signaling in healthy models and conditions mimicking Parkinson's disease.