Magnetic nanoparticles have wide applications in various fields, e.g., magnetic recording in information science, magnetic resonance imaging, and magnetic therapy in bio-medicine. In this chapter, we will review recent applications of magnetic nanoparticles or magnetic complexes in the cutting-edge field of quantum sensing, especially in hybrid quantum sensing. Quantum sensing is a quantum technology for ultrasensitive detection, which is particularly useful for sensing weak signals at the nanoscale. The quantum systems that offer unprecedented sensitivity, resolution, and/or flexibility include superconducting qubits, defect centers in solids, atomic vapors, cold atoms, and so on. Usually, they have spin properties and possess excellent magnetic-field sensitivity; but they are insensitive to temperature, electric field, pressure, etc., and even immune to some bio-parameters (e.g., pH and glucose concentration). Recently, hybrid quantum sensing has offered new possibilities. By converting the insensitive or immune parameters into magnetic signals, the range of detectable parameters of quantum sensing can be broadened significantly. In this chapter, we first give a brief introduction to diamond quantum sensing, then review the applications of magnetic nanoparticles or magnetic complexes in diamond quantum sensing and nano-magnetism, and finally, discuss the potential applications and challenges for hybrid diamond quantum sensing.
Magnetic nanoparticles have wide applications in various fields, e.g., magnetic recording in information science, magnetic resonance imaging, and magnetic therapy in bio-medicine. In this chapter, we will review recent applications of magnetic nanoparticles or magnetic complexes in the cutting-edge field of quantum sensing, especially in hybrid quantum sensing. Quantum sensing is a quantum technology for ultrasensitive detection, which is particularly useful for sensing weak signals at the nanoscale. The quantum systems that offer unprecedented sensitivity, resolution, and/or flexibility include superconducting qubits, defect centers in solids, atomic vapors, cold atoms, and so on. Usually, they have spin properties and possess excellent magnetic-field sensitivity; but they are insensitive to temperature, electric field, pressure, etc., and even immune to some bio-parameters (e.g., pH and glucose concentration). Recently, hybrid quantum sensing has offered new possibilities. By converting the insensitive or immune parameters into magnetic signals, the range of detectable parameters of quantum sensing can be broadened significantly. In this chapter, we first give a brief introduction to diamond quantum sensing, then review the applications of magnetic nanoparticles or magnetic complexes in diamond quantum sensing and nano-magnetism, and finally, discuss the potential applications and challenges for hybrid diamond quantum sensing.
Quantum sensing is a quantum technology for ultrasensitive detection, which is particularly useful for sensing weak signals at the nanoscale. Nitrogen vacancy centers in diamond, thanks to their superb quantum coherence under ambient conditions and the stability of the material in extreme and complicated environments, have been demonstrated as promising quantum probes in multi-parameter sensing. Their spin properties make them particularly sensitive to magnetic fields, but they are insensitive to temperature, electric field, pressure, etc., and even immune to some bio-parameters (e.g., pH and glucose concentration). Recently, hybrid quantum sensing has emerged as a promising avenue for further enhancing the capabilities of diamond sensors. Different techniques can potentially improve the sensitivity, range of detectable parameters, and sensing frequencies of diamond sensors. This review provides an overview of hybrid quantum sensing using diamond. We first give a brief introduction to quantum sensing using diamond, and then review various hybrid sensing schemes that have been developed to enhance the sensing capabilities of diamond sensors. Finally, the potential applications and challenges associated with hybrid quantum sensing in diamond are discussed.
In modern-day quantum metrology, quantum sensors are widely employed to detect weak magnetic fields or nanoscale signals. Quantum devices, exploiting quantum coherence, are inevitably connected to physical constants and can achieve accuracy, repeatability, and precision approaching fundamental limits. As a result, these sensors have shown utility in a wide range of research domains spanning both science and technology. A rapidly emerging quantum sensing platform employs atomic-scale defects in crystals. In particular, magnetometry using nitrogen-vacancy (NV) color centers in diamond has garnered increasing interest. NV systems possess a combination of remarkable properties, optical addressability, long coherence times, and biocompatibility. Sensors based on NV centers excel in spatial resolution and magnetic sensitivity. These diamond-based sensors promise comparable combination of high spatial resolution and magnetic sensitivity without cryogenic operation. The above properties of NV magnetometers promise increasingly integrated quantum measurement technology, as a result, they have been extensively developed with various protocols and find use in numerous applications spanning materials characterization, nuclear magnetic resonance (NMR), condensed matter physics, paleomagnetism, neuroscience and living systems biology, and industrial vector magnetometry. In this chapter, NV centers are explored for magnetic sensing in a number of contexts. In general, we introduce novel regimes for magnetic-field probes with NV ensembles. Specifically, NV centers are developed for sensitive magnetometers for applications where microwaves (MWs) are prohibitively invasive and operations need to be carried out under zero ambient magnetic field. The primary goal of our discussion is to improve the utility of these NV center-based magnetometers.
Quantum sensors encompass a diverse class of devices that exploit quantum coherence to detect weak or nanoscale signals. As their behavior is tied to physical constants, quantum sensors can achieve accuracy, repeatability, and precision approaching fundamental limits [1, 2]. As a result, these sensors have shown utility in a wide range of applications in both science and engineering leading to innovations. Among many solid-state spin systems, nitrogen-vacancy (NV) centers in diamonds have attracted considerable attention as a leading platform in many fields of quantum technologies, from quantum sensing to information processing and communication applications. They have superior physical properties, and their quantum coherence is preserved even at room temperature. The energy levels of NV centers are sensitive to magnetic fields, electric fields, strain, and temperature, and the spatial resolution is scalable from nanometers to millimeters. Therefore, diamond quantum sensors are distinctive sensors with multimodality and span scalable application fields. To realize an ideal quantum sensor for applications, the technical challenges in the sensor materials and the quantum control techniques, such as coherent microwave spin manipulation, effective optical spin-state initialization, and readout, have been developed. This chapter briefly explains the sensing principle using NV centers and then introduces sensor systems for biomedical applications, and monitoring of batteries for electric vehicles and internal power devices.
Quantum sensing using nitrogen-vacancy (NV) centers in diamond has emerged as a powerful platform for detecting ultra-low magnetic fields under ambient conditions. Owing to their long spin coherence times, optical addressability, and compatibility with aqueous environments, it has found widespread applications in biosensing and bio-imaging. This review presents the fundamental principles and recent advances in NV-based quantum magnetometry for biosensing applications, with a particular focus on measurements in aqueous medium and at cellular and molecular length scales. We discuss the underlying spin physics of NV centers and highlight two primary detection modalities: optically detected magnetic resonance (ODMR) and T1 relaxometry-based sensing and how these approaches aids in the detection of both static magnetic fields and dynamic magnetic noise arising from biological processes. The review explores key application areas, including nanoscale nuclear magnetic resonance (NMR), monitoring of neural activity, detection of abnormal or rogue cells using NV-based platforms etc. In addition, strategies for enhancing sensitivity, such as surface functionalization of nanodiamonds, femtosecond (fs) laser-written photonic structures, and integration with microfluidic and lab-on-chip systems have also been discussed in depth. We also address the critical challenges, including surface-induced decoherence, charge-state instability, and signal-to-noise limitations in biofluids associated with NV-based biosensing applications. Finally, we outline future prospects, highlighting how NV-based magnetic biosensing provides a promising pathway for translating quantum sensing technologies into practical biomedical applications.
Extreme conditions, such as ultra-low temperatures, high pressures, and strong magnetic fields, are critical to producing and studying exotic states of matter. To measure physical properties under extreme conditions, the advanced sensing schemes are required. As a promising quantum sensor, the diamond nitrogen-vacancy (NV) center can detect magnetic field, electronic field, pressure, and temperature with high sensitivity. Considering its nanoscale spatial resolution and ultra-wide working range, the diamond quantum sensing can play an important role in frontier studies involving extreme conditions. This paper reviews the spin and optical properties of diamond NV center under extreme conditions, including low temperature, high temperature, zero field, strong magnetic fields, and high pressures. The opportunities and challenges of diamond quantum sensing under extreme conditions are discussed. The basic knowledge of spin-based quantum sensing and its applications under extreme conditions are also covered.
Abstract This review provides a comprehensive overview of the key materials underpinning quantum technologies, including two-dimensional system (2D), superconducting materials, and nitrogen-vacancy (NV − ) centers in diamond. Particular emphasis is placed on their roles in quantum sensing, communication, and qubit design. Quantum sensors, such as atomic vapor magnetometers, solid-state spin sensors, and superconducting quantum interference devices (SQUID) circuits, have become essential tools for measuring magnetic fields and detecting physical phenomena at extremely small scales. These technologies, with diverse applications ranging from medicine and geophysics to biotechnology and materials science, offer new opportunities for detecting and measuring nanoscale phenomena and are poised to play a key role in the future of quantum technologies.