Fiber-Integrated van der Waals Quantum Sensor The cover image illustrates a fiber-integrated van der Waals quantum sensor. The circular Bragg grating cavity fabricated from hexagonal boron nitride (hBN) with optically active spin defects, is integrated with an optical fiber using a deterministic transfer technique. The fiber-integrated hBN cavity enables efficient excitation and collection of signal without the need of a confocal microscope. The fiber-based quantum sensing platform may pave the way to a new generation of robust, remote, multi-functional quantum sensors. For further details, see article number 2401987 by Je-Hyung Kim, Igor Aharonovich, and co-workers.
Fiber-Integrated van der Waals Quantum Sensor The cover image illustrates a fiber-integrated van der Waals quantum sensor. The circular Bragg grating cavity fabricated from hexagonal boron nitride (hBN) with optically active spin defects, is integrated with an optical fiber using a deterministic transfer technique. The fiber-integrated hBN cavity enables efficient excitation and collection of signal without the need of a confocal microscope. The fiber-based quantum sensing platform may pave the way to a new generation of robust, remote, multi-functional quantum sensors. For further details, see article number 2401987 by Je-Hyung Kim, Igor Aharonovich, and co-workers.
Single-photon sources are crucial components for building quantum networks and communications, but their optical coherent control remains a significant challenge in the development of quantum technologies. Recently, single-photon sources in atomically thin 2D materials such as transition metal dichalcogenides and van der Waals materials have emerged as promising solid-state quantum light emitters [1]. Hexagonal boron nitride (hBN) is a 2D insulator, which hosts optically active states in its band gap that efficiently emit single photons even at room temperature. The wide range of emission wavelengths, narrow emission lines, and convenient tunability of these hBN emitters make them particularly interesting for quantum sensing and wavelength division multiplexed quantum communications. They can also be found in commercially available nanocrystals, making them ideal for creating large arrays of single-photon emitters [2] and efficient coupling to photonic structures, such as 3D-printed microlenses [3].
Atomically thin two-dimensional materials, with their ultra-thin structure and exceptional sensitivity to the local environment, are emerging as an important platform for next-generation quantum sensing. Their van der Waals bonding and atomic thin layers allow sensing elements to be placed in extremely close proximity to target systems—often just a few atoms away. This proximity dramatically enhances interactions with local optical, mechanical, and electrostatic fields, enabling exceptionally sensitive detection with ultrahigh spatial resolution. Beyond sensitivity, the layered van der Waals architecture offers a unique opportunity to integrate multiple sensing functions into a unified platform, where sensing, signal amplification, and readout can be distributed across tailored layers rather than relying on a single sensor element. Recent advances in optically addressable spin defects in hexagonal boron nitride and excitonic and polaritonic platforms in transition-metal dichalcogenides highlight the emergence of a new generation of quantum and quantum-enhanced sensors. These sensors conform to various substrates and enable multiparameter detection. In this Perspective, we outline the principles that distinguish atomically thin quantum sensors from bulk counterparts and explore emerging opportunities and challenges in developing scalable, multifunctional 2D quantum sensing technologies.
Spin defects in two-dimensional materials hold significant potential for quantum information technologies and sensing applications. The negatively charged boron vacancy (VB-) in hexagonal boron nitride (hBN) has attracted considerable attention as a quantum sensor due to its demonstrated sensitivity to temperature, magnetic fields, and pressure.1 However, its applications have thus far been limited by inherently dim photoluminescence (PL). By fabricating a van der Waals heterostructure with a sensitizing donor layer, lead iodide (PbI2), we effectively enhance the PL intensity from the VB- by 5-45x, while maintaining compatibility with other heterostructures and vdW optoelectronic platforms. The type-I band alignment at the heterojunction enables efficient exciton migration while suppressing back-electron transfer, and the strong spectral overlap between the PbI2 emission and defect absorption supports efficient fluorescence resonance energy transfer. Ab initio density functional theory (DFT) predicts a photon-ratcheting mechanism that boosts absorption and emission while maintaining magnetic resonance (ODMR) contrast through minimal hybridization. Experimentally, the heterostructure exhibits enhanced continuous-wave ODMR sensitivity and functions as a precise probe of external magnetic fields. This work establishes a proof-of-concept for amplifying weak defect signals in nanomaterials, highlighting a new strategy for engineering their optical and magnetic responses.
Negatively charged boron vacancy (VB−) centers in hexagonal boron nitride (h-BN) have attracted wide-range interests owing to their van der Waals lattice and their potentials for in-situ quantum sensing. Here we propose and experimentally demonstrate an all-optical strategy for wide-field magnetometry based on VB− centers. This strategy exploits the magnetically sensitive ground-state level anti-crossing (GSLAC) of VB− centers, which induces a strong electron spin transition between mS=0 and mS=−1 states, enabling microwave-free magnetic field measurement. By monitoring the shift of GSLAC feature, the external magnetic field can be precisely determined. Using this technique, we demonstrate all-optical wide-field imaging of near-field DC magnetic field distribution from current-carrying circuits over an area of around 42 × 21 μm2. An estimated photon shot-noise-limited sensitivity of 67.1 μT/Hz is achieved for a single pixel, which is an approximately threefold improvement over the ODMR method, along with a spatial resolution of about 1 μm per pixel. Our approach expands the applicability of VB− centers in quantum sensing, paving the way for robust and convenient magnetometry under extreme conditions.
Quantum sensing and metrology" is a relatively new research field.However, this research field is growing rapidly because of some outstanding features that pre-existing technologies do not have.We can thus achieve sensing with extremely high sensitivity across wide dynamic ranges, such as magnetic fields and temperature, or extremely accurate measurements of factors such as gravity, time, and position using quantum sensing and metrology.Multiple sensing of magnetic fields and temperature is also one of the attractive features of quantum sensing.In addition, the information with nanometer ranges extracted in local areas can be observed using nanoparticles with quantum sensors since only one spin defect can act as a sensor.These features for quantum sensing and metrology open new doors to a wide variety of fields and, as a result, ideas for new applications beyond our present imagination.Although groundbreaking demonstrations have been previously reported (Kucsko et al., 2013;Tetienne et al., 2017;Thiel et al., 2019), it is difficult to say that technology for quantum sensing and metrology is well developed at present.The quality of host materials for spin defects that act as quantum sensors should be improved.For example, diamond is a host material for the negatively charged nitrogen-vacancy (NV) center, which is one of the most famous spin defects that acts as a quantum sensor (Balasubramanian et al., 2008).At present, there is no technology to fabricate diamond wafers of large diameters.Besides, we must develop controlling methods for reducing crystal defects, including unintentionally doped impurities, although the quality of diamond substrates improves day by day.Of course, diamond is not only a host material for spin defects but also other materials, such as silicon carbide (SiC), Gallium nitride (GaN), and hexagonal boron nitride (hBN), are expected to be applied to host materials (Ohshima et al., 2018;Gottscholl et al., 2021;Hoang, 2022), and researchers are making a significant effort to improve the quality of such materials.New host materials for spin defects as well as new spin defects themselves will be found in the future and, as a result, the applications of quantum sensing will be expanded to cover a broad range of fields.In addition, it is important to establish methodologies for introducing spin defects in host materials.So far, two major methods are applied to the introduction of such spin defects during crystal growth and energetic particle irradiation (Balasubramanian et al., 2009;Yamamoto et al., 2013).Introducing spin defects during crystal growth has an advantage from the point of view of the quality of spin defects as well as host materials since unexpected residual defects that have a harmful impact on spin defects are also introduced by irradiation.For sensing with extremely high sensitivity, spin defects with