Optically addressable spin defects hosted in two-dimensional van der Waals materials represent a new frontier for quantum technologies, promising to lead to a new class of ultrathin quantum sensors and simulators. Recently, hexagonal boron nitride (hBN) has been shown to host several types of optically addressable spin defects, thus offering a unique opportunity to utilise various spin species in a single material. Here we demonstrate the co-existence of two separate spin species within a single hBN powder sample, namely boron vacancy defects and visible emitter spins. To identify the two spin species, we studied photoluminescence (PL) and optically detected magnetic resonance (ODMR) spectra for the as-received commercially sourced hBN powder and after electron irradiation. Further, we prepared a film of hBN powder on a test magnetic sample (a patterned CoFeB film with in-plane magnetization) and used the hBN spins to spatially map the sample’s stray magnetic field at room temperature.Our results establish hBN as a versatile platform for quantum technologies in a van der Waals host at room temperature.
Controlling and manipulating individual quantum systems underpins the development of scalable quantum technologies. Hexagonal boron nitride (hBN) is emerging as an exceptional platform for applications in quantum photonics. The two-dimensional van der Waals (vdW) crystal hosts single photon emitting defects (quantum emitters) opening new functionality currently inaccessibly with other 3D quantum sources. Due to the two-dimensional nature of the crystal, hBN is an ideal material to integrate into vdW heterostructure devices. These devices have recently been shown to enable electrical modulation of single photon emission. Additionally, the study of the dephasing mechanisms of these sources helps assess the future utilization of hBN emitters in quantum interference experiments.
Layered van der Waals materials are emerging as compelling two-dimensional platforms for nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Amongst these, hexagonal boron nitride (hBN) is known to host ultra-bright, room temperature quantum emitters, whose nature is yet to be fully understood. Here we present a summary of the recent advances in our group on controlling and engineering the quantum emission energies in hBN as well as demonstration of using these emitters for various quantum applications. First, we show a CVD technique to grow hBN hosting high density of emitters with emission energies distributed over 20nm range. This is a milestone on continuing the hBN progress in quantum optics as uncontrollable emission wavelength hinders the potential development of hBN-based devices and applications. In addition, we report our recent understanding of photophysical properties and level structure of hBN emitters. In this regard we show a new modality for super resolution imaging based on quantum emitters in hBN which is expandable to other systems. Our findings expand current understanding of quantum emitters in hBN and demonstrate the potential of hBN for the development of hybrid quantum nanophotonic and optoelectronic devices based on two-dimensional materials.
In this work we couple bright room-temperature single-photon emission from a hexagonal boron nitride atomic defect into a laser-written photonic chip. We perform single photon state manipulation with evanescently coupled waveguides acting as a multiple beam splitter, and generate a superposition state maintaining single photon purity. We demonstrate that such states can be utilized for quantum random number generation.
Quantum optical information systems offer the potential for secure communication and fast quantum computation. To fully characterise a quantum optical system one has to use quantum tomography.1 The integration of quantum optics onto photonic chips provides advantages such as miniaturisation and stability, significantly improving quantum tomography using both re-configurable, and more recently, simpler static designs. These on-chip designs have, so far, only used probabilistic single photon sources. Here we are working towards quantum tomography using a true deterministic source - an InGaAs quantum dot.
Color centers in diamond—especially group IV defects—have been advanced as a viable solid-state platform for quantum photonics and information technologies. We investigate the photodynamics and characteristics of germanium-vacancy (GeV) centers hosted in high-pressure high-temperature diamond nanocrystals. Through back-focal plane imaging, we analyze the far-field radiation pattern of the investigated emitters and derive a crossed-dipole emission, which is strongly aligned along one axis. We use this information in combination with lifetime measurements to extract the decay rate statistics of the GeV emitters and determine their quantum efficiency, which we estimated to be ∼ ( 22 ± 2 ) % . Our results offer further insight into the photodynamic properties of the GeV center in nanodiamonds and confirm its suitability as a desirable system for quantum technologies.
The fundamental study and realisation of practical devices for quantum nanophotonic systems stems from the development of hybridised devices, consisting of a single photon source and various other constituents, which aid in controlling light-matter interactions. Emitters hosted within hexagonal boron nitride (hBN) are such a source favoured for this role, owing to its high quantum efficiency, brightness, and robustness. In our work, we explore and demonstrate the integration of hBN emitters with plasmonics, in two distinct arrangements – gold nanospheres, and a gold plasmonic nanocavity array. The former involves the utilisation of an atomic force microscope (AFM) tip to precisely position gold nanospheres to within close proximity to the quantum emitters and observe the resulting emission enhancement and fluorescence lifetime reduction. A fluorescence enhancement of over 300% and a saturated count rate in excess of 5M counts/sec is achieved, emphasising the potential of this material for hybridisation. The latter arrangement involves the direct transfer of a gold plasmonic lattice on top of an emitter hosted within hBN, similarly, to achieve emission enhancement as well as a reduction in fluorescence lifetime and provides an approach for achieving scalable, integrated hybrid systems based on low-loss plasmonic nanoparticle arrays. Both these systems give promising solutions for future employment of quantum emitters in hBN for integrated nanophotonic devices and provide us insight into the complex photodynamics, which envelop the emitters hosted within the material.
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