Hexagonal boron nitride (hBN) has emerged as a promising two-dimensional host for stable single-photon emission owing to its wide bandgap, high photostability, and compatibility with nanophotonic integration. We present a simulation-based study of temperature-dependent spectral dynamics and optical coherence in a mechanically decoupled quantum emitter in hBN. Employing a hybrid stochastic framework that combines Ornstein--Uhlenbeck detuning fluctuations with temperature-dependent, Gaussian-distributed discrete frequency jumps, motivated by experimentally observed spectral diffusion and blinking, we reproduce the measured evolution of inhomogeneous linewidth broadening and the progressive degradation of photon coherence across the relevant cryogenic range (5-30K). The model captures phonon-related spectral diffusion with a cubic temperature dependence and the onset of jump-like spectral instabilities at higher temperatures. By calibrating the hybrid diffusion, jump parameters to the experimentally measured full width at half maximum (FWHM) of the emission line and analyzing the second-order correlation function $g^{(2)}(τ)$ under resonant driving, we establish a unified phenomenological description that links stochastic detuning dynamics to the decay of optical coherence in a resonantly driven emitter. Analysis of $g^{(2)}(τ)$ under resonant driving reveals an additional dephasing rate $γ_{\mathrm{sd+j}}$ that rises monotonically with temperature and drive strength, leading to a predicted critical crossover to overdamped dynamics at $T_{\mathrm{crit}} \approx 25.91$~K. This hybrid framework provides a quantitative connection between accessible spectroscopic observables and the dominant noise mechanisms limiting coherent optical control in mechanically decoupled quantum emitters, exemplified in hBN and generalizable to similar emitters in other materials.
Hexagonal boron nitride (hBN) is gaining interest for potential applications in integrated quantum nanophotonics. Yet, to establish hBN as an integrated photonic platform several cornerstones must be established, including the integration and coupling of quantum emitters to photonic waveguides. Supported by simulations, we study the approach of monolithic integration, which is expected to have coupling efficiencies that are 4 times higher than those of a conventional hybrid stacking strategy. We then demonstrate the fabrication of such devices from hBN and showcase the successful integration o…
Quantum emitters in hexagonal boron nitride (hBN) are emerging as bright and robust sources of single photons for applications in quantum optics. In this work we present detailed studies on the limiting factors to achieve Fourier Transform limited spectral lines. Specifically, we study phonon dephasing and spectral diffusion of quantum emitters in hBN via resonant excitation spectroscopy at cryogenic temperatures. We show that the linewidths of hBN quantum emitters are phonon broadened, even at 5K, with typical values of the order of one GHz. While spectral diffusion dominates at increasing pu…
Hexagonal Boron Nitride (hBN) mono and multilayers are promising hosts for room temperature single photon emitters (SPEs). In this work we explore high energy (~ MeV) electron irradiation as a means to generate stable SPEs in hBN. We investigate four types of exfoliated hBN flakes - namely, high purity multilayers, isotopically pure hBN, carbon rich hBN multilayers and monolayered material - and find that electron irradiation increases emitter concentrations dramatically in all samples. Furthermore, the engineered emitters are located throughout hBN flakes (not only at flake edges or grain bou…
Controlling and manipulating individual quantum systems in solids underpins the growing interest in development of scalable quantum technologies. Recently, hexagonal boron nitride has garnered significant attention in quantum photonic applications due to its ability to host optically stable quantum emitters. However, the large band gap of hBN and the lack of efficient doping inhibits electrical triggering and limits opportunities to study electrical control of emitters. Here, we show an approach to electrically modulate quantum emitters in n hBN graphene van der Waals heterostructure. We show …
Two-dimensional hexagonal boron nitride (hBN) that hosts bright room-temperature single-photon emitters (SPEs) is a promising material platform for quantum information applications. An important step towards the practical application of hBN is the on-demand, position-controlled generation of SPEs. Several strategies have been reported to achieve the deterministic creation of hBN SPEs. However, they either rely on a substrate nanopatterning procedure that is not compatible with integrated photonic devices or utilize a radiation source that might cause unpredictable damage to hBN and underlying …
Inhomogeneous broadening is a major limitation for the application of quantum emitters in hBN to integrated quantum photonics. Here we demonstrate that blue emitters with an emission wavelength of 436 nm are less sensitive to electric fields than other quantum emitter species in hBN. Our measurements of Stark shifts indicate negligible transition dipole moments for these centers with dominant quadratic stark effect. Using these results, we employed DFT calculations to identify possible point defects with small transition dipole moments, which may be the source of blue emitters in hBN.
Assembly of quantum nanophotonic systems with plasmonic resonators are important for fundamental studies of single photon sources as well as for on-chip information processing. In this work, we demonstrate controllable nanoassembly of gold nanospheres with ultra-bright quantum emitters in 2D layered hexagonal boron nitride (hBN). We utilize an atomic force microscope (AFM) tip to precisely position gold nanospheres to close proximity of the quantum emitters and observe the resulting emission enhancement and fluorescence lifetime reduction. A fluorescence enhancement of over 300% is achieved ex…
Optically active defects in 2D materials, such as hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), are an attractive class of single-photon emitters with high brightness, room-temperature operation, site-specific engineering of emitter arrays, and tunability with external strain and electric fields. In this work, we demonstrate a novel approach to precisely align and embed hBN and TMDs within background-free silicon nitride microring resonators. Through the Purcell effect, high-purity hBN emitters exhibit a cavity-enhanced spectral coupling efficiency up to $46\%$ at …
Resonant excitation of solid-state quantum emitters enables coherent control of quantum states and generation of coherent single photons, which are required for scalable quantum photonics applications. However, these systems can often decay to one or more intermediate dark states or spectrally jump, resulting in the lack of photons on resonance. Here, we present an optical co-excitation scheme which uses a weak non-resonant laser to reduce transitions to a dark state and amplify the photoluminescence from quantum emitters in hexagonal boron nitride (hBN). Utilizing a two-laser repumping scheme…
Insights into the Nature of Quantum Emitters in Electron-Irradiated hexagonal Boron Nitride
Technical University of Munich（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Friedrich Schiller University Jena（耶拿弗里德里希·席勒大学）；Fraunhofer-Institute for Applied Optics and Precision Engineering IOF（弗劳恩霍夫应用光学和精密工程研究所）；Max Planck School of Photonics（马克斯·普朗克光子学校）；Australian National University（澳大利亚国立大学）
Correlating spin and optical properties of quantum emitters in hBN
University of Technology Sydney（悉尼科技大学）；ARC Centre of Excellence for Transformative Meta-Optical Systems（变革性超光学系统卓越研究中心）；National Institute for Materials Science（国立材料研究所）
We propose and design photonic crystal cavities (PCCs) in hexagonal boron nitride (hBN) for diverse photonic and quantum applications. Two dimensional (2D) hBN flakes contain quantum emitters which are ultra-bright and photostable at room temperature. To achieve optimal coupling of these emitters to optical resonators, fabrication of cavities from monolithic hBN is therefore required, to maximize the overlap between cavity optical modes and the emitters. Here, we design 2D and 1D PCCs using anisotropic indices of hBN. The influence of underlying substrates and material absorption are investiga…
Quantum emitters based on atomic defects in layered hexagonal Boron Nitride (hBN) have emerged as promising solid state 'artificial atoms' with atom-like photophysical and quantum optoelectronic properties. Similar to other atom-like emitters, defect-phonon coupling in hBN governs the characteristic single-photon emission and provides an opportunity to investigate the atomic and electronic structure of emitters as well as the coupling of their spin- and charge-dependent electronic states to phonons. Here, we investigate these questions using photoluminescence excitation (PLE) experiments at T=…
Hexagonal boron nitride (hBN) is gaining considerable attention as a solid-state host of quantum emitters from the ultraviolet to the near infrared spectral ranges. However, atomic structures of most of the emitters are speculative or unknown, and emitter fabrication methods typically suffer from poor reproducibility, spatial accuracy, or spectral specificity. Here, we present a robust, deterministic electron beam technique for site-specific fabrication of blue quantum emitters with a zero-phonon line at 436 nm (2.8 eV). We show that the emission intensity is proportional to electron dose and …
Layered van der Waals materials are emerging as compelling two-dimensional (2D) platforms for studies of 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 unique in that it hosts ultra-bright, room temperature single photon emitters (SPEs). However, an outstanding challenge is to locate SPEs in hBN with high precision, a task which requires breaking the optical diffraction limit. Here, we report the imaging of SPEs in layered hBN wit…
Quantum emitters in hexagonal Boron Nitride (hBN) were recently reported to hol a homogeneous linewidth according to the Fourier-Transform limit up to room temperature. This unusual observation was traced back to decoupling from in-plane phonon modes which can arise if the emitter is located between two planes of the hBN host material. In this work, we investigate the origins for the mechanical decoupling. Improved sample preparation enabled a reduced background and a 70-fold decrease of spectral diffusion which was so far the major drawback of defect center in hBN and allowed us to reveal a g…
Quantum emitters in hexagonal boron nitride (hBN) have recently emerged as promising bright single photon sources. In this letter we investigate in details their optical properties at cryogenic temperatures. In particular, we perform temperature resolved photoluminescence studies and measure photon coherence times from the hBN emitters. The obtained value of 81(1) ps translates to a width of $\sim$12 GHz which is higher than the Fourier transform limited value of $\sim$32 MHz. To account for the photodynamics of the emitter, we perform ultrafast spectral diffusion measurements that partially a…
Color centers in hexagonal boron nitride (hBN) have emerged as promising candidates for single-photon emitters (SPEs) due to their bright emission characteristics at room temperature. In contrast to mono- and few-layered hBN, color centers in multi-layered flakes show superior emission characteristics such as higher saturation counts and spectral stability. Here, we report a method for determining both the axial position and three-dimensional dipole orientation of SPEs in thick hBN flakes by tuning the photonic local density of states using vanadium dioxide (VO2), a phase change material. Emit…
Color centers in hexagonal boron nitride have shown enormous promise as single-photon sources, but a clear understanding of electron-phonon interaction dynamics is critical to their development for quantum communications or quantum simulations. We demonstrate photon antibunching in the filtered auto- and cross-correlations $g^{(2)}_{lm}(τ)$ between zero-, one- and two-phonon replicas of defect luminescence. Moreover, we combine autocorrelation measurements with a violation of the Cauchy-Schwarz inequality in the filtered cross-correlation measurements to distinguish a low quantum-efficiency de…
Quantum emitters in van der Waals (vdW) materials have attracted lots of attentions in recent years, and shown great potentials to be fabricated as quantum photonic nanodevices. Especially, the single photon emitter (SPE) in hexagonal boron nitride (hBN) emerges with the outstanding room-temperature quantum performances, whereas the ubiquitous blinking and bleaching restrict its practical applications and investigations critically. The blister in vdW materials possessing stable structure can modify the local bandgap by strains on nanoscale, which is supposed to have the ability to fix this pho…
Combining solid state single photon emitters (SPE) with nanophotonic platforms is a key goal in integrated quantum photonics. In order to realize functionality in potentially scalable elements, suitable SPEs have to be bright, stable, and widely tunable at room temperature. In this work we show that selected SPEs embedded in a few layer hexagonal boron nitride (hBN) meet these demands. In order to show the wide tunability of these SPEs we employ an AFM with a conductive tip to apply an electrostatic field to individual hBN emitters sandwiched between the tip and an indium tin oxide coated glas…
Secure Quantum Key Distribution Using a Room-Temperature Quantum Emitter
QLocked Technology Development Inc.（QLocked技术开发有限公司）；İzmir Institute of Technology（伊兹密尔理工大学）；ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology（ICFO-光子科学研究所，巴塞罗那科学技术研究院）；University of Strathclyde（斯特拉斯克莱德大学）；Humboldt-Universität zu Berlin（柏林洪堡大学）
Single-photon emitters in solid-state systems are important building blocks for scalable quantum technologies. Recently, quantum light emitters have been discovered in the wide-gap van der Waals insulator hBN. These color centers have attracted considerable attention due to their quantum performance at elevated temperatures and wide range of transition energies. Here, we demonstrate coherent state manipulation of a single hBN color center with ultrafast laser pulses and investigate in our joint experiment-theory study the coupling between the electronic system and phonons. We demonstrate that …
In recent years, mono-layers and multi-layers of hexagonal boron nitride (hBN) have been demonstrated as host materials for localized atomic defects that can be used as emitters for ultra-bright, non-classical light. The origin of the emission, however, is still subject to debate. Based on measurements of photon statistics, lifetime and polarization on selected emitters we find that these atomic defects do not act as pure single photon emitters. Our results strongly and consistently indicate that each zero phonon line of individual emitters is comprised of two independent electronic transition…
Hexagonal boron nitride (hBN) is an emerging two dimensional material for quantum photonics owing to its large bandgap and hyperbolic properties. Here we report a broad range of multicolor room temperature single photon emissions across the visible and the near infrared spectral ranges from point defects in hBN multilayers. We show that the emitters can be categorized into two general groups, but most likely possess similar crystallographic structure. We further show two approaches for engineering of the emitters using either electron beam irradiation or annealing, and characterize their photo…
Monolayer WSe$_2$ hosts bright single-photon emitters. Because of its compliance, monolayer WSe$_2$ conforms to patterned substrates without breaking, thus creating the potential for large local strain, which is one activation mechanism of its intrinsic quantum emitters. Here, we report an approach to creating spatially and spectrally isolated quantum emitters from WSe$_2$ monolayers with few or no detrimental sources of emission. We show that a bilayer of hexagonal boron nitride (hBN) and WSe$_2$ placed on a nanostructured substrate can be used to create and shape wrinkles that communicate lo…
Single photon emitters (SPEs) in low-dimensional layered materials have recently gained a large interest owing to the auspicious perspectives of integration and extreme miniaturization offered by this class of materials. However, accurate control of both the spatial location and the emission wavelength of the quantum emitters is essentially lacking to date, thus hindering further technological steps towards scalable quantum photonic devices. Here, we evidence SPEs in high purity synthetic hexagonal boron nitride (hBN) that can be activated by an electron beam at chosen locations. SPE ensembles…
