In the relentless pursuit of practical quantum technologies, a critical bottleneck remains unresolved: the scalable production of reliable qubits, the elemental carriers of quantum information. Central to this challenge is the development of solid-state quantum emitters capable of generating single photons with exceptional purity and stability. Addressing this, a recent breakthrough reported by researchers at Rice University in collaboration with Oak Ridge National Laboratory and the University of Technology Sydney sets a new paradigm in quantum photonics. Their work, recently published in Science Advances, demonstrates the first low-noise, room-temperature single-photon emitters (SPEs) synthesized within carbon-doped hexagonal boron nitride (h-BN) thin films using a scalable growth technique.
Qubits, the quantum analogues of classical bits, underpin the promises of quantum computing and secure quantum communication. Unlike classical bits restricted to binary states of 0 or 1, qubits exploit superposition and entanglement, allowing simultaneous encoding of multiple states. However, harnessing such phenomena demands a photon source that can reliably emit one—and only one—photon at a time, with high purity and operational stability, especially at ambient temperatures. Single-photon emitters based on point defects or “color centers” in solid-state materials are prime candidates as these qubit sources, but their synthesis and stability have been fraught with challenges.
The team at Rice University turned their focus to hexagonal boron nitride, an atomically thin, two-dimensional crystalline material celebrated for its exceptional mechanical, thermal, and chemical stability. Historically, h-BN’s ability to host SPEs was recognized, but prior fabrication methods struggled with reproducibility, purity, and scalability. Utilizing pulsed laser deposition (PLD), a thin-film growth method granting exquisite control over deposition parameters, the researchers introduced carbon atoms directly into the h-BN lattice during synthesis. This co-deposition approach intentionally embedded defects acting as robust, stable SPEs, circumventing the need for high-temperature, post-synthesis doping processes that previously compromised emitter quality.
PLD’s compatibility with low-temperature growth regimes, coupled with its integration of doping in a single step, represents a significant advancement. By doping at the point of growth, the team established an unprecedented uniformity in defect distribution across centimeter-scale films. This innovation promises scalable production of quantum emitters essential for real-world applications, a milestone that bridges laboratory proof-of-concept devices with manufacturable quantum photonic platforms.
Comprehensive characterization studies—including photoluminescence spectroscopy and photon correlation measurements—provided compelling evidence of the emission properties. The carbon-doped h-BN films exhibited highly pure single-photon emission at room temperature, with photon antibunching signatures near the ideal limit, indicating a minimized likelihood of multi-photon events. Notably, the emitters maintained photostability under prolonged optical excitation, a critical attribute for integration into quantum circuits that demand current-level operational consistency.
The robust polarization of emitted photons further enhances the attractiveness of these SPEs for quantum information processing. Polarization control is fundamental for encoding quantum states and enabling secure quantum key distribution protocols. The experimental observations were complemented by first-principles theoretical modeling, which attributed the single-photon emission to specific carbon-induced defect complexes within the h-BN lattice. This confluence of experimental and computational insight elucidates defect structures that can act as reliable quantum light sources.
The implications of these findings extend beyond fundamental science. The ability to create SPEs in a scalable fashion paves the way for integrating quantum emitters directly onto photonic chips, potentially transforming the quantum communication infrastructure and quantum sensor technology. The synergy of scalable production, ambient-temperature operation, and superior emitter quality tackles the trifecta of obstacles hindering the deployment of quantum networks.
Lead author Arka Chatterjee emphasized that the novel synthesis route resolves long-standing issues associated with prior methods that relied heavily on thermally induced defects or complex post-growth treatments. These previous approaches often resulted in high background noise, emitter instability, and limited reproducibility—hurdles that constrained the transition from theoretical quantum devices to practical technologies.
Shengxi Huang, the principal investigator and Rice electrical engineer, highlighted the broader impact: “Our scalable, one-step carbon doping in h-BN not only produces high-performance single-photon sources but also opens new pathways to integrating quantum emitters into photonic and quantum systems that can be mass-produced, marking a watershed moment for quantum hardware development.”
This research was supported by an array of prominent funding sources including the U.S. National Science Foundation, Welch Foundation, Air Force Office of Scientific Research, Clarkson Aerospace Corporation, Office of Naval Research Global, and the Australian Research Council. Their collective investment underscores the critical strategic importance of quantum technologies for national and global technological leadership.
As quantum devices edge closer to commercial viability, materials engineering innovations like carbon-doped h-BN SPEs will play a pivotal role. The marriage of two-dimensional materials science with quantum optics is evidencing a new era in the fabrication of quantum light sources that merge scalability, purity, and operational convenience. It is a path destined to accelerate the advent of robust quantum computing, ultra-secure communications, and advanced sensing systems.
In the coming years, further research will likely focus on integrating these emitters with photonic waveguides and cavity structures to enhance light-matter interactions, augmenting emission rates and collection efficiency. Moreover, exploring additional dopant species and heterostructure configurations could unlock new degrees of control over quantum emission properties. The work from Rice University and their collaborators marks a defining stride toward these aspirations, establishing carbon-doped h-BN as a cornerstone material for next-generation quantum photonics.
Subject of Research: Scalable synthesis and characterization of high-purity single-photon emitters in carbon-doped hexagonal boron nitride thin films for quantum information technologies.
Article Title: Room-Temperature High-Purity Single Photon Emission from Carbon-Doped Boron Nitride Thin Films
News Publication Date: June 23, 2025
Web References:
References:
- Arka Chatterjee et al., Science Advances, DOI: 10.1126/sciadv.adv2899
Image Credits: Photo by Jeff Fitlow/Rice University
Keywords:
Single photon sources, Quantum computing, Qubits, Materials engineering, Thin film deposition, Pulsed laser deposition, Carbon doping, Optics, Optical properties
