Quantum technologies promise secure communication networks and powerful new forms of information processing, but building these systems at scale remains a major challenge. Diamond is an especially attractive material for quantum devices because it can host atomic-scale defects that emit single photons and store quantum information with exceptional stability. However, fabricating the optical structures needed to control light in diamond typically relies on slow, bespoke processes that are difficult to scale. In this work, we introduce a manufacturing approach that brings diamond quantum photonics closer to industrial production. Instead of sequentially defining each device by lithography written directly on diamond, we fabricate high-precision silicon masks using commercial semiconductor foundries and transfer them onto diamond via microtransfer printing. These masks define large arrays of nanoscale optical structures, shifting the most demanding pattern-definition steps away from the diamond substrate, improving uniformity, yield, and throughput. Using this method, we demonstrate hundreds of diamond "quantum microchiplets" with improved optical performance and controlled interaction with quantum emitters. The chiplet format allows defective devices to be replaced and enables integration with existing photonic and electronic circuits. Our results show that high-quality diamond quantum devices can be produced using scalable, foundry-compatible techniques. This approach provides a practical pathway toward large-scale quantum photonic systems and hybrid quantum-classical technologies built on established semiconductor manufacturing infrastructure.
Quantum technologies promise secure communication networks and powerful new forms of information processing, but building these systems at scale remains a major challenge. Diamond is an especially attractive material for quantum devices because it can host atomic-scale defects that emit single photons and store quantum information with exceptional stability. However, fabricating the optical structures needed to control light in diamond typically relies on slow, bespoke processes that are difficult to scale. In this work, we introduce a manufacturing approach that brings diamond quantum photonics closer to industrial production. Instead of sequentially defining each device by lithography written directly on diamond, we fabricate high-precision silicon masks using commercial semiconductor foundries and transfer them onto diamond via microtransfer printing. These masks define large arrays of nanoscale optical structures, shifting the most demanding pattern-definition steps away from the diamond substrate, improving uniformity, yield, and throughput. Using this method, we demonstrate hundreds of diamond "quantum microchiplets" with improved optical performance and controlled interaction with quantum emitters. The chiplet format allows defective devices to be replaced and enables integration with existing photonic and electronic circuits. Our results show that high-quality diamond quantum devices can be produced using scalable, foundry-compatible techniques. This approach provides a practical pathway toward large-scale quantum photonic systems and hybrid quantum-classical technologies built on established semiconductor manufacturing infrastructure.
Diamond has emerged as a leading host material for solid-state quantum emitters, quantum memories, and quantum sensors. However, the challenges in fabricating photonic devices in diamond have limited its potential for use in quantum technologies. While various hybrid integration approaches have been developed for coupling diamond color centers with photonic devices defined in a heterogeneous material, these methods suffer from either large insertion loss at the material interface or evanescent light-matter coupling. Here, we present a new technique that enables the deterministic assembly of diamond color centers in a silicon nitride photonic circuit. Using this technique, we observe Purcell enhancement of silicon vacancy centers coupled to a silicon nitride ring resonator. Our hybrid integration approach has the potential for achieving the maximum possible light-matter interaction strength while maintaining low insertion loss and paves the way toward scalable manufacturing of large-scale quantum photonic circuits integrated with high-quality quantum emitters and spins.
Many quantum networking applications require efficient photonic interfaces to quantum memories which can be produced at scale and with high yield. Synthetic diamond offers unique potential for the implementation of this technology as it hosts color centers which retain coherent optical interfaces and long spin coherence times in nanophotonic structures. Here, we report a technique enabling wafer-scale processing of thin-film diamond that combines ion implantation and membrane liftoff, high-quality overgrowth, targeted color center implantation, and serial, high-throughput thermocompression bonding with yields approaching unity. The deterministic deposition of thin diamond membranes onto semiconductor substrates facilitates consistent integration of photonic crystal cavities with silicon-vacancy (SiV) quantum memories. We demonstrate reliable, strong coupling of SiVs to photons with cooperativities approaching 50. Furthermore, we show that photonic crystal cavities can be reliably fabricated across several membranes bonded to the same handling chip. Our platform enables modular fabrication where the photonic layer can be integrated with functionalized substrates featuring electronic control lines such as coplanar waveguides for microwave delivery. Finally, we implement passive optical packaging with sub-decibel insertion loss. Together, these advances pave the way to the scalable assembly of optically addressable quantum memory arrays which are a key building block for modular photonic quantum interconnects.
Abstract The nitrogen-vacancy (NV) centre in diamond is a premier solid-state defect for quantum information processing and metrology. An integrated diamond quantum device harnesses the collective properties of multiple NV centres, enabling room-temperature quantum computing and sensing. While large-scale devices are poised to fill an important gap in the burgeoning quantum technology landscape, their practical realisation has not been achieved using current top-down fabrication techniques such as ion implantation. Consequently, this necessitates the development of a bottom-up fabrication technique, which is scalable, deterministic, and possesses atomic-scale precision. Informed by existing methods for fabricating phosphorous defect qubits in silicon, we envision a hydrogen depassivation lithography technique for atomically-precise manufacturing of nitrogen-vacancy centres in diamond. This perspective article outlines a viable multi-step procedure for realising scalable fabrication of diamond quantum devices and identifies the key challenges in its development.
Nitrogen-vacancy (NV) centres in diamond show great promise for quantum computing, where photonic entanglement can be generated using long-lived optically-active spins [1]. A quantum processor would require a large number of interconnected NV centres, and an integrated platform becomes necessary for control and routing. Benefits of integration include nanophotonic cavities with ultra-small mode volumes [2], multilayer electronics, and use of existing integrated quantum photonic components and architectures. Pick-and-place methods have been adopted to combine diamond microchiplets with aluminium nitride [3]. Photonic and spin properties has also been measured in nanodiamond encapsulated in optimised silicon nitride (SiNx) [4]. However, challenges remain to interface diamond with photonics in a scalable and manufacturable process. In particular, the need to identify and manipulate stochastically located emitters requires precise and time-intensive confocal microscopy.
The past decade has seen an explosion of development in new devices, modalities, and architectures for advanced sensing, computation, and communication. This growth has been driven by the massive investments of large consumer-tech companies in data-hungry domains of customer interest. As these companies develop their products and seek a competitive edge, technologies which can provide advantage across application areas by making computation cheaper, or sensors more knowledgeable, or communication faster, are attracting more interest in and outside academia. Photonics, or the study of how to manipulate light, is a broad-based platform that inherently delivers on these promises. Although photonics has been a part of daily life since the invention of the laser, modern needs and aspirational designs which meet those needs far exceed the capabilities of the platforms which have traditionally constituted the photonics toolkit.\nThere are two specific areas where standard photonic materials are lacking - support for visible wavelengths and functionality for quantum optics. Currently, there are many implementations of systems which use visible light or quantum optics on the tabletop, but the drive to scale these technologies and deliver them to the consumer encounters a roadblock in their size and cost. Visible light sensors, for instance, could greatly benefit from conversion into an integrated photonics platform, where the optical components are printed onto a small substrate. However, the standard materials used for such systems (silicon and indium phosphide) absorb visible light, and other materials (like silicon nitride) do not have the attributes required for advanced functionality. More compellingly, there exist very few material platforms which can host the quantum defects required for next-generation technologies like quantum computation or secure communication.\nThe past decade has seen extensive research into an emerging material platform which can deliver on the ability to bring integrated visible photonics and quantum optics to the same chip - diamond. With a broad transparency region (from UV to the far infrared) and high refractive index, diamond makes an excellent material for run-of-the-mill photonic devices. More importantly, it harbors atom-like defects in its crystal lattice - the nitrogen-vacancy, silicon-vacancy, and germanium-vacancy centers, among many more - which provide a direct interface between the photons circulating within the diamond device and the quantum world. Taken together, these simple properties of diamond constitute a powerful approach towards implementation of advanced quantum technologies, such as repeaters for secure quantum communication or even, one day, computers.\nBefore that future arrives, diamond's capability must first be developed. Diamond has only been available in significant quantities for research use for about a decade, and as such, the processing technologies which are taken for granted in silicon or silicon nitride-based work must be redeveloped. Within the context of photonic devices, we discuss different fabrication strategies and their implications for device design. For visible light devices especially, we investigate methods to reduce sidewall roughness for etched structures.\nInterfacing with diamond photonic structures also brings its own unique set of challenges due to its high refractive index and very small material footprint. To this end, we develop a method termed "loaded tapered-fiber coupling" to optically access large, free-standing diamond devices. For size-limited diamond resonators and waveguides, we also develop auxiliary optical waveguides to act as spot-converters for visible wavelengths, an improvement on previous techniques for telecom-range wavelengths.\nFinally, by synthesizing these improvements in fabrication, we embark on a set of experiments in diamond microresonators. Nonlinear optics is an excellent testbed for such improvements, both for diamond's superlative properties in that regard and their high sensitivity to improvements in fabrication. First, we look at a process known as Raman lasing by constructing long path-length resonators.This technique involves the shifting of an input photon by 40 THz via the interaction with the diamond's crystal lattice.The first demonstration in a diamond integrated device was shown with a pump wavelength of 1600 nm, with an output that was tuned over 100 nm and a low threshold. Leveraging the developments in visible photonics for diamond, a second Raman laser was demonstrated, this time at near-visible (720 nm) wavelengths.This too had a Stokes output which was tunable to over 100 nm and a very low threshold. Raman-specific effects such as polarization conversion were also investigated.\nA cousin to the Raman effect, the Kerr nonlinearity plays a key role in so-called microresonator (or Kerr) frequency combs. We survey the possibilities and difficulties in implementation for a diamond platform, highlighting the competition between the Kerr and Raman nonlinearities. Although the outlook for a technologically relevant Kerr comb in diamond is ultimately pessimistic, avenues for improvement are highlighted. Namely, we investigate via simulation a related class of effects, known as supercontinuum generation.Taking advantage of subtleties of the Raman process in diamond, we can find a preferred geometry which enables generation of a broadband light spectrum natively in diamond.\nFinally, we look at alternative applications of diamond, particularly in high-power systems. Due to its excellent thermal conductivity and power-handling capacity, optics fashioned purely out of diamond can show significant advantages compared to other materials. We end with a discussion of the design principles and results stemming from this work.
Hybrid photonic quantum computers, combining stationary matter qubits and flying photonic qubits, offer an intrinsically networked and resource-efficient route to large-scale, error-corrected quantum computation. Their core components are cavity-coupled matter qubits that act as light--matter interfaces, enabling: high-efficiency on-demand single-photon generation, stable near-unity photon indistinguishability and spin--multi-photon entanglement. Semiconductor quantum dots in microcavities are a leading platform for realizing such devices. Yet reaching the performance, reproducibility and spin-coherence thresholds for large-scale error correction remains a major challenge requiring industrial fabrication and control. Here we report thousands of monolithic semiconductor quantum-dot devices fabricated using a III--V pilot production-line process compatible with large-scale deployment. Systematic control of source parameters yields state-of-the-art efficiency and supports a path to optical losses below fault-tolerance thresholds. Using field-quadrature state reconstruction as a stringent joint test of efficiency and indistinguishability, we observe near-unity photon quantum purity stable over tens of minutes and a record single-photon Wigner-function negativity. We further demonstrate seven-partite spin--multi-photon entanglement and spin coherence extendable to microsecond timescales in the low-magnetic-field regime. Finally, photons from distant sources are as indistinguishable as photons emitted successively by a single source. These results establish foundry-compatible III--V quantum dots as a scalable platform for hybrid photonic quantum computing.