The burgeoning field of nanophotonics has grown to be a major research area, primarily because of the ability to control and manipulate single quantum systems (emitters) and single photons on demand. For many years, studying nanophotonic phenomena was limited to traditional semiconductors (including silicon and GaAs) and experiments were carried out predominantly at cryogenic temperatures. In the last decade, however, diamond has emerged as a new contender to study photonic phenomena at the nanoscale. Offering a plethora of quantum emitters that are optically active at room temperature and ambient conditions, diamond has been exploited to demonstrate super‐resolution microscopy and realize entanglement, Purcell enhancement, and other quantum and classical nanophotonic effects. Elucidating the importance of diamond as a material, this progress report highlights the recent achievements in the field of diamond nanophotonics, and conveys a roadmap for future experiments and technological advancements.
The burgeoning field of nanophotonics has grown to be a major research area, primarily because of the ability to control and manipulate single quantum systems (emitters) and single photons on demand. For many years, studying nanophotonic phenomena was limited to traditional semiconductors (including silicon and GaAs) and experiments were carried out predominantly at cryogenic temperatures. In the last decade, however, diamond has emerged as a new contender to study photonic phenomena at the nanoscale. Offering a plethora of quantum emitters that are optically active at room temperature and ambient conditions, diamond has been exploited to demonstrate super‐resolution microscopy and realize entanglement, Purcell enhancement, and other quantum and classical nanophotonic effects. Elucidating the importance of diamond as a material, this progress report highlights the recent achievements in the field of diamond nanophotonics, and conveys a roadmap for future experiments and technological advancements.
The ability to control the state of individual atoms is a new challenge for science and technology in the 21st century. Currently, experiments on individual quantum systems such as trapped ions, single molecules, quantum dots, superconducting qubits and photons are crucial for the rapidly growing field of quantum information processing and communication. In general, solid state systems are preferable for scaling and the choice of material plays a crucial role; for example, in classical electronic devices continual performance enhancement and miniaturization is strongly linked to the success of silicon-based technology. For quantum applications, diamond has the potential to become the material of choice, because its large bandgap enables the control of optically active impurities and higher operation temperature. This focus issue collates original research contributions from some of the leading groups in the field as a showcase for the very latest developments in diamond-based quantum technologies.
Chapter 1 reviews recent advances towards the realization of quantum networks based on atom-like solid-state quantum emitters coupled to nanophotonic devices. Specifically, focus is on experiments involving the negatively charged silicon-vacancy color center in diamond. These emitters combine homogeneous, coherent optical transitions and a long-lived electronic spin quantum memory. Optical and spin properties of this system at cryogenic temperatures and experiments where silicon-vacancy centers are coupled to nanophotonic cavities are discussed. Finally, the chapter discusses experiments demonstrating quantum nonlinearities at the single-photon level and two-emitter entanglement in a single nanophotonic device.
Developing reliable and efficient single-photon sources is crucial for advancing quantum technologies, relying on nonlinear frequency conversion or spontaneous emission from individual quantum emitters. While different types of single-photon sources excel in specific applications, none meet all criteria for an “ideal” source: exceptional brightness, high purity, and indistinguishability. To address this challenge, coupling single-photon emitters with designer nanostructures can significantly enhance emission performance, a pivotal area in quantum nanophotonics. This review summarizes recent advancements over the past decade in generating and manipulating single photons, emphasizing the pivotal role of nanostructure coupling. Single-photon emission systems—such as nonlinear crystals, solid-state defects, quantum dots, carbon nanotubes, and two-dimensional materials—are categorized quantitatively based on their ability to achieve high purity, indistinguishability, and brightness, presented in a three-dimensional technology map. Furthermore, nanostructure engineering is showcased for manipulating properties such as emission direction, polarization, chirality, and entanglement of single photons. By elucidating these critical aspects, this review aims to advance understanding of how advancements in nanostructured environments promise to shape the future of single-photon generation and manipulation within quantum nanophotonics.
We review recent advances towards the realization of quantum networks based on atom-like solid-state quantum emitters coupled to nanophotonic devices. Specifically, we focus on experiments involving the negatively charged silicon-vacancy color center in diamond. These emitters combine homogeneous, coherent optical transitions and a long-lived electronic spin quantum memory. We discuss optical and spin properties of this system at cryogenic temperatures and describe experiments where silicon-vacancy centers are coupled to nanophotonic devices. Finally, we discuss experiments demonstrating quantum nonlinearities at the single-photon level and two-emitter entanglement in a single nanophotonic device.
Light-matter interaction is the foundation for numerous important quantum optical phenomena, which may be harnessed to build practical devices with higher efficiency and unprecedented functionality. Nanoscale engineering is seen as a fruitful avenue to significantly strengthen light-matter interaction and also make quantum optical systems ultra-compact, scalable, and energy efficient. This research focuses on color centers in diamond that share quantum properties with single atoms. These systems promise a path for the realization of practical quantum devices such as nanoscale sensors, single-photon sources, and quantum memories. In particular, we explored an intriguing methodology of utilizing nanophotonic structures, such as hyperbolic metamaterials, nanoantennae, and plasmonic waveguides, to improve the color centers performance. We observed enhancement in the color center’s spontaneous emission rate, emission directionality, and cooperativity over a broad optical frequency range. Additionally, we studied the effect of plasmonic environments on the spin-readout sensitivity of color centers. The use of CMOS-compatible epitaxially grown plasmonic materials in the design of these nanophotonic structures promises a new level of performance for a variety of integrated room-temperature quantum devices based on diamond color centers.
Photons are very promising resources for the whole field of quantum information processing. Bulk optics are currently not suitable for the realization of complex quantum optical schemes due to several drawbacks. The ongoing miniaturization of photonic structures due to the availability of sophisticated nanofabrication has provided huge opportunities for physical research of novel phenomena in nanophotonic systems and quantum technological applications. These include quantum information processing such as quantum computing, quantum communication, quantum metrology, and quantum sensing. Quantum communication is already quite advanced with several quantum key distribution (QKD) systems commercially available offering absolute security. Photonic quantum technologies are enabling breakthroughs in experimental tests of quantum physics and are close to practical applications of quantum technologies in imaging, secure communications, ultrasensitive metrology and quantum computing. There are several advantages to encoding a quantum bit onto a photon: the preparation and manipulation of single photons is easy, and the photonic qubit is a natural candidate for quantum imaging and communications. Furthermore, the qubit can be encoded in various degrees of freedom such as on the position, phase, time-bin, energy, angular momentum, polarization of the photon—or a combination of these. This flexibility leads to enormous opportunities for scientific exploration and in practical applications. This special issue on “Photonic Quantum Technologies” presents selected papers on photonic quantum systems from leading groups in the world. The articles represent a flavor of the cutting-edge research that is going on in this area. The studied material systems range from molecules to semiconductor quantum emitters. A major challenge is the design of telecom photon emitters with high efficiency, good yield, spectral purity, stability and the possibility of mass manufacture. We believe that this Special Issue will provide an overview of recent exciting developments in the field of photonic quantum technologies, serving to keep researchers up-to-date with the latest progress and spurring on new concepts in this field.