Applications in nanophotonics and optical quantum information processing often require just one photon at a time. Although typical single-photon emitters rely on electronic states localized at the nanometer scale, the authors find that carbon nanotubes over 2 $\ensuremath{\mu}$m long exhibit photon antibunching at room temperature. Monte Carlo simulations and first-passage theory reveal that high-purity single-photon emission from this system is possible in principle, by means of efficient exciton-exciton annihilation. These results point to design strategies for single-photon sources, and provide important insight into excitonic processes in carbon nanotubes.
Applications in nanophotonics and optical quantum information processing often require just one photon at a time. Although typical single-photon emitters rely on electronic states localized at the nanometer scale, the authors find that carbon nanotubes over 2 \ensuremathμm long exhibit photon antibunching at room temperature. Monte Carlo simulations and first-passage theory reveal that high-purity single-photon emission from this system is possible in principle, by means of efficient exciton-exciton annihilation. These results point to design strategies for single-photon sources, and provide important insight into excitonic processes in carbon nanotubes.
We report the first observation of photon antibunching in the photoluminescence from single carbon nanotubes. The emergence of a fast luminescence decay component under strong optical excitation indicates that Auger processes are partially responsible for inhibiting two-photon generation. Additionally, the presence of exciton localization at low temperatures ensures that nanotubes emit photons predominantly one by one. The fact that multiphoton emission probability can be smaller than 5% suggests that carbon nanotubes could be used as a source of single photons for applications in quantum cryptography.
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.
Carbon nanotubes (CNTs) have been studied exhaustively in terms of electronic and mechanical properties. A large repertoire of potential applications has been demonstrated for these one-dimensional systems of rolled-up sheets of carbon. To date, most of the optical studies on CNTs have focused more on characterization. Högele et al. now show that CNTs exhibit quantum optical behavior. Photons, being bosons, like to bunch together. However, in quantum systems such as atoms and artificial atoms, the confinement of carriers can split the pack behavior, resulting in the photons being emitted one at a time. For applications such as ultrasecure communication, such antibunching behavior is desirable. These authors excite a single CNT with a laser pulse and observe that light is emitted as single photons upon relaxation. The results suggest that CNTs may extend their repertoire beyond logic circuits and other electronic devices, finding application in quantum optoelectronics. — ISO
It is well-known that strong Coulomb effects in carbon nanotubes lead to formation of the so-called bright and (forbidden one-photon optical transition) exciton states, and dramatically decrease the efficiency of one-photon light emission via trapping of the carriers by states. We suggest and demonstrate that the proper use of these bright and exciton states with distinctively different recombination times may turn the situation around: the use of quantum coherence and multiphoton schemes of excitation potentially not only allow one to efficiently manipulate the dark states, but can also create conditions for efficient light generation in different frequency regions, produce slow or fast light, implement quantum light storage, and media with a negative refractive index. We discuss possible applications of the quantum coherent effects to quantum-optical carbon nanotube devices that have a potential for suitable performance at elevated temperatures, because the binding energies of excitons in single-walled nanotubes are hundreds-of-meV high.
It is strong Coulomb effects in carbon nanotubes that lead to formation of the so-called "bright" and "dark" (forbidden one-photon optical transition) exciton states, and dramatically decrease the efficiency of one-photon light emission via trapping of the carriers by "dark" states. We demonstrate that the proper use of these "bright" and "dark" exciton states with distinctively different recombination times may turn the situation around: the use of quantum coherence and multiphoton schemes of excitation potentially not only allow one to efficiently manipulate the dark states, but can also create conditions for efficient light generation in different frequency regions, produce "slow" or "fast" light, implement quantum light storage, media with a negative refractive index, and other quantum-optical regimes. Possible quantum-optical carbon nanotube devices have a potential for suitable performance at elevated temperatures, because the binding energies of excitons in single-walled nanotubes are hundreds-of-meV high.
The development of a robust light source that emits one photon at a time is an outstanding challenge in quantum science and technology. Here, at the transition from many to single photon optical communication systems, fully quantum mechanical effects may be utilized to achieve new capabilities, most notably perfectly secure communication via quantum cryptography. Practical implementations place stringent requirements on the device properties, including stable photon generation, room temperature operation, and efficient extraction of many photons. Single photon light emitting devices based on fluorescent dye molecules, quantum dots, and carbon nanotube material systems have all been explored, but none have simultaneously demonstrated all criteria. Here, we describe the design, fabrication, and characterization of a bright source of single photons consisting of an individual Nitrogen-vacancy color center (NV center) in a diamond nanowire operating in ambient conditions. The nanowire plays a positive role in increasing the number of single photons collected from the NV center by an order of magnitude over devices based on bulk diamond crystals, and allows operation at an order of magnitude lower power levels. This result enables a new class of nanostructured diamond devices for room temperature photonic and quantum information processing applications, and will also impact fields as diverse as biological and chemical sensing, opto-mechanics, and scanning-probe microscopy.