Tailored nanoscale quantum light sources, matching the specific needs of use cases, are crucial building blocks for photonic quantum technologies. Several different approaches to realize solid-state quantum emitters with high performance have been pursued and different concepts for energy tuning have been established. However, the properties of the emitted photons are always defined by the individual quantum emitter and can therefore not be controlled with full flexibility. Here we introduce an all-optical nonlinear method to tailor and control the single photon emission. We demonstrate a laser-controlled down-conversion process from an excited state of a semiconductor quantum three-level system. Based on this concept, we realize energy tuning and polarization control of the single photon emission with a control-laser field. Our results mark an important step towards tailored single photon emission from a photonic quantum system based on quantum optical principles.
Tailored nanoscale quantum light sources, matching the specific needs of use cases, are crucial building blocks for photonic quantum technologies. Several different approaches to realize solid-state quantum emitters with high performance have been pursued and different concepts for energy tuning have been established. However, the properties of the emitted photons are always defined by the individual quantum emitter and can therefore not be controlled with full flexibility. Here we introduce an all-optical nonlinear method to tailor and control the single photon emission. We demonstrate a laser-controlled down-conversion process from an excited state of a semiconductor quantum three-level system. Based on this concept, we realize energy tuning and polarization control of the single photon emission with a control-laser field. Our results mark an important step towards tailored single photon emission from a photonic quantum system based on quantum optical principles.
Much recent effort has focused on coupling individual quantum emitters to optical microcavities in order to produce single photons on demand, enable single-photon optical switching, and implement functional nodes of a quantum network. Techniques to control the bandwidth and frequency of the outgoing single photons are of practical importance, allowing direct emission into telecommunications wavelengths and "hybrid" quantum networks incorporating different emitters. Here, we describe an integrated approach involving a quantum emitter coupled to a nonlinear optical resonator, in which the emission wavelength and pulse shape are controlled using the intra-cavity nonlinearity. Our scheme is general in nature, and demonstrates how the photonic environment of a quantum emitter can be tailored to determine the emission properties. As specific examples, we discuss a high Q-factor, TE-TM double-mode photonic crystal cavity design that allows for direct generation of single photons at telecom wavelengths (1425 nm) starting from an InAs/GaAs quantum dot with a 950 nm transition wavelength, and a scheme for direct optical coupling between such a quantum dot and a diamond nitrogen-vacancy center at 637 nm.
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.
Abstract Hybrid quantum technologies aim to combine diverse quantum systems, mirroring classical computers' integration of electronic, photonic, magnetic, and mechanical components. Quantum dots in semiconductor nanowires emit high-purity, deterministic single photons with high repetition, while atomic ensembles offer photon storage and strong optical nonlinearities controllable by single photons. To interface quantum dots with atomic ensembles successfully, precise optical frequency matching of these two platforms is crucial. We demonstrate a simple, precise, reversible, broad-range, and local method for controlling the emission frequency of individual quantum dots embedded in tapered semiconductor nanowires. We then interface the quantum dots with an atomic ensemble via single-photons matched to hyperfine transitions and slow-light regions of the cesium D1-line. Our approach allows linking atomic and solid-state quantum systems and can potentially also be applied to other types of nanowire-embedded solid-state emitters, as well as for creating devices based on multiple solid-state emitters tuned to produce indistinguishable photons.
Semiconductor quantum-dot cavity systems are promising sources for solid-state-based on-demand generation of single photons for quantum communication. Commonly, the spectral characteristics of the emitted single photon are fixed by system properties such as electronic transition energies and spectral properties of the cavity. In the present work we study cavity-enhanced single-photon generation from the quantum-dot biexciton through a partly stimulated nondegenerate two-photon emission. We show that frequency and linewidth of the single photon can be fully controlled by the stimulating laser pulse, ultimately allowing for efficient all-optical spectral shaping of the single photon.
We report nonlinear resonance fluorescence of an individual semiconductor quantum dot. By driving a single semiconductor quantum dot via a two-photon transition, we probe the linewidth of two-photon excitation processes and show that, similar to their single-photon counterparts, they are close to being Fourier limited at low temperatures. The evolution of the population of excitonic states with increasing Rabi energy exhibits a clear S-shaped behavior, indicative of the nonlinear response via the two-photon excitation process. Numerical calculations of the nonlinear response using a four-level atomic system representing the manifold of excitonic and biexcitonic states in the quantum dot are in excellent agreement with our experiments and reveal the effect of interactions with LA phonons in the solid-state environment. Finally, we demonstrate the formation of dressed states emerging from a nonlinear two-photon interaction between the quantum dot and the optical excitation field. The nonlinear optical dressing induces a mixing of all four excitonic states that allows direct optical tuning of the polarization selection rules and energies of the dressed states in the artificial atom. We expect our results to play a pivotal role for the generation of nonclassical photon pairs desired for applications in quantum communication and fundamental experiments on quantum optical properties of photons.
Photonic quantum technologies require the integration of high-quality quantum light sources with programmable photonic circuitry to enable on-chip quantum information processing. Semiconductor quantum dots have emerged as a leading platform for quantum light generation, yet their monolithic integration with cryogenic-compatible, programmable photonic circuitry remains challenging. Here we demonstrate a programmable quantum photonic platform that enables simultaneous control of highly coherent quantum dot-based single photon emitters and reconfigurable optical elements at cryogenic temperatures. System-level integration enables individual electrical and optical addressing of active components on a single chip, allowing their concurrent operation while preserving coherent non-classical light emission. We demonstrate multiple quantum-photonic functionalities, including pure single-photon generation, two-photon interference, and resonant transmission and reflection measurements of integrated emitters. These results mark a step from isolated quantum-optical devices towards programmable quantum-photonic hardware platforms capable of combining coherent quantum emitters with large-scale photonic functionality.