Solid-state Single-photon Emitters Research Articles

Combined metallic nano-rings and solid-immersion lenses for bright emission from single InAs/GaAs quantum dots

Solid-state single-photon emitters are key components for integrated quantum photonic devices. However, they can suffer from poor extraction efficiencies, caused by the large refractive index contrast between the bulk material they are embedded in and air: this results in a small fraction (that can be as low as ∼0.1%) of the emitted photons reaching free-space collection optics. To overcome this issue, we present a device that combines a metallic nano-ring, positioned on the sample surface and centered around the emitter, and an epoxy-based super-solid immersion lens, deposited above the ring devices. We show that the combined broadband lensing effect of the nano-ring and the super-solid immersion lens significantly increases the extraction of light emitted by single InAs/GaAs quantum dots into free space: we observe cumulative enhancements that allow us to estimate photon fluxes on the first collecting lens approaching 1 × 106 counts per second, from a single quantum dot in bulk. The combined broad-band enhancement in the extraction of light can be implemented with any kind of classical and quantum solid-state emitter and opens the path to the realisation of scalable bright devices. The same approach can also be implemented to improve the absorption of light, for instance, for small-area broadband photo-detectors.

Room temperature solid-state quantum emitters in the telecom range.

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies.

Photoinduced blinking in a solid-state quantum system

Solid state single photon emitters (SPEs) are one of the prime components of many quantum nanophotonics devices. In this work, we report on an unusual, photo-induced blinking phenomenon of SPEs in gallium nitride (GaN). This is shown to be due to the modification in the transition kinetics of the emitter, via the introduction of additional laser-activated states. We investigate and characterize the blinking effect on the brightness of the source and the statistics of the emitted photons. Combining second-order correlation and fluorescence trajectory measurements, we determine the photo-dynamics of the trap states and characterize power dependent decay rates and characteristic off-time blinking. Our work sheds new light into understanding solid-state quantum system dynamics and, specifically, power-induced blinking phenomena in SPEs.

Solid-state single-photon emitters

This Review summarizes recent progress of single-photon emitters based on defects in solids and highlights new research directions. The photophysical properties of single-photon emitters and efforts towards scalable system integration are also discussed.

Laser-written parabolic micro-antennas for efficient photon collection

Efficient collection of photons from solid-state single-photon emitters, like quantum dots, molecules, or defect centers in diamond, is a very demanding task. Here, we introduce parabolic micro-antennas fabricated by two-photon direct laser-writing to enhance the collection efficiency by directing emitted light into a small solid angle. The antennas can be fabricated on-site at the position of a pre-selected single-photon emitter.

Fault-Tolerant Quantum Communication Based on Solid-State Photon Emitters

We describe a novel protocol for a quantum repeater that enables long-distance quantum communication through realistic, lossy photonic channels. Contrary to previous proposals, our protocol incorporates active purification of arbitrary errors at each step of the protocol using only two qubits at each repeater station. Because of these minimal physical requirements, the present protocol can be realized in simple physical systems such as solid-state single photon emitters. As an example, we show how nitrogen-vacancy color centers in diamond can be used to implement the protocol, using the nuclear and electronic spin to form the two qubits.