Single-photon sources are essential building blocks in quantum photonic networks, where quantum-mechanical properties of photons are utilised to achieve quantum technologies such as quantum cryptography and quantum computing. Most conventional solid-state single-photon sources are based on single emitters such as self-assembled quantum dots, which are created at random locations and require spectral filtering. These issues hinder the integration of a singlephoton source into a scaleable photonic quantum network for applications such as on-chip photonic quantum processors. In this work, using only regular lithography techniques on a conventional GaAs quantum well, we realise an electrically triggered single-photon source with a GHz repetition rate and without the need for spectral filtering. In this device, a single electron is carried in the potential minimum of a surface acoustic wave (SAW) and is transported to a region of holes to form an exciton. The exciton then decays and creates a single photon in a lifetime of ∼ 100 ps. This SAW-driven electroluminescence (EL) yields photon antibunching with g (2) (0) = 0.39 ± 0.05, which satisfies the common criterion for a single-photon source g (2) (0) < 0.5. Furthermore, we estimate that if a photon detector receives a SAW-driven EL signal within one SAW period, this signal has a 79%-90% chance of being a single photon. This work shows that a single-photon source can be made by combining single-electron transport and a lateral n-i-p junction. This approach makes it possible to create multiple synchronised single-photon sources at chosen positions with photon energy determined by quantum-well thickness. Compared with conventional quantum-dot-based single-photon sources, this device may be more suitable for an on-chip integrated photonic quantum network.The development of single-photon sources is important for many quantum information technologies [1][2][3], such as quantum cryptography [4][5][6], quantum communication [7][8][9], quantum metrology [10, 11], and quantum computation [12, 13]. Currently, most high-performance single-photon sources are self-assembled InGaAs-based quantum dots (QDs) [14][15][16]. However, there are several issues that may limit their integration into practical quantum photonic networks [17][18][19][20][21][22][23][24]. Firstly, in conventional growth of self-assembled QDs, the location and size of each QD are quite random. Therefore, one has to rely on statistics to create structures like optical cavities and gates around a quantum dot. This will be an issue for applications that require several deterministicallyfabricated single-photon sources on a compact chip. Secondly, it is hard to precisely control the size of a quantum dot, which will affect the single-photon energy. Hence, it is challenging to make identical QD single-photon sources, which is essential for applications like quantum computation and a quantum repeater [12,25]. Finally, in order to ensure that a neutral exciton is created in every optical or electrical excitation, the e...

In a model of a gate-patterned quantum device it is important to choose the correct electrostatic boundary conditions (BCs) in order to match experiment. In this study, we model gated-patterned devices in doped and undoped GaAs heterostructures for a variety of BCs. The best match is obtained for an unconstrained surface between the gates, with a dielectric region above it and a frozen layer of surface charge, together with a very deep back boundary. Experimentally, we find a ∼ 0.2 V offset in pinch-off characteristics of one-dimensional channels in a doped heterostructure before and after etching off a ZnO overlayer, as predicted by the model. Also, we observe a clear quantised current driven by a surface acoustic wave through a lateral induced n-in junction in an undoped heterostructure. In the model, the ability to pump electrons in this type of device is highly sensitive to the back BC. Using the improved boundary conditions, it is straightforward to model quantum devices quite accurately using standard software.

We report a postfabrication process for the realization of nanosized light emitting diodes. The method is based on the exposure of the device to an Ar+ laser through an aperture near field optical microscope and can produce a large (&gt;100 fold) increase in the electroluminescence within a near field hot spot as small as 440 nm. A study of morphological, photoluminescence and electroluminescence properties highlights the interplay between oxidation, annealing, and ablation processes for various laser exposure conditions.

Surface acoustic waves (SAWs) have been used to transport single electrons across long distances of several hundreds of microns. They can potentially be instrumental in the implementation of scalable quantum processors and quantum repeaters, by facilitating interaction between distant qubits. While most of the work thus far has focused on SAW devices in doped GaAs/AlGaAs heterostructures, we have developed a method of creating lateral p-n junctions in an undoped heterostructure containing a quantum well, with the expected advantages of having reduced charge noise and increased spin-coherence lifetimes due to the lack of dopant scattering centres. We present experimental observations of SAW-driven single-electron quantised current in an undoped GaAs/AlGaAs heterostructure, where single electrons were transported between regions of induced electrons. We also demonstrate pumping of electrons by a SAW across the sub-micron depleted channel between regions of electrons and holes, and observe light emission at such a lateral p-n junction. Improving the lateral confinement in the junction should make it possible to produce a quantised electron-to-hole current and hence SAW-driven emission of single photons.