This PDF file contains the front matter associated with SPIE Proceedings Volume 12206, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

Quantum dots coupled to high-Q cavities can induce optical transparency that provides photon switching capabilities. However, the optical access to such cavities can be inefficient due to their restrictive optical modes. Here, we observe optical transparency of ∼ 80% induced by a quantum dot coupled to a cavity with an efficient optical access, the low-Q bullseye cavity, due to the destructive interference of reflected light. Together with optical lifetimes of quantum dots as short as 80 ps, and the coherent manipulation capabilities of their spin, the transparency induced by coupling these dots to bullseye cavities makes them promising for quantum technologies.

During recent years, quantum dots have become an increasingly established source of highly entangled photons ¹. The main motivation for the development of this technology has resided in the expectation that a resonantly driven quantum emitter can offer a path towards on-demand photon pair generation ². In fact, state-of-the-art sources relying on spontaneous parametric down-conversion intrinsically suffer from multipair emission at high pair generation rates, which causes a tradeoff between brightness and degree of entanglement ³. Despite the key importance of this aspect, the experimental study of how multiphoton emission affects the entanglement properties of quantum dot-based sources has received surprisingly little attention. In this paper we report the investigation of the multipair emission of the source under quasi-deterministic resonant two-photon excitation without filtering the excitation laser using polarization suppression. The focus is on measuring the real multipair emission entering in entanglement-based measurements, minimizing measurement artefacts from the setup and in particular from the excitation source. This is investigated by measuring the second-order correlation function at zero-time delay in several measurement conditions, including spectral filtering. Our work confirms that the multipair emission is provided also for entanglement-based measurement conditions and thus helps the design of efficient photon sources for quantum information and communication technologies.

As trapped ion systems add more ions to allow for increasingly sophisticated quantum processing and sensing capabilities, the traditional optical-mechanical laboratory infrastructure that make such systems possible are in some cases the limiting factor in further growth of the systems. One promising solution is to integrate as many, if not all, optical components such as waveguides and gratings, single-photon detectors, and high extinction ratio optical switches/modulators either into ion traps themselves or into auxiliary devices that can be easily integrated with ion traps. Here we report on recent efforts at Sandia National Laboratories to include integrated photonics in our surface ion trap platforms.

I will discuss our recent proposal on deterministic generation of photonic repeater graph states using only a single quantum emitter, our plans for its experimental implementation, and its applications in quantum repeaters and networks.

We have demonstrated a packaged Silicon photon pair source. The spiral silicon waveguide source is 500 nm x 220 nm x 2 cm long and was packaged with input/output optical fibers enabling turn-key generation of photon pairs by connecting the input optical fiber to a telecommunication grade laser. In this work, we experimentally characterized the generation of bi-photons by spontaneous four-wave mixing in the Silicon waveguide. The insertion loss of the chip, after packaging, was measured to be approximately 15 dB (3 dB/facet, waveguide propagation loss of less than 1.5 dB/cm, 6 dB from splitters sequence). We investigated the phase matching of the source by wavelength tuning the 1 nm bandpass filters and found that the generated bi-photons have a half-bandwidth of 10 nm about the pump wavelength. We investigate pulse pumping using an actively mode-locked fiber laser with a 500 MHz repetition rate, pulse duration of approximately 30 ps and peak pulse power of 400 mW. Excitation of the pulsed source with a power of 1.4 mW through the chip generated 300 kHz coincidence rates after passing the chip’s output through a series of spectral bandpass filters (-1.4 db in channel 1 and -2.4 dB in channel 2 of filter loss and approximately 85 % efficiency of the detectors: inferred on-chip pair generation rate of 58 MHz). We also investigate two sources with 6 mW of continuous-wave pump power to generate 1550 nm bi-photons, generating 6.0 kHz coincidence rates (inferred on-chip pair generation rate of 2.3 MHz).

Monolayer transition metal dichalcogenides (TMDs) are promising 2D semiconductors that feature direct bandgaps useful for various quantum and optoelectronic applications. We present on our progress in establishing a cryogenic photoluminescence setup using a cryogenic probe station with bare multi-mode fibers that allows for active-device biasing of novel material platforms. Using this system, we are able to detect the photoluminescence signal from various chemical vapor deposited (CVD) and molecular beam epitaxy (MBE) grown 2D semiconductors on sapphire (0001) substrates in vacuum. We observe a temperature dependent direct bandgap red-shift of around 40nm (from 8K to 450K) for CVD grown monolayer WS₂ and CVD grown monolayer WSe₂ on sapphire (0001) substrates. We observe a temperature dependent direct bandgap red-shift of around 37nm (from 6K to 450K) for MBE grown monolayer MoSe₂ on sapphire (0001) substrates. Interestingly, for monolayer MoS₂ on sapphire (0001) substrates, we observe the emergence of a strong photoluminescence signal at cryogenic temperatures below 100K, in addition to the A exciton luminescence signal, which is attributed to bound excitons.

The metal-semiconductor interface structure, which can convert photon energy into electrons by internal photon-emission effect, is utilized as one kind of photodetectors. In the Schottky device, the barrier limits the detectable wavelength and the detection response, so how to amplify the detection signal is an important issue. Here, we first quantify the effect of applied bias on the energy barrier reduction mechanism from a mathematical equation. Furthermore, we fabricate metal/semiconductor Schottky devices and experimentally demonstrate the optimization of optical response by image-force lowering effect. As a result, experiment showed a 21 times enhancement in responsivity after an image-force lowering effect was induced.