Room-temperature generation of heralded single photons on silicon chip with switchable orbital angular momentum

In quantum optics, orbital angular momentum (OAM) is very promising to achieve high-dimensional quantum states due to the nature of infinite and discrete eigenvalues, which is quantized by the topological charge of l. Here, a heralded single-photon source with switchable OAM modes is proposed and demonstrated on silicon chip. At room-temperature, the heralded single photons with 11 OAM modes (l=2~6, -6~-1) have been successfully generated and switched through thermo-optical effect. We believe that such an integrated quantum source with multiple OAM modes and operating at room-temperature would provide a practical platform for high-dimensional quantum information processing. Moreover, our proposed architecture can also be extended to other material systems to further improve the performance of OAM quantum source.

Evaluation of an elliptically polarized undulator for the future Taiwan Photon Source

The resonant photon energy of an adjustable-phase undulator (APU) is varied with the relative motion of the magnet arrays along the longitudinal direction. There exists, however, a transverse field gradient (TFG) of order 100 T/m in an APU of small gap (∼10 mm). Whereas the TFG might affect the electron beam as it contributes to the dynamic field integral and the radiation integrals, the TFG might also degrade the performance of the synchrotron radiation due to the transverse position-dependent magnetic field. The effects of the TFG on the present Taiwan Photon Source (TPS) and future TPS-upgraded are analyzed to investigate the feasibility of an APU that operates in the soft x-ray region.

Device cooling features in wiggler synchrotron workstations

Construction of the 4+ generation Siberian circular photon source (SKIF synchrotron) has started in Novosibirsk. It will initially be equipped with six research workstations. For two stations, synchrotron radiation is generated by superconducting wigglers, whose radiation power approaches 49 kW, and the power density on the axis is 92 kW/mrad2. Most of the optical devices of the stations operate in a vacuum. The high energy density of the synchrotron beamline and the requirements for the values of thermal deformations lead to difficult conditions for the thermal management of optical elements. The article provides an overview of the applied and promising cooling systems; an example of a 3D calculation of a thermal diamond filter of workstation 1-5 is given, the limit for the thermal load of the filter, at which the temperature of the diamond plate will not exceed 600 °C, is estimated.

Wave–particle duality quantified for the first time

Scientists in South Korea have used a precisely controlled photon source to measure a photon’s degree of “waveness” and “particle-ness”.

Using a pre-kicker to ensure safe extractions from the HEPS storage ring

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring light source under construction. The swap-out injection is adopted with the depleted bunch recycled via high-energy accumulation in the booster. The extremely high beam energy density of the bunches with an ultra-low emittance (about 30 pm horizontally and 3 pm vertically) and high bunch charges (from 1.33 to 14.4 nC) extracted from the storage ring could cause hazardous damage to the extraction Lambertson magnet in case of extraction kicker failure. To this end, we proposed the use of a pre-kicker to spoil the bunches prior to extraction, significantly reducing the maximum beam energy density down to within a safe region while still maintaining highly efficient extractions. The main parameters of the pre-kicker are simulated and discussed.

Some Features of the Direct and Inverse Double-Compton Effect as Applied to Astrophysics

In the present paper, the process of inverse double-Compton (IDC) scattering is considered in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using the QED S-matrix formalism for the derivation of a cross-section of direct double-Compton (DDC) scattering and assuming detailed balance conditions, an analytical expression for the cross-section of the IDC process is presented. It is shown that at fixed energies of incident photons, the inverse cross-section has no infrared divergences, and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result, the physical frequency profile of the scattered radiation for DDC as well as for IDC processes is a function of both the intensity and line shape of the incident photon field.

Optical fibre-based single photon source using InAsP quantum dot nanowires and gradient-index lens collection

We present a compact, fibre-coupled single photon source using gradient-index (GRIN) lenses and an InAsP semiconductor quantum dot embedded within an InP photonic nanowire waveguide. A GRIN lens assembly is used to collect photons close to the tip of the nanowire, coupling the light immediately into a single mode optical fibre. The system provides a stable, high brightness source of fibre-coupled single photons. Using pulsed excitation, we demonstrate on-demand operation with a single photon purity of 98.5% when exciting at saturation in a device with a source-fibre collection efficiency of 35% and an overall single photon collection efficiency of 10%. We also demonstrate “plug and play” operation using room temperature photoluminescence from the InP nanowire for room temperature alignment.