Covesion (United Kingdom)

The results of a marine trial for a cold atom system for inertial navigation (HARLEQUIN) is presented. The system is a deployable atom interferometer demonstrator for navigation using inertial measurements. The interferometer is a grating based, Mach-Zehnder interferometer using rubidium-87 to make measurements of acceleration in a single axis. The output of the quantum sensor is used to condition classical sensors, in a quantum-classical hybrid measurement scheme. The subsystems of HARLEQUIN have been tested aboard a marine platform operated by the UK General Lighthouse Authority, to determine its performance in marine environments and informing an upgrade path to a fully deployable quantum sensor. Presented are results from the trial and upgrade path towards a fully deployable quantum sensor.

Tailored laser sources at visible range wavelengths are in ever increasing demand as technologies for quantum computing, sensing, and remote imaging continue to evolve. As these technologies start to move out of the labora-tory and into the field, the requirement for compact, efficient, rugged laser sources makes wavelength conversion of established laser systems and diodes an obvious choice.

<p>We demonstrate two-photon interference and polarization entanglement at 2090 nm, constituting a crucial leap towards free-space mid-infrared quantum communication systems in a spectral region with high atmospheric transparency and reduced solar background.</p>

We present a device-independent certification of near-maximal polarization entanglement at 2.1μm. The 2-2.5-μm waveband offers reduced solar background, low- loss propagation in the atmosphere, and low-loss, low-dispersion transmission in hollow-core fibers and silicon waveguides.

“Cold atoms” can be used as ultra-sensitive sensors for measuring accelerations and are capable of mapping changes in the strength of gravity across the surface of the Earth. They could offer significant benefits to existing space based gravity sensing capabilities. Gravity sensors in space are already used for many Earth observation applications including monitoring polar ice mass, ocean currents and sea level. Cold atom sensors could enable higher resolution measurements which would allow monitoring of smaller water sources and discovery of new underground natural resources which are currently undetectable. The adoption of cold atom technology is constrained by low technology readiness level (TRL). Teledyne e2v and its partners are addressing this maturity gap through project Cold Atom Space PAyload (CASPA) which is an Innovate UK and Engineering and Physical Sciences Research Council (EPSRC) funded project, involving the University of Birmingham as science lead, XCAM, Clyde Space, Covesion, Gooch & Housego, and the University of Southampton. Through the CASPA project the consortium have built and vibration tested a 6U (approximate dimensions: 100 × 200 × 300 mm) cube Satellite (CubeSat) that is capable of laser cooling atoms down to 100’s of micro kelvin, as a pre-cursor to gravity sensors for future Earth observation missions.

Periodically poled lithium niobate (PPLN) waveguides are a proven and popular means for efficient wavelength conversion. However, conventional PPLN waveguides typically have small mode field diameters (MFD) (≲6 µm) or significant insertion and/or propagation losses, limiting their ability to operate at multi-watt power levels. In this work we utilise zinc indiffused PPLN ridge waveguides that have a larger MFD, favourable pump/SHG modal overlap, and low insertion losses. Here for the first time, we have demonstrated continuous wave (CW) spectral narrowing from a PPLN waveguide, both with high efficiency and multi-watt second harmonic generation (SHG). 2.5 W of 780 nm has been produced by SHG of an amplified 1560 nm telecom laser with a device efficiency of 58% in a 4.0-cm long ridge waveguide. We have modelled conversion efficiency and applied experimentally measured waveguide parameters to show excellent agreement to the SHG spectra. Spectral narrowing of the full width half maximum (FWHM) of 35.7% has been measured as the nonlinear drive is increased. This work demonstrates that single-pass, multi-watt, CW SHG at 780 nm is feasible from our PPLN waveguide in the large conversion regime.

We demonstrate two-photon interference and polarization entanglement at 2090 nm, constituting a crucial leap towards free-space mid-infrared quantum communication systems in a spectral region with high atmospheric transparency and reduced solar background.

Quantum-optical technologies are transforming communication and metrology by enabling security and sensitivity beyond classical limits. Currently, these technologies are available at visible, near-infrared (NIR) and telecom wavelengths but are strongly underdeveloped at longer wavelengths. There is a growing demand for quantum sources operating in the 2 μm region for various applications. For example, such sources can enable daylight satellite-to-ground based quantum communications by taking advantage of an atmospheric transparency window with reduced solar blackbody radiation compared to telecom wavelengths [1,2,3]. Moreover, squeezed 2 μm sources are expected to have an impact on quantum metrology. For example, in gravitational wave detectors (eg. LIGO), such long wavelengths could reduce the quantum noise and scattering loss from crystalline silicon test masses [4]. Here, we report the generation and characterisation of a photon pair source at 2.080 μm with coincidence-to-accidental ratio (CAR) exceeding 10.

We demonstrate a high-pulse-energy, synchronously-pumped (7.19MHz), 100ps, widely tunable MgO:PPLN OPO providing 0.49µJ pulses at 1.5µm and 0.19µJ pulses at 3.6µm. A single-mode fiber is employed in the OPO to keep the 42m-long cavity compact.