arXiv subjects

Ben M. Sparkes

Publications and source records attributed to Ben M. Sparkes.

4 recordsLinked to original sources

arXiv2024

Characterization of near-infrared to telecom frequency conversion in a rubidium-filled hollow-core photonic-crystal fiber

We investigate near-infrared to telecommunications frequency conversion via a diamond four-wave mixing scheme in rubidium vapor contained within a hollow-core photonic-crystal fiber. The strong light-atom interaction in the fiber results in lower pump power requirements and higher conversion efficiency than can be achieved under equivalent conditions in a rubidium vapor cell. We also observe non-intuitive pump and signal frequency dependence of the four-wave mixing efficiency in the fiber due to the large nonlinearities present in the system. These results indicate the potential for hollow-core fibers to provide a scalable solution to quantum information network infrastructure, with additional modelling required for a full understanding of the extreme atom-light interaction effects present.

physics.atom-ph↗

arXiv2018

High-efficiency cold-atom transport into a waveguide trap

We have developed and characterized an atom-guiding technique that loads $3\times10^6$ cold rubidium atoms into hollow-core optical fibre, an order-of-magnitude larger than previously reported results. This result was possible because it was guided by a physically realistic simulation that could provide the specifications for loading efficiencies of 3% and a peak optical depth of 600. The simulation further showed that the demonstrated loading efficiency is limited solely by the geometric overlap of the atom cloud and the optical guide beam, and is thus open to further improvement with experimental modification. The experimental arrangement allows observation of the real-time effects of light-assisted cold atom collisions and background gas collisions by tracking the dynamics of the cold atom cloud as it falls into the fibre. The combination of these observations, and physical understanding from the simulation, allows estimation of the limits to loading cold atoms into hollow-core fibres.

physics.atom-ph↗

arXiv2016

Dual-rail optical gradient echo memory

We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6 degrees phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration.

quant-ph↗

arXiv2012

Spatial mode storage in a gradient echo memory

Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a lambda-GEM system. Using a high-speed triggered CCD, we demonstrate the storage of complex spatial modes and images. We also present an in-principle demonstration of spatial multiplexing by showing selective recall of spatial elements of a stored spin wave. Using our measurements, we consider the effect of diffusion within the atomic vapour and investigate its role in spatial decoherence. Our measurements allow us to quantify the spatial distortion due to both diffusion and inhomogeneous control field scattering and compare these to theoretical models.

quant-ph↗