William Hughes

Abstract:

The generation of entanglement between distant atoms via single photons is the basis for networked quantum computing, a promising route to large-scale trapped-ion and trapped-atom processors. Locating the emitter within an optical cavity provides an efficient matter-light interface, but mirror-induced birefringence within the cavity introduces time-dependence to the polarisation of the photons produced. We show that such 'polarisation oscillation' effects can lead to severe loss of fidelity in the context of two-photon, polarisation encoded measurement-based remote entanglement schemes. It is always preferable to suppress these errors at source by minimising mirror ellipticity, but we propose two remedies for systems where this cannot be achieved. We conclude that even modest cavity birefringence can be detrimental to remote entanglement performance, to an extent that may limit the suitability of polarisation-encoded schemes for large-scale quantum networks.

Abstract:

Numerical data generated from python module available at DOI:10.5281/zenodo.7020047. Data are presented and analysed in arxiv 2112.05795

Abstract:

We present a design for an atomic oven suitable for loading ion traps, which is operated via optical heating with a continuous-wave multimode diode laser. The absence of the low-resistance electrical connections necessary for Joule heating allows the oven to be extremely well thermally isolated from the rest of the vacuum system. Extrapolating from high-flux measurements of an oven filled with calcium, we calculate that a target region number density of 100 cm−3, suitable for rapid ion loading, will be produced with 175(10) mW of heating laser power, limited by radiative losses. With simple feedforward to the laser power, the turn-on time for the oven is 15 s. Our measurements indicate that an oven volume 1000 times smaller could still hold enough source metal for decades of continuous operation.