Some time ago in a far off land, I kept a website. It was a cozy little website, housing a few bits and bobs that I had made and thought to share should other people find them at all useful. It was hosted with my ISP, accessible via a free domain, which made things cheap and easy for me, but also meant that if I were ever to move I'd have to find a new host, or lose my site.

Of course I moved and I lost my site. This was a couple of years ago, now. From then until now I've been meaning to get this thing back up and running at some point, but lack of time and real impetus meant that it didn't happen. Recently I got my butt into gear and began a focused effort to finally get it off the ground, getting myself some cheap hardware and a new domain name for the purpose.

What you see here is the result—welcome to Quantum Furball! Over the next little while I'll be reposting old things (backdated as accurately as I can guess), along with things I should've posted at the time, and I hope to [...]

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Generating entangled photon states is vital for numerous quantum communications and quantum computation primitives. Here we pioneer a new approach to in-fiber generation of entangled photon pairs. We take inspiration from a technique in bulk-optics, where two nonlinear crystals are sandwiched close together, and splice two pieces of birefringent optical fiber together at 90 degree orientation. With suitable compensation optics, all of which could be implemented in fiber, we show fidelity with a maximally-entangled Bell state of better than 92%.

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Here we detail our work on optoelectronics implementing a high-speed high-fidelity source of optical quantum states for quantum encryption.

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We perform a thorough theoretical analysis of the expected key rate, success of Bell test, and teleportation distance of experiments performed between the ground and a satellite in low Earth orbit. Our findings demonstrate that successful, regularly repeatable demonstrations are feasible with current technologies and relatively small telescopes.

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An ensemble cast detail the new physics that could be explored by taking quantum optics experiments into space. My first publication as part of Prof. Thomas Jennewein's group, I contributed details about near-term tests and our present work at the Institute for Quantum Computing, and helped out with logistics and proofing.

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Following on from our prior paper, here we take a closer theoretical look at the different measurement approaches one can use to discriminate between nonorthogonal quantum states when given multiple copies. We examine the behaviour of these schemes in both limits of moderate number of copies and as the number of copies tends towards infinity (the latter of which took quite a long time to determine for the overall optimal scheme), and we identify the quantum mixture regimes in which certain measurements become the same. Indeed, we show that for more than 2% mixture and a large number of copies, the naive measurement strategy is as good as any other.

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