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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Here we take our knowledge of adaptive quantum control and apply it to enhance phase measurement when we are given a limited set of entangled quantum states. We show the measurement of a completely unknown phase at precision that is in principle below the limit of standard techniques.

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It's known to be impossible to, with 100% accuracy, discriminate between two different quantum states that are not orthogonal. In this paper we look at how accurately you can make this determination when you are given multiple identical copies of one of the two nonorthogonal states. We consider different measurements you can perform, and find that a measurement strategy that performs optimally when the states in question are pure actually performs poorer than a naive “majority vote” scheme when the states have some mixture. We experimentally demonstrate these schemes and derive (and also demonstrate) an adaptive measurement scheme that performs optimally in all conditions, and compare it to the fundamental limit.

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This paper presents a thorough theoretical treatment (with some bonus new experimental results) of our recent demonstrations of phase measurement algorithms which variously beat the standard limit and achieve the fundamental limit of precision. We show how to do this without resorting to entangled states, both with and without adaptive measurements.

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We were (or more specifically, our theory collaborator Prof. Howard Wiseman was) invited to write a paper for IEEE Journal of Selected Topics in Quantum Electronics. Here we describe several of the experiments recently taking place in our (or more specifically, Prof. Geoff Pryde's) laboratory, of which Howard is an integral part. It discusses the recent work on phase measurement, with some bonus theoretical details, as well as touching briefly on some soon-to-be-published work on adaptive quantum state discrimination.

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