Here we detail our work on optoelectronics implementing a high-speed high-fidelity source of optical quantum states for quantum encryption.
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.
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.
This post marks the completion of my honours thesis, as part of my BSc. (Hons) degree. It was a pleasure to work and learn under the supervision of Prof. Geoff Pryde at Griffith University, in close collaboration with Ben Lanyon in the laboratory of Prof. Andrew White at The University of Queensland.
The project served as my introduction to the world of experimental photonic implementations of quantum information. The aim of the project was to attempt to combine two techniques—quantum nondemolition measurement, and unambiguous state discrimination. The project was successful insofar as the experiment reproduced what we expected to obtain theoretically, though considerably more work would have been required in order to achieve complete nondemolishing unambiguous state discrimination. The PDF of the thesis can be found here.
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