2005/08/11 by K. L. Pregnell, Pregnell, K. L. · 1 citation
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Neural Networks and Reservoir Computing #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Physics (quant-ph) #quant-ph
paper · pdf · doi:10.48550/arxiv.quant-ph/0508088
Ph.D thesis. Submitted April 2004
arxiv created 2005/08/11 · openalex publication_date 2005/08/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
This thesis is concerned with retrodiction and measurement in quantum optics. The latter of these two concepts is studied in particular form with a general optical multiport device, consisting of an arbitrary array of beam-splitters and phase-shifters. I show how such an apparatus generalizes the original projection synthesis technique, introduced as an in principle technique to measure the canonical phase distribution. Just as for the original projection synthesis, it is found that such a generalised device can synthesize any general projection onto a state in a finite dimensional Hilbert space. One of the important findings of this thesis is that, unlike the original projection synthesis technique, the general apparatus described here only requires a classical, that is a coherent, reference field at the input of the device. Such an apparatus lends itself much more readily to practical implementation and would find applications in measurement and predictive state engineering. If we relax the above condition to allow for just a single non-classical reference field, we show that the apparatus is capable of producing a single-shot measure of canonical phase. That is, the apparatus can project onto any one of an arbitrarily large subset of phase eigenstates, with a probability proportional to the overlap of the phase state and the input field. Unlike the original projection synthesis proposal, this proposal requires a binomial reference state as opposed to a reciprocal binomial state. We find that such a reference state can be obtained, to an excellent approximation, from a suitably squeezed state. The analysis of these measurement apparatuses is performed in the less usual, but completely rigorous, retrodictive formalism of quantum mechanics.