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Title: Deterministic quantum feedback control in probabilistic atom-photon entanglement
Author: Barter, Oliver
ISNI:       0000 0004 6494 7164
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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The prospect of a universal quantum computer is alluring, yet formidable. Smaller scale quantum information processing, however, has been demonstrated. Quantum networks, interlinking flying and stationary qubits, and linear optical quantum computing (LOQC) are both good candidates for scaling up such computations. A strongly coupled atom-cavity system is a promising approach for applications in these fields, both as a node in a quantum network, and as a source of photons for LOQC. This thesis demonstrates the versatile capabilities of an atom-cavity system comprising a single 87Rb atom within a macroscopic high-finesse Fabry-Pérot cavity. It operates intermittently for periods of up to 100 μs, with single-photon repetition rates of 1 MHz and an intra-cavity production efficiency of up to 85%. Exploiting the long coherence time of around 500 ns, the photons are subdivided into d time bins, with arbitrary amplitudes and phases, thus encoding arbitrary qudits. High fidelity quantum logic is shown, operating a controlled-NOT gate integrated into a photonic chip with a classical fidelity of 95.9+1.4-1.7 %. Additionally, the generation of entanglement is verified and non-classical correlations between events separated by periods exceeding the travel time across the chip by three orders of magnitude are observed. Photonic quantum simulation is performed, using temporally encoded qudits to mimic the correlation statistics of both fermions and anyons, in addition to bosons. Finally measurement-based quantum feedback is demonstrated and used to actively control the routing of temporal qubits.
Supervisor: Kuhn, Axel Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Atomic & Laser Physics ; Cavity QED ; Quantum Computing ; Quantum Feedback