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Dissertation/Thesis Abstract

Engineering Photonic Switches for Quantum Information Processing
by Oza, Neal N., Ph.D., Northwestern University, 2014, 263; 3669298
Abstract (Summary)

In this dissertation, we describe, characterize, and demonstrate the operation of a dual-in, dual-out, all-optical, fiber-based quantum switch. This "cross-bar" switch is particularly useful for applications in quantum information processing because of its low-loss, high-speed, low-noise, and quantum-state-retention properties.

Building upon on our lab's prior development of an ultrafast demultiplexer [1-3] , the new cross-bar switch can be used as a tunable multiplexer and demultiplexer. In addition to this more functional geometry, we present results demonstrating faster performance with a switching window of ≈45 ps, corresponding to >20-GHz switching rates. We show a switching fidelity of >98%, i. e., switched polarization-encoded photonic qubits are virtually identical to unswitched photonic qubits. We also demonstrate the ability to select one channel from a two-channel quantum data stream with the state of the measured (recovered) quantum channel having >96% relative fidelity with the state of that channel transmitted alone. We separate the two channels of the quantum data stream by 155 ps, corresponding to a 6.5-GHz datastream.

Finally, we describe, develop, and demonstrate an application that utilizes the switch's higher-speed, lower-loss, and spatio-temporal-encoding features to perform quantum state tomographies on entangled states in higher-dimensional Hilbert spaces. Since many previous demonstrations show bipartite entanglement of two-level systems, we define "higher" as d > 2 where d represents the dimensionality of a photon. We show that we can generate and measure time-bin-entangled, two-photon, qutrit (d = 3) and ququat (d = 4) states with >85% and >64% fidelity to an ideal maximally entangled state, respectively. Such higher-dimensional states have applications in dense coding [4] , loophole-free tests of nonlocality [5] , simplifying quantum logic gates [6] , and increasing tolerance to noise and loss for quantum information processing [7] .

Indexing (document details)
Advisor: Kumar, Prem
Commitee: Kanter, Gregory S., Mohseni, Hooman, Stern, Nathaniel P.
School: Northwestern University
Department: Electrical and Computer Engineering
School Location: United States -- Illinois
Source: DAI-B 76/05(E), Dissertation Abstracts International
Subjects: Electrical engineering, Quantum physics, Optics
Keywords: Entangled-photon polarimetry, Fiber optics, Higher-dimensional hilbert spaces, Photonic switches, Quantum entanglement, Quantum information processing
Publication Number: 3669298
ISBN: 978-1-321-44759-0
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