Nonclassical Effects In Strongly Coupled Dissipative Quantum Systems

Author : Mollie Elisheva Schwartz
Publisher :
ISBN 13 :
Total Pages : 144 pages
Book Rating : 4.:/5 (994 download)

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Download or read book Engineering Dissipation to Generate Entanglement Between Remote Superconducting Quantum Bits written by Mollie Elisheva Schwartz and published by . This book was released on 2016 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting quantum circuits provide a promising avenue for scalable quantum computation and simulation. Their chief advantage is that, unlike physical atoms or electrons, these ``artificial atoms'' can be designed with nearly-arbitrarily large coupling to one another and to their electromagnetic environment. This strong coupling allows for fast quantum bit (qubit) operations, and for efficient readout. However, strong coupling comes at a price: a qubit that is strongly coupled to its environment is also strongly susceptible to losses and dissipation, as coherent information leaks from the quantum system under study into inaccessible ``bath'' modes. Extensive work in the field is dedicated to engineering away these losses to the extent possible, and to using error correction to undo the effects of losses that are unavoidable. This dissertation explores an alternate approach to dissipation: we study avenues by which dissipation itself can be used to generate, rather than destroy, quantum resources. We do so specifically in the context of quantum entanglement, one of the most important and most counter-intuitive aspects of quantum mechanics. Entanglement generation and stabilization is critical to most non-trivial implementations of quantum computing and quantum simulation, as it is the property that distinguishes a multi-qubit quantum system from a string of classical bits. The ability to harness dissipation to generate, purify, and stabilize entanglement is therefore highly desirable. We begin with an overview of quantum dissipation and measurement, followed by an introduction to entanglement and to the superconducting quantum information architecture. We then discuss three sets of experiments that highlight and explore the powerful uses of dissipation in quantum systems. First, we use an entangling measurement to probabilistically generate entanglement between two qubits separated by more than one meter of ordinary cable. This represents the first achievement of remote entanglement in a superconducting qubit system, which will be a critical capability as quantum computers and simulators scale. We then use a nearly-quantum limited amplifier to unravel individual quantum trajectories of the system under that entangling measurement, performing the first systematic exploration of entangled trajectories in any physical implementation. We finally demonstrate deterministic entanglement by engineering a lossy quantum environment to efficiently generate and stabilize entangled states with both frequency and symmetry selectivity. These experiments provide evidence that explicitly building dissipation into an engineered quantum system can enable, rather than hinder, the study of fundamental quantum mechanics and complex many-body Hamiltonians.