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Author: Patrick Michael Harrington Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 142
Book Description
The interaction between a superconducting circuit and its environment can cause decoherence. However, interactions with an environment are necessary for quantum state preparation and measurement. Through the dynamics of open quantum systems, the environment is a resource to control and readout superconducting circuit states. I present an experimental result demonstrating qubit state stabilization from engineered dissipation with a microwave photonic crystal. In addition, I discuss the statistical arrow of time in the dynamics of continuous quantum measurement. These results demonstrate an interplay between open quantum system dynamics and statistics, which highlights the role of both dissipation and measurement for quantum control.
Author: Patrick Michael Harrington Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 142
Book Description
The interaction between a superconducting circuit and its environment can cause decoherence. However, interactions with an environment are necessary for quantum state preparation and measurement. Through the dynamics of open quantum systems, the environment is a resource to control and readout superconducting circuit states. I present an experimental result demonstrating qubit state stabilization from engineered dissipation with a microwave photonic crystal. In addition, I discuss the statistical arrow of time in the dynamics of continuous quantum measurement. These results demonstrate an interplay between open quantum system dynamics and statistics, which highlights the role of both dissipation and measurement for quantum control.
Author: Chunqing Deng Publisher: ISBN: Category : Dielectric loss Languages : en Pages : 159
Book Description
This thesis discusses a series of experimental and theoretical studies on fast control and decoherence in superconducting quantum circuits. These two subjects are complementary aspects of the problem of improving the gate fidelities in quantum information processing devices based on superconducting circuits. In the first part of this thesis, we present experiments on fast control of a superconducting flux qubit using strong driving. We explore driving with short pulses and a driving strength significantly exceeding the transition frequency. The observed dynamics is described in terms of quasienergies and quasienergy states, in agreement with Floquet theory. We observe the role of pulse shaping in the dynamics, as determined by non-adiabatic transitions between Floquet states. In addition, based on adiabatic perturbation theory in the Floquet picture, we propose a control scheme for fast and high-fidelity single-qubit operations with strong driving. These results pave the way to quantum control with a fidelity beyond the threshold of fault-tolerant quantum computation. In the second part of this thesis, we discuss experimental methods and present the characterization of decoherence in superconducting resonators and superconducting qubits. Firstly, we present an analysis method on the measurements of photon loss in superconducting resonators. We use this method to characterize the microwave loss of aluminum oxide, an important material in superconducting circuits. The power and temperature dependence of the measured loss is consistent with loss due to two-level defects in amorphous materials. Secondly, we present experimental results on decoherence and noise spectroscopy of a superconducting flux qubit. Using the qubit as a noise spectrometer, we perform detailed measurements on the power spectral density of the flux noise in superconducting circuits over a wide range of frequencies, from 10^-3 to 10^8 Hz, and over a temperature range from 35 to 130 mK. We also present measurements of frequency and temperature dependence of the qubit energy relaxation.
Author: Georg M. Reuther Publisher: Logos Verlag Berlin GmbH ISBN: 3832528466 Category : Computers Languages : en Pages : 158
Book Description
Superconducting quantum circuits are promising candidates for solid-state based quantum computation. However, minimizing dissipation caused by external noise sources remains a tough challenge. Here, we present an analytic dissipative theory for a complex circuit of two resonators coupled via a flux qubit. In this 'quantum switch', the qubit acts as a tunable coupler between the resonators, which enables switching their interaction on and off. A natural application of this setup is to create entangled two-resonator states. However, it turns out that, even if the qubit has no dynamics, qubit dissipation affects the resonators to a considerable degree. For successful quantum information processing, it is desirable to demonstrate the coherence of qubit time evolution in single-shot experiments without too much backaction on the qubit. In the second part of this thesis, we present a novel scheme for a time-resolved single-run measurement of coherent qubit dynamics. For a charge qubit probed by a weak high-frequency signal, we find that the reflected outgoing signal possesses a time-dependent phase shift that is proportional to a qubit observable. A similar approach is presented for a flux qubit coupled to a resonantly driven high-frequency oscillator, which serves as a meter device for monitoring the time-resolved qubit dynamics.
Author: Michel Devoret Publisher: OUP Oxford ISBN: 0191503177 Category : Science Languages : en Pages : 601
Book Description
This book gathers the lecture notes of courses given at the 2011 summer school in theoretical physics in Les Houches, France, Session XCVI. What is a quantum machine? Can we say that lasers and transistors are quantum machines? After all, physicists advertise these devices as the two main spin-offs of the understanding of quantum mechanical phenomena. However, while quantum mechanics must be used to predict the wavelength of a laser and the operation voltage of a transistor, it does not intervene at the level of the signals processed by these systems. Signals involve macroscopic collective variables like voltages and currents in a circuit or the amplitude of the oscillating electric field in an electromagnetic cavity resonator. In a true quantum machine, the signal collective variables, which both inform the outside on the state of the machine and receive controlling instructions, must themselves be treated as quantum operators, just as the position of the electron in a hydrogen atom. Quantum superconducting circuits, quantum dots, and quantum nanomechanical resonators satisfy the definition of quantum machines. These mesoscopic systems exhibit a few collective dynamical variables, whose fluctuations are well in the quantum regime and whose measurement is essentially limited in precision by the Heisenberg uncertainty principle. Other engineered quantum systems based on natural, rather than artificial degrees of freedom can also qualify as quantum machines: trapped ions, single Rydberg atoms in superconducting cavities, and lattices of ultracold atoms. This book provides the basic knowledge needed to understand and investigate the physics of these novel systems.
Author: Robert Hadfield Publisher: Springer ISBN: 3319240919 Category : Computers Languages : en Pages : 256
Book Description
This book presents the basics and applications of superconducting devices in quantum optics. Over the past decade, superconducting devices have risen to prominence in the arena of quantum optics and quantum information processing. Superconducting detectors provide unparalleled performance for the detection of infrared photons in quantum cryptography, enable fundamental advances in quantum optics, and provide a direct route to on-chip optical quantum information processing. Superconducting circuits based on Josephson junctions provide a blueprint for scalable quantum information processing as well as opening up a new regime for quantum optics at microwave wavelengths. The new field of quantum acoustics allows the state of a superconducting qubit to be transmitted as a phonon excitation. This volume, edited by two leading researchers, provides a timely compilation of contributions from top groups worldwide across this dynamic field, anticipating future advances in this domain.
Author: Schneider, Andre Publisher: KIT Scientific Publishing ISBN: 3731510324 Category : Science Languages : en Pages : 170
Book Description
Quantum sensing is a vast and emerging field enabling in-situ studies of quantum systems and hence the development of quantum hybrid systems. This work creates the fundament of direct superconducting-magnetic hybrid systems by developing a local microwave sensing scheme and studying the influence of a static magnetic field on a superconducting qubit. Finally, a proof-of-principle hybrid system is demonstrated, which opens the path towards superconducting-magnetic quantum circuits.
Author: Mark Dykman Publisher: OUP Oxford ISBN: 0191637548 Category : Science Languages : en Pages : 432
Book Description
The book provides a unifying insight into fluctuation phenomena in a broad variety of vibrational systems of current interest. It consists of individual chapters written by leading experts in the field. The chapters are self-contained and complement each other. The ongoing rapid development of well-characterized mesoscopic vibrational systems has made it possible to address fundamental physics problems and to explore new approaches to quantum and classical measurements, with applications to quantum information, condensed matter physics, and engineering. The book gives an account of major results in this direction. The topics include dynamics and quantum control of microcavity modes coupled to qubits, measurements with bifurcation-based amplifiers and new types of such amplifiers; switching rate scaling and new quantum mechanisms of metastable decay; wave mixing and parametric excitation in the quantum regime; collective phenomena and the interaction-induced discrete time symmetry breaking; and back-action and shot noise in electron-vibrational systems.
Author: Mollie Elisheva Schwartz Publisher: ISBN: Category : Languages : en Pages : 144
Book Description
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.
Author: Kurt Jacobs Publisher: Cambridge University Press ISBN: 1139992198 Category : Science Languages : en Pages : 729
Book Description
Recent experimental advances in the control of quantum superconducting circuits, nano-mechanical resonators and photonic crystals has meant that quantum measurement theory is now an indispensable part of the modelling and design of experimental technologies. This book, aimed at graduate students and researchers in physics, gives a thorough introduction to the basic theory of quantum measurement and many of its important modern applications. Measurement and control is explicitly treated in superconducting circuits and optical and opto-mechanical systems, and methods for deriving the Hamiltonians of superconducting circuits are introduced in detail. Further applications covered include feedback control, metrology, open systems and thermal environments, Maxwell's demon, and the quantum-to-classical transition.
Author: Patrick Michael Harrington
Author: Patrick Michael Harrington
Author: Luca Chirolli
Author: Chunqing Deng
Author: Georg M. Reuther
Author: Michel Devoret
Author: Robert Hadfield
Author: Schneider, Andre
Author: Mark Dykman
Author: Mollie Elisheva Schwartz
Author: Kurt Jacobs