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Author: Edward Matthew Leonard Publisher: ISBN: Category : Languages : en Pages : 118
Book Description
Fault-tolerant quantum computation requires high-fidelity control of qubit states. In superconducting qubits based on Josephson circuits, this is typically achieved via the application of microwave packets generated by mixing the output of a coherent source with an intermediate frequency tone generated and shaped using arbitrary waveform generators. This control style has seen tremendous success, enabling the high-fidelity control of systems comprising many-tens of qubits. However, as systems now scale towards thousands of qubits, the overhead microwave hardware and number of necessary connections to the quantum processor becomes staggering. This will eventually impart a larger-than-practical heat-load on a state-of-the-art large-scale DR. A perhaps natural co-processor technology to superconducting qubits is the family of superconducting electronics based on the Rapid Single Flux Quantum (RSFQ) style of logic circuits, which has been the subject of intense research for the past 30 years and has matured to the point of enabling the construction of complex superconducting arithmetic logic units in a variety of flavors of RSFQ technologies. In this thesis, we present progress towards the integration of superconducting qubits with a simple circuit from the RSFQ family of digital superconducting electronics. A dc/SFQ pulse generator circuit is cofabricated on the same chip as a transmon qubit. Inspired by some early practitioners of nuclear magnetic resonance and their DANTE pulse sequence, we use single flux quantum pulse trains -- flux pulses which are quantized to the superconducting flux quantum and pulse-to-pulse timings which are set by the qubit precession period -- to drive coherent rotations of the transmon state. We measure the error of our quantum gates in this control scheme using randomized benchmarking and find gate fidelities around 95\%. We then characterize the loss in our quantum system in the form of quasiparticle poisoning as a result of operation of the dc/SFQ converter. We conclude with a brief discussion of straightforward improvements to mitigate the deleterious effects of quasiparticles on the quantum circuit and discuss the scalability of this technology in the context of Josephson quantum computing.
Author: Edward Matthew Leonard Publisher: ISBN: Category : Languages : en Pages : 118
Book Description
Fault-tolerant quantum computation requires high-fidelity control of qubit states. In superconducting qubits based on Josephson circuits, this is typically achieved via the application of microwave packets generated by mixing the output of a coherent source with an intermediate frequency tone generated and shaped using arbitrary waveform generators. This control style has seen tremendous success, enabling the high-fidelity control of systems comprising many-tens of qubits. However, as systems now scale towards thousands of qubits, the overhead microwave hardware and number of necessary connections to the quantum processor becomes staggering. This will eventually impart a larger-than-practical heat-load on a state-of-the-art large-scale DR. A perhaps natural co-processor technology to superconducting qubits is the family of superconducting electronics based on the Rapid Single Flux Quantum (RSFQ) style of logic circuits, which has been the subject of intense research for the past 30 years and has matured to the point of enabling the construction of complex superconducting arithmetic logic units in a variety of flavors of RSFQ technologies. In this thesis, we present progress towards the integration of superconducting qubits with a simple circuit from the RSFQ family of digital superconducting electronics. A dc/SFQ pulse generator circuit is cofabricated on the same chip as a transmon qubit. Inspired by some early practitioners of nuclear magnetic resonance and their DANTE pulse sequence, we use single flux quantum pulse trains -- flux pulses which are quantized to the superconducting flux quantum and pulse-to-pulse timings which are set by the qubit precession period -- to drive coherent rotations of the transmon state. We measure the error of our quantum gates in this control scheme using randomized benchmarking and find gate fidelities around 95\%. We then characterize the loss in our quantum system in the form of quasiparticle poisoning as a result of operation of the dc/SFQ converter. We conclude with a brief discussion of straightforward improvements to mitigate the deleterious effects of quasiparticles on the quantum circuit and discuss the scalability of this technology in the context of Josephson quantum computing.
Author: Chuanhong Liu (Ph.D.) Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Superconducting quantum bits (qubits) are a leading platform in the race to realize quantum computing, benefiting from the long coherence and high-fidelity operation and measurement. However, to realize fault-tolerant quantum computing, one still needs to push the superconducting qubit to have longer coherent times and find a practical road map for system scaling up. This thesis discusses two main topics: nonequilibrium quasiparticles, one dominant decoherence channel, and single flux quantum (SFQ)-based digital control, a potentially scalable quantum-classical interface. The huge discrepancy between the measured density of quasiparticle excitations in superconductors and the density predicted by the Bardeen-Cooper-Schrieffer theory is a longstanding mystery in condensed matter physics. This mystery has taken new importance in recent years as researchers work to implement quantum processors based on superconducting quantum circuits, for which nonequilibrium quasiparticles represent a significant coherence channel. It has been proposed that the qubit structure itself acts as a resonant antenna for millimeter-wave radiation so that the broadband blackbody emission from higher temperature stages of the cryostat will efficiently generate quasiparticles at the Josephson junction of the qubit device. In this thesis, we describe the experimental validation of this model. We develop an innovative experimental protocol to y dose our qubit devices with millimeter-wave radiation, and we employ a quantum interferometric gate sequence to map out the detailed spectral response of the qubits. Furthermore, we show that the qubit initialization errors, a significant contributor to the quantum processor infidelity, are dominated by the resonant absorption of pair-breaking radiation. Another open question we explore in this thesis is how to control large-scale qubit arrays that aspire to fault tolerance. The SFQ logic family can be leveraged for superconducting qubits to achieve digital qubit control with a compact, proximal classical co-processor. Here, we implement a quantum-classical multi-chip module involving an SFQ pulse driver flip-chip coupled to a qubit chip. We demonstrate an order-of-magnitude reduction in gate infidelity compared to prior SFQ control implementation. The SFQ control scheme can yield significant reductions in the footprint of large-scale quantum processors, removing a major obstacle to practical quantum error correction.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: National Academies Press ISBN: 030947969X Category : Computers Languages : en Pages : 273
Book Description
Quantum mechanics, the subfield of physics that describes the behavior of very small (quantum) particles, provides the basis for a new paradigm of computing. First proposed in the 1980s as a way to improve computational modeling of quantum systems, the field of quantum computing has recently garnered significant attention due to progress in building small-scale devices. However, significant technical advances will be required before a large-scale, practical quantum computer can be achieved. Quantum Computing: Progress and Prospects provides an introduction to the field, including the unique characteristics and constraints of the technology, and assesses the feasibility and implications of creating a functional quantum computer capable of addressing real-world problems. This report considers hardware and software requirements, quantum algorithms, drivers of advances in quantum computing and quantum devices, benchmarks associated with relevant use cases, the time and resources required, and how to assess the probability of success.
Author: Francesco Tafuri Publisher: Springer Nature ISBN: 3030207269 Category : Technology & Engineering Languages : en Pages : 859
Book Description
This book provides a comprehensive and up-to-date description of the Josephson effect, a topic of never-ending interest in both fundamental and applied physics. In this volume, world-renowned experts present the unique aspects of the physics of the Josephson effect, resulting from the use of new materials, of hybrid architectures and from the possibility of realizing nanoscale junctions. These new experimental capabilities lead to systems where novel coherent phenomena and transport processes emerge. All this is of great relevance and impact, especially when combined with the didactic approach of the book. The reader will benefit from a general and modern view of coherent phenomena in weakly-coupled superconductors on a macroscopic scale. Topics that have been only recently discussed in specialized papers and in short reviews are described here for the first time and organized in a general framework. An important section of the book is also devoted to applications, with focus on long-term, future applications. In addition to a significant number of illustrations, the book includes numerous tables for comparative studies on technical aspects.
Author: Daniel D. Stancil Publisher: John Wiley & Sons Incorporated ISBN: 9781119750758 Category : Computers Languages : en Pages : 0
Book Description
"Digital systems that are most familiar are based on binary digits, or "bits." Each bit can take on either the value "1" or "0", and any arbitrary data can be represented by such a binary representation. In addition, any arbitrary logical operation can be implemented using bits. The text refers to these familiar systems as "classical" systems, since they are governed by the everyday laws of classical physics. Quantum computing is different from classical computing in a number of significant ways, as discussed in 'Principles of superconducting quantum computers'"--
Author: Alexey Feofanov Publisher: KIT Scientific Publishing ISBN: 3866446446 Category : Science Languages : en Pages : 126
Book Description
The results of the research re-ported in this work show that tunable gap flux qubits have a potential for building quantum registers. Cavities coupled to flux qubits can be used for in-formation storage and transfer between qubits. SFS π-shifters provide a simple approach to bias multi-qubit circuits. A possibility to change the qubit resonance frequency while preserving qubit coherence enables implementation of switchable coupling between qubits and cavities.
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: Marquis Matthew McMillan Publisher: ISBN: Category : Languages : en Pages :
Book Description
First mentioned by Richard Feynman in 1981, quantum computers that aim to achieve efficient quantum simulations to solve quantum problems are now being developed in laboratories worldwide, thus making Feynmans scientific dream a life-changing reality. However, we might ask: "why not perform quantum simulations on our classical computers?" While classical computers are limited to binary-bits, quantum computers rely on entanglement and superpositions of quantum-bits (qubits) to execute calculations. This increases the computational power of a quantum computer because of its ability to analyze complex entangled systems in a superposition of states. The state of a qubit is represented as the superposition of the basis states of a two level quantum system. Quantum states are prepared by performing operations on qubits that are referred to as 'quantum-gates' and are the key component to all quantum computing operations. Our goal in this thesis was to use the IBM-Q platform to carry out experiments characterizing the transmon, a type of superconducting qubit that is derived from the Josephson-junction. A Josephson-junction consists of two superconductors separated by an insulator; this leads to a non-linear energy spectrum in the transmon that causes it to deviate from an evenly spaced energy spectrum (such as the quantum harmonic oscillator). We begin by modeling the transmon Hamiltonian by plotting the eigenvalues for an array of circuit parameters. Modeling the transmon Hamiltonian provides a deeper understanding into the quantization of a transmon. In comparison to the quantum harmonic oscillator, the transmon has a non-linear energy difference between each state. This enables the first two energy levels of our transmon to be the computational zero and one states. Consequently, the transmon has low charge sensitivity making it reliable under most circuit parameters. For experimentally accessible circuit parameters, the energy difference between the lowest two levels exist in the microwave regime. Therefore, qubit states are prepared by applying microwave pulses accessed through the IBMQ OpenPulse platform. We mapped the fundamental frequency of the qubit by driving microwave pulses with an array of frequencies and measuring the qubit response. Characterization through OpenPulse is a stepping-stone for cloud-based systems and tests the limits of contactless-quantum computation. Finally, we theoretically study the physics of light-matter interactions of an ideal two-level system, and compare the experimentally measured transmon response to on-resonant and off-resonant microwave radiation to the expected model. At low drive amplitudes, the experiments demonstrate an agreement with the expected dependencies, but deviate at stronger amplitudes. In this context, we study the impact of pulse rise-fall envelopes on the qubit response.
Author: Rafael Luque Merino Publisher: ISBN: Category : Languages : en Pages :
Book Description
Transmon qubits are at the forefront of solid state platforms for quantum computing. In this thesis, results obtained from the experimental study of a transmon qubit in a 3D cavity are presented. A complete view of the experiment is given, including cryogenic methods, microwave signal processing and spectroscopic and pulsed measurements of the transmon qubit. Lastly, partial results on state discrimination set the next step towards fully coherent control of the qubit.
Author: A. M. Zagoskin Publisher: Cambridge University Press ISBN: 1139495763 Category : Science Languages : en Pages : 345
Book Description
Quantum engineering – the design and fabrication of quantum coherent structures – has emerged as a field in physics with important potential applications. This book provides a self-contained presentation of the theoretical methods and experimental results in quantum engineering. The book covers topics such as the quantum theory of electric circuits, theoretical methods of quantum optics in application to solid state circuits, the quantum theory of noise, decoherence and measurements, Landauer formalism for quantum transport, the physics of weak superconductivity and the physics of two-dimensional electron gas in semiconductor heterostructures. The theory is complemented by up-to-date experimental data to help put it into context. Aimed at graduate students in physics, the book will enable readers to start their own research and apply the theoretical methods and results to their current experimental situation.
Author: Edward Matthew Leonard
Author: Edward Matthew Leonard
Author: Chuanhong Liu (Ph.D.)
Author: National Academies of Sciences, Engineering, and Medicine
Author: Francesco Tafuri
Author: Daniel D. Stancil
Author: Alexey Feofanov
Author: Robert Hadfield
Author: Marquis Matthew McMillan
Author: Rafael Luque Merino
Author: A. M. Zagoskin