Microwave Techniques In Superconducting Quantum Computers

The first of its kind, Microwave Techniques in Superconducting Quantum Computers introduces microwave and quantum engineers to essential practical techniques and theoretical foundations crucial for operating and implementing hardware in superconducting quantum processors. This practical resource covers an extensive range of topics, including Introduction to Quantum Physics, Introduction to Quantum Computing, Superconducting Qubits, Microwave Systems, Microwave Components, Principles of Electromagnetic Compatibility, Control Hardware for Superconducting Qubits, and Principles of Cryogenics. Such technical knowledge equips the reader with essential skills to succeed in the demanding industries and research settings surrounding quantum technologies. With clearly outlined learning objectives and coherent explanations of intricate concepts, this is a must-have reference for a wide spectrum of professionals, including microwave and quantum engineers, technical managers, technical sales engineers in quantum computing and microwave companies, as well as newcomers entering this field. To enrich the reader's experience, this book offers additional complementary content accessible via www.quaxys.com/book.

Explore the intersection of computer science, physics, and electrical and computer engineering with this discussion of the engineering of quantum computers In Principles of Superconducting Quantum Computers, a pair of distinguished researchers delivers a comprehensive and insightful discussion of the building of quantum computing hardware and systems. Bridging the gaps between computer science, physics, and electrical and computer engineering, the book focuses on the engineering topics of devices, circuits, control, and error correction. Using data from actual quantum computers, the authors illustrate critical concepts from quantum computing. Questions and problems at the end of each chapter assist students with learning and retention, while the text offers descriptions of fundamentals concepts ranging from the physics of gates to quantum error correction techniques. The authors provide efficient implementations of classical computations, and the book comes complete with a solutions manual and demonstrations of many of the concepts discussed within. It also includes: A thorough introduction to qubits, gates, and circuits, including unitary transformations, single qubit gates, and controlled (two qubit) gates Comprehensive explorations of the physics of single qubit gates, including the requirements for a quantum computer, rotations, two-state systems, and Rabi oscillations Practical discussions of the physics of two qubit gates, including tunable qubits, SWAP gates, controlled-NOT gates, and fixed frequency qubits In-depth examinations of superconducting quantum computer systems, including the need for cryogenic temperatures, transmission lines, S parameters, and more Ideal for senior-level undergraduate and graduate students in electrical and computer engineering programs, Principles of Superconducting Quantum Computers also deserves a place in the libraries of practicing engineers seeking a better understanding of quantum computer systems.

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.

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.

After years of academic development, the circuit quantum electrodynamics is entering the age of applications. This thesis was realized in this context of creating tools to bridge the gap between an astounding academic quantum system, superconducting circuits, and a grand goal, the universal quantum computer. A likely blueprint for quantum processors consists in the assembly of a large number of elementary modules arranged in a network.In this experimental thesis, a possible node for such a network, the quantum node, was developed and fabricated using state-of-the-art techniques for 2D superconducting microwave circuits. This node was first used to implement a novel sequential readout method for a superconducting qubit. This experiment, first proposed in 2013 by Sete et al., potentially allows for faster, more accurate read out of superconducting qubits. The read out of qubits is one of the several bottlenecks limiting the development of fault-tolerant superconducting quantum computers, which made this project both useful as a demonstration of the quantum node and for applications. This novel readout method achieves readout performances close to state-of-the-art of superconducting qubit readout even though the chip was not optimized for that purpose.During this work, we also contributed to two other experiments engineering quantum measurement and dissipation with superconducting circuits. First, a dedicated circuit was developed to demonstrate a new form of quantum measurement: the multiplexed photon number measurement. In that experiment led by A. Essig and Q. Ficheux, a superconducting transmon quantum bit is read out at multiple frequencies simultaneously to extract more than one bit of information about the number of photons contained in a microwave resonator coupled to that quantum bit.Second, we contributed to the experimental demonstration of the exponential suppression of bit-flips in a qubit encoded in a Schrödinger Cat state of a microwave mode. This experiment led by R. Lescanne and Z. Leghtas, demonstrates the improvement by a factor 300 of the lifetime of a qubit thanks to the autonomous error correction realized through the engineering of the dissipation of a microwave mode.

Superconducting quantum circuits are among the most promising solutions for the development of scalable quantum computers. Built with sizes that range from microns to tens of metres using superconducting fabrication techniques and microwave technology, superconducting circuits demonstrate distinctive quantum properties such as superposition and entanglement at cryogenic temperatures. This book provides a comprehensive and self-contained introduction to the world of superconducting quantum circuits, and how they are used in current quantum technology. Beginning with a description of their basic superconducting properties, the author then explores their use in quantum systems, showing how they can emulate individual photons and atoms, and ultimately behave as qubits within highly connected quantum systems. Particular attention is paid to cutting-edge applications of these superconducting circuits in quantum computing and quantum simulation. Written for graduate students and junior researchers, this accessible text includes numerous homework problems and worked examples.

This project has experimentally characterized the coherent quantum nature of the superconducting persistent current qubits which were fabricated in the trilayer niobium technology. The quantum levels of these qubits have been mapped out using both standard microwave frequency spectroscopy as well as a new technique of amplitude spectroscopy. Important to the future implementation of these qubits for quantum computing applications is the demonstration of microwave sideband cooling of the qubits as well as a resonant read-out scheme. In addition to characterizing the quantum nature of a single qubit, this work has also explored the use of Rapid-Single-Flux superconducting circuits to rapidly control the qubit system.

Quantum computing has the potential to achieve better scaling for factoring large numbers, simulating quantum behavior of molecules, and sampling random number distributions. Quantum dot qubits in silicon show strong promise as a qubit platform due to the long decoherence times measured as well as the possibility of leveraging techniques from classical processor fabrication towards scaling to large qubit systems. We examine coupling quantum dot qubits to a superconducting coplanar waveguide, which functions as a single-photon resonator, and this system enables coherent communications between qubit systems. We are concerned with both the hardware and low-level software of quantum computation. We examine geometric modifications to the heterostructure and the electrode geometry to boost the capacitive coupling between a triple dot system and a resonator. We find decreasing the vertical separation between the electrode connected to the resonator and the dots has a positive impact on the coupling strength. Continuing hardware simulations, we consider the issue of low device yield in Si-MOS devices, where despite large singlet-triplet splittings, there was no evidence of Pauli spin blockade. We attributed this to impurities within the oxide and performed a series of simulations that allowed us to determine the required impurity density to lift spin blockade, and found this density consistent with the device yield. Switching to considering different qubit encodings, we compared and contrasted the behavior of three qubits that are resonantly coupled to a superconducting resonator. The three encodings were the charge dipole (CD) qubit, the charge quadrupole (CQ) qubit, and the quantum dot hybrid qubit (QDHQ). In terms of entangling a one photon state with a qubit state, the CD qubit and the CQ qubit behaved similarly, however the CQ qubit does allow arbitrary single qubit gates while being protected from quasistatic charge noise. The QDHQ exhibited better performance (measured by infidelity) when operated at a second-order-sweet spot than both other encodings in the typical charge noise regime. Furthermore, the quantum dot hybrid qubit enables multiple operating points, offering greater tuning flexibility when considering implementation in actual devices.

Recent advancements in quantum-enabled systems present a variety of new opportunities and challenges. These technologies are important developments for a variety of computing, communications, and sensing applications. However, many materials and components relevant to quantum-enabled systems exist outside of the United States, and it is important to promote the development of assured domestic sources of materials, manufacturing capabilities, and expertise. The National Academies of Sciences, Engineering, and Medicine convened a 2-day workshop to explore implications and concerns related to the application of quantum-enabled systems in the United States. This workshop focused on quantum-enabled computing systems, quantum communications and networks, and quantum sensing opportunities. Participants explored the path to quantum computing, communications, and networks, opportunities for collaboration, as well as key gaps, supply chain concerns, and security issues. This publication summarizes the presentations and discussions from the workshop.

Many superconducting technologies such as rapid single flux quantum computing (RSFQ) and superconducting quantum interference devices (SQUIDs) rely on the modulation of nonlinear dynamics in Josephson junctions for functionality. More recently, however, superconducting devices have been developed based on the switching and thermal heating of nanowires for use in fields such as single photon detection and digital logic. In this Master's thesis, I will use resistive shunting to control the nonlinear heating of a superconducting nanowire and compare the resulting dynamics to those observed in Josephson junctions. In particular, I will use a microwave drive to modulate the nonlinear behavior of the shunted nanowire, and will relate the observed results to the AC Josephson effect. New nanowire devices based on these conclusions may have promising applications in fields such as parametric amplification and frequency multiplexing.