A Qubit Field Guide

Claudio Conti

Philip Krantz, Morten Kjærgaard, F. Yan +3 more

The aim of this review is to provide quantum engineers with an introductory guide to the central concepts and challenges in the rapidly accelerating field of superconducting quantum circuits. Over the past twenty years, the field has matured from a predominantly basic research endeavor to a one that increasingly explores the engineering of larger-scale superconducting quantum systems. Here, we review several foundational elements—qubit design, noise properties, qubit control, and readout techniques—developed during this period, bridging fundamental concepts in circuit quantum electrodynamics and contemporary, state-of-the-art applications in gate-model quantum computation.

M. J. Storcz, M. Mariantoni, H. Christ +6 more

We consider a superconducting charge qubit coupled to distinct orthogonal electromagnetic field modes belonging to a coplanar wave guide and a microstrip transmission line resonators. This architecture allows the simultaneous implementation of a Jaynes-Cummings and anti-Jaynes-Cummings dynamics, a resonant method for generating mesoscopic qubit-field superpositions and for field-state reconstruction. Furthermore, we utilize this setup to propose a field measurement technique that is, in principle, robust to qubit dephasing and field relaxation due to a fast pre-measurement.

David K. Ferry

Mikhail Pavlov

Abstract This practical guide provides a detailed introduction to quantum logic gates and unitary operators as implemented on the IBM Q platform. It focuses on the fundamental gate structures used in quantum programming, particularly within the Composer interface, and provides screenshots and detailed descriptions of each operator’s functionality. The guide emphasizes the operational role of gates in controlling qubit states and constructing quantum circuits. To enhance understanding, the behavior of gates is visualized on the Bloch sphere, demonstrating how single-qubit operations rotate qubit states around the XXX, YYY, and ZZZ axes, as well as how phase shifts and amplitude adjustments modify the qubit. These operations are essential for measurement, state preparation, and precise manipulation of quantum systems. The relevance of this study is underscored by the rapid development of quantum technologies and the increasing accessibility of quantum computing platforms like IBM Q. A thorough understanding of quantum gates and their implementations is critical for advancing quantum algorithm design and for training specialists capable of deploying quantum computational solutions in fields ranging from cryptography to complex physical system simulations. This guide provides both theoretical insights and practical exercises, bridging the gap between abstract quantum mechanics and applied quantum programming, thereby equipping readers with foundational skills for effective circuit construction and quantum computation.