Superconducting quantum computing (SQC) has achieved remarkable progress in recent years, garnering significant scientific and technological interests. This review provides a concise overview of the historical development of SQC, detailing fabrication methodologies for superconducting quantum chips and implementations of quantum gate operations. It compiles experimental progress in SQC over the past few years, including the preparation of multi-qubit entangled states, random circuit sampling experiments, demonstrations of quantum error correction based on surface codes, error mitigation techniques and quantum simulations. This review also discusses experimental progress related to boson-encoded qubits, fluxoniums and qudits. Finally, the current challenges in scaling are analyzed, and potential solutions for addressing these limitations are explored.
Superconducting quantum computing (SQC) has achieved remarkable progress in recent years, garnering significant scientific and technological interests. This review provides a concise overview of the historical development of SQC, detailing fabrication methodologies for superconducting quantum chips and implementations of quantum gate operations. It compiles experimental progress in SQC over the past few years, including the preparation of multi-qubit entangled states, random circuit sampling experiments, demonstrations of quantum error correction based on surface codes, error mitigation techniques and quantum simulations. This review also discusses experimental progress related to boson-encoded qubits, fluxoniums and qudits. Finally, the current challenges in scaling are analyzed, and potential solutions for addressing these limitations are explored.
Superconducting qubits are leading candidates in the race to build a quantum computer capable of realizing computations beyond the reach of modern supercomputers. The superconducting qubit modality has been used to demonstrate prototype algorithms in the noisy intermediate-scale quantum (NISQ) technology era, in which non-error-corrected qubits are used to implement quantum simulations and quantum algorithms. With the recent demonstrations of multiple high-fidelity, two-qubit gates as well as operations on logical qubits in extensible superconducting qubit systems, this modality also holds promise for the longer-term goal of building larger-scale error-corrected quantum computers. In this brief review, we discuss several of the recent experimental advances in qubit hardware, gate implementations, readout capabilities, early NISQ algorithm implementations, and quantum error correction using superconducting qubits. Although continued work on many aspects of this technology is certainly necessary, the pace of both conceptual and technical progress in recent years has been impressive, and here we hope to convey the excitement stemming from this progress.
Superconducting quantum circuits (SQCs), composed of superconducting capacitors, inductances, Josephson junctions, and transmission lines, exhibit macroscopic quantum effects at ultra-low temperatures. Due to the extremely low dissipation of superconductors, an important application of SQCs is superconducting qubits with long coherence time. Quantum computing based on superconducting qubits is a leading physical realization method of quantum computing, which is theoretically capable of accelerating many computational problems including quantum simulation, database searching, and optimization. In the long run, to use the power of quantum computing to its full extent, universal quantum computers should be constructed with quantum error correction. In the short term, one of the most pressing targets of the superconducting quantum computing community is to demonstrate quantum advantage using noisy intermediate-scale quantum chips. Both goals rely on the increasing of the number of coupled qubits in a quantum circuit and the quality of these qubits, which dictate the breadth and the depth of a problem it can solve, respectively. The fabrication of SQCs has adopted a few manufacturing processes from conventional integrated circuits. Quantum chips containing multiple superconducting qubits can be made and packaged on a large scale. “Quantum supremacy” has been demonstrated on a quantum chip with fifty-three qubits fabricated using the flip-chip bonding technology. However, to demonstrate quantum advantage, the quality and quantity of qubits need to increase simultaneously. Dissipative channels emerge in circuit design, material preparation, chip fabrication, and working environment, limiting the lifetime of superconducting qubits. For quantum chips with tens to hundreds of qubits, the integration will also introduce extra processing steps which may degrade the qubits, and unwanted coupling to loss channels. Most of these channels are microscopically related to materials constructing the quantum chips, chip surfaces, and material interfaces. Thus, it is important to investigate the material growth and device fabrication of SQCs, and to understand the material related loss mechanisms. This review paper investigates the material related topics in superconducting quantum circuits pertinent to the quantum computing application from a comprehensive perspective. The history of SQCs is briefly mentioned, followed by the peculiar characteristics as an engineerable quantum system, and a roadmap to quantum advantage and universal quantum computing in the next a few years. Technically, the superconducting quantum computer is compared to a Schrodinger’s cat, and can be boiled down into three parts, i.e., quantum chips, the environment, and the operating system, corresponding to the cat, the box, and the observer, respectively. The material related decoherence channels of the SQCs can be sorted into four categories; each will be discussed in details. To fabricate SQCs with minimal loss, the processing technologies are elaborated, including qubit design, material selection, surface treatments, film growth, and Josephson junction, etc. Though there are general guidelines that amorphous materials should be avoided and processing induced damage should be minimized, more is to be investigated due to the emerging of new materials and new fabrication methods. The last part presents the potential application of the superconducting quantum computer and its current state of play. SQC for quantum computing is a multi-discipline research topic, demanding joint efforts from different scientific and technical areas. Materials science and device processing will play important roles along the way to quantum practicality.
Superconducting circuits based on Josephson junctions are regarded as one of the most promising technologies for the implementation of scalable quantum computers. This review presents the basic principles of superconducting qubits and shows the progress of quantum computing and quantum simulation based on superconducting qubits in recent years. The experimental realization of gate operations, readout, error correction codes, as well as some quantum algorithms are summarized, followed by an introduction of quantum simulation. And then some important applications in fields including condensed matter physics, quantum annealing, and quantum chemistry are discussed.
During the last ten years, superconducting circuits have passed from being interesting physical devices to becoming contenders for near-future useful and scalable quantum information processing (QIP). Advanced quantum simulation experiments have been shown with up to nine qubits, while a demonstration of quantum supremacy with fifty qubits is anticipated in just a few years. Quantum supremacy means that the quantum system can no longer be simulated by the most powerful classical supercomputers. Integrated classical-quantum computing systems are already emerging that can be used for software development and experimentation, even via web interfaces. Therefore, the time is ripe for describing some of the recent development of superconducting devices, systems and applications. As such, the discussion of superconducting qubits and circuits is limited to devices that are proven useful for current or near future applications. Consequently, the centre of interest is the practical applications of QIP, such as computation and simulation in Physics and Chemistry.
Quantum computation exploits superposition, entanglement, interference, and measurement to process information.Research has moved from theoretical algorithms to functional devices where the performance is not only limited by qubit physics, but also by the control, compilation, error mitigation, and error correction.This review considers quantum computing on various levels of abstraction, including physical qubits, quantum algorithms, system architecture, fault-tolerance, and emerging applications.Study-specific evidence regarding scale, operational quality, connectivity, control and suppression of errors is compared across the different types of superconducting circuits, trapped ions, semiconductor spin qubits, neutral atoms and photonic processors.The review of the fundamental algorithms, noisy intermediate-scale quantum computing, variational and hybrid quantum-classical approaches, quantum simulation, quantum machine learning, and security implications is also discussed.Measurable progress has been demonstrated in published experiments for logical-qubit operation, below-threshold surface-code memory, programmable photonic sampling and platformspecific scaling.However, the reported metrics are not directly interchangeable, and practical advantage remains task-and baseline-dependent.Further progress will need to be accompanied by coordinated developments in hardware reliability, error correction, classical control, estimates of algorithmic resources, and clear classical method comparisons.