Superconducting logic is a type of logic circuit or logic gate that makes use of the unique properties of superconductors, such as zero-resistance wires, ultrafast Josephson junction switches, and magnetic flux quantization (fluxoid). Superconducting computing is a type of cryogenic computing because superconductive electronic circuits must be cooled to cryogenic temperatures, typically below 10 kelvin, in order to operate.
To fully develop quantum computers and advance the field, new research tools are required. A theoretical tool for analyzing large superconducting circuits has now been developed and tested by researchers. Superconducting quantum bits, the smallest units of a quantum computer, are used to store information in these circuits. Circuit size is important because noise protection tends to come at the expense of increased circuit complexity. There are currently few tools available for modeling large circuits.
The fascinating world of quantum mechanics holds the key to the next generation of computing and information processing. Quantum computers are expected to be capable of solving large, extremely complex problems that today’s most powerful supercomputers are incapable of solving.
New research tools are needed to fully develop quantum computers and advance the field. Now researchers have developed and tested a theoretical tool for analyzing large superconducting circuits.
To advance the field and fully develop quantum computers, new research tools are required. Now, researchers at Northwestern University have developed and tested a theoretical tool for analyzing large superconducting circuits. Superconducting quantum bits, or qubits, the smallest units of a quantum computer, are used to store information in these circuits.
Circuit size is important because noise protection tends to come at the expense of increased circuit complexity. There are currently few tools for modeling large circuits, making the Northwestern method an important contribution to the research community.
“Our framework is inspired by methods originally developed for the study of electrons in crystals, and it enables us to obtain quantitative predictions for circuits that were previously difficult or impossible to access,” said Daniel Weiss, the paper’s corresponding and first author. He is a fourth-year graduate student in Jens Koch’s research group, which specializes in superconducting qubits.
Because superconductors have no electrical resistance, electrons can pass through them completely unhindered. Even the best standard conductors, such as copper wires in phone lines or conventional computer chips, have some resistance; overcoming it necessitates operational voltages far greater than those required to induce current in a superconductor. When electrons begin to move through an ordinary conductor, they occasionally collide with its atoms, releasing energy as heat.
Koch, an associate professor of physics and astronomy in the Weinberg College of Arts and Sciences, is a member of the Superconducting Quantum Materials and Systems Center (SQMS) and the Quantum Advantage Co-design Center (C2QA). The US Department of Energy established both national centers last year (DOE). SQMS is dedicated to developing and deploying a quantum computer that is beyond the state-of-the-art, based on superconducting technologies. C2QA is developing the foundational tools required to build scalable, distributed, and fault-tolerant quantum computer systems.
“We are thrilled to be able to contribute to the missions pursued by these two DOE centers and to raise Northwestern’s profile in the field of quantum information science,” Koch said. The Northwestern researchers demonstrate the use of their theoretical tool in their study by extracting quantitative information from a protected circuit that was previously unattainable using standard techniques.
Physical Review Research, an open-access journal, published the details. The researchers focused on protected qubits. These qubits are designed to be noise-free and could have much longer coherence times (how long quantum information is retained) than current state-of-the-art qubits.
These superconducting circuits are unavoidably large, and the Northwestern tool is a means of quantifying their behavior. There are some existing tools for analyzing large superconducting circuits, but they only work well under certain conditions. The Northwestern method is complementary and effective when other tools produce suboptimal results.
Computer chips with superconducting circuits — circuits with no electrical resistance — would be 50 to 100 times more energy-efficient than current chips, an appealing feature has given the rising power consumption of the massive data centers that power the Internet’s most popular sites. Superconducting circuits are used in light detectors that can detect the arrival of a single light particle or photon; this is one of the applications where the researchers tested the nanocryotron.
