Superconducting qubits are the most widely deployed qubit technology in the quantum computing industry today. They are fabricated on silicon chips using techniques adapted from the semiconductor industry, with circuits made from superconducting metals (typically aluminum or niobium) cooled to approximately 15 millikelvin — colder than outer space — in dilution refrigerators. At these temperatures, electrical resistance vanishes and current oscillates quantum mechanically, with the qubit states encoded in the direction or energy of this oscillation.
IBM and Google are the leading proponents of superconducting qubits. IBM's roadmap has progressed from the 127-qubit Eagle processor through 1,121-qubit Condor and beyond, aiming for systems with tens of thousands of qubits. Google's Sycamore processor achieved the first claimed quantum supremacy in 2019, and the company continues to push superconducting qubit performance. Rigetti Computing, a startup, also develops superconducting quantum processors with a focus on hybrid quantum-classical computing.
The strengths of superconducting qubits include fast gate speeds (tens of nanoseconds), leverageable semiconductor fabrication processes, and relatively straightforward scaling of qubit counts on a chip. The weaknesses include short coherence times (typically 100-300 microseconds), the need for expensive cryogenic infrastructure, and sensitivity to manufacturing variation. The technology is evolving rapidly, with each generation of processors improving coherence, connectivity, and error rates. For deeper coverage, see DeepTechIntel's quantum computing section.