Quantum Volume
A single-number benchmark for quantum computer capability that accounts for qubit count, gate fidelity, connectivity, and other factors. Higher is better.
Quantum volume (QV) is a hardware-agnostic benchmark developed by IBM to measure the overall capability of a quantum computer. Unlike qubit count alone, quantum volume incorporates multiple factors: the number of qubits, their gate fidelity, qubit connectivity (which qubits can interact with which), and circuit depth (how many operations can be run before decoherence destroys the result).
A quantum volume of 2^n means the system can successfully execute random quantum circuits of depth n on n qubits. Doubling quantum volume is roughly equivalent to the improvement made by doubling transistors in classical computing.
Quantum volume has become less central to industry discourse as systems have scaled, with various companies now using different benchmarks. But it remains useful for comparing systems across different architectures.