  Quantum volume is a single-number metric which, loosely speaking, reports the
number of usable qubits on a quantum computer. While improvements to the
underlying hardware are a direct means of increasing quantum volume, the metric
is "full-stack" and has also been increased by improvements to software,
notably compilers. We extend this latter direction by demonstrating that error
mitigation, a type of indirect compilation, increases the effective quantum
volume of several quantum computers. Importantly, this increase occurs while
taking the same number of overall samples. We encourage the adoption of quantum
volume as a benchmark for assessing the performance of error mitigation
techniques.
