  Quantum Volume is a full-stack benchmark for near-term quantum computers. It
quantifies the largest size of a square circuit which can be executed on the
target device with reasonable fidelity. Error mitigation is a set of techniques
intended to remove the effects of noise present in the computation of noisy
quantum computers when computing an expectation value of interest. Effective
quantum volume is a proposed metric that applies error mitigation to the
quantum volume protocol in order to evaluate the effectiveness not only of the
target device but also of the error mitigation algorithm. Digital Zero-Noise
Extrapolation (ZNE) is an error mitigation technique that estimates the
noiseless expectation value using circuit folding to amplify errors by known
scale factors and extrapolating to the zero-noise limit. Here we demonstrate
that ZNE, with global and local unitary folding with fractional scale factors,
in conjunction with dynamical decoupling, can increase the effective quantum
volume over the vendor-measured quantum volume. Specifically, we measure the
effective quantum volume of four IBM Quantum superconducting processor units,
obtaining values that are larger than the vendor-measured quantum volume on
each device. This is the first such increase reported.
