  Zero-noise extrapolation is a quantum error mitigation technique that has
typically been studied under the ideal approximation that the noise acting on a
quantum device is not time-correlated. In this work, we investigate the
feasibility and performance of zero-noise extrapolation in the presence of
time-correlated noise. We show that, in contrast to white noise,
time-correlated noise is harder to mitigate via zero-noise extrapolation
because it is difficult to scale the noise level without also modifying its
spectral distribution. This limitation is particularly strong if "local"
gate-level methods are applied for noise scaling. However, we find that
"global" noise scaling methods, e.g., global unitary folding, can be
sufficiently reliable even in the presence of time-correlated noise. We also
introduce gate Trotterization as a new noise scaling technique that may be of
independent interest.
