Mitigating global depolarizing noise with noise estimation circuits*

A significant problem for existing quantum computers is noise. While there are many distinct noise channels, the depolarizing noise model can often appropriately describe average noise for large circuits involving many qubits and gates. We present a method to mitigate the global depolarizing noise by first estimating its rate by executing a noise estimation circuit and then correcting the output of the target circuit using the estimated noise rate. A noise estimation circuit is a circuit that has a similar structure as the target circuit, has a well-defined output, and is classically simulable. We further utilize randomized compiling to convert incoherent noise to coherent noise. The method is experimentally validated on several test cases.