Improved error mitigation protocol by restricted evolution

To perform any meaningful computation using NISQ processors, error mitigation protocols need to be deployed in the quantum circuits. Here, we propose a constant runtime error mitigation protocol. Further, we propose a hybrid error mitigation protocol by combining our methods with the probabilistic error cancellation to improve the bias and the sampling overhead in estimating the expectation value of an observable. We showed that the sampling overhead and the bias of our protocol depend on a measure called generalized robustness and we also found bounds on this measure under general noise scenario.