Speaker: Dr. Thi Ha Kyaw and Dr. Gaurav Saxena, LG Electronics
Abstract:
Talk 1: A critical limitation of quantum imaginary time evolution-like algorithms in noisy quantum hardware (Thi Ha Kyaw)
Abstract: The variational quantum imaginary time evolution algorithm is efficient in finding the ground state of a quantum Hamiltonian. This algorithm involves solving a system of linear equations in a classical computer and the solution is then used to propagate a quantum wavefunction. Here, we show that owing to the noisy nature of current quantum processors, such a quantum algorithm or the family of quantum algorithms that require classical computation of inverting a matrix with high condition number will require single- and two-qubit gates with very low error probability. Failure to meet such conditions will result in erroneous quantum data propagation even for a relatively small quantum circuit ansatz. Specifically, we find the upper bounds on how the quantum algorithmic error scales with the probability of errors in quantum hardware. Our work challenges the mainstream notion of hybrid quantum-classical quantum algorithms being able to perform under noisy environments while we show such algorithms require very low error quantum gates to get reliable results.
Abstract: 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.