F73: Error Mitigation Theory and Extensions

Tue. March 7, 9:12 a.m. – 9:48 a.m. PST

Room 405

Suppressing noise in physical systems is of fundamental importance. As quantum computers mature, quantum error correcting codes (QECs) will be adopted in order to suppress errors to any desired level. However in the noisy, intermediate-scale quantum (NISQ) era, the complexity and scale required to adopt even the smallest QEC is prohibitive: a single logical qubit needs to be encoded into many thousands of physical qubits. Recent breakthroughs [Phys. Rev. X 11, 031057; Phys. Rev. X 11, 041036] have shown that for the crucial case of estimating expectation values of observables (key to almost all NISQ algorithms) one can indeed achieve an effective exponential suppression. The core idea of these techniques is to take multiple independently prepared circuit outputs to create a state whose symmetries prevent errors from contributing bias to the expected value. A number of recent works have built on these ideas and developed various theoretical generalisations as well as specific hardware architectures. For example, in a multicore approach multiple quantum processors perform the same noisy quantum computation whose outputs are used to `verify' each other using imperfect quantum links. In this talk I will review the basic principles of exponential error suppression techniques and also discuss the more recent developments.