Scalable evaluation of quantum-circuit error loss using Clifford sampling

A major challenge in developing quantum computing technologies is to accomplish high precision tasks by utilizing multiplex optimization approaches. Loss functions assessing the overall circuit performance provide the foundation for many optimization techniques. We use the quadratic error loss and the final-state fidelity loss to characterize quantum circuits, which can be efficiently evaluated in a scalable way by sampling from Clifford-dominated circuits. We demonstrate it by numerically simulating 10-qubit quantum circuits with various error models and executing 4-qubit circuits with up to 10 layers of 2-qubit gates on a superconducting quantum processor. Our results pave the way towards the optimization-based quantum device and algorithm design in the NISQ regime.
arXiv:2007.10019