Modeling leakage in superconducting quantum computers

Current quantum computing architectures are fragile and prone to various imperfections that limit computational capabilities. In order to better understand behavior of quantum hardware, we need to develop a theoretical framework that captures possibile sources of device errors.

Recent development in noise description allow us to characterize within statistical accuracy net effects of numerous unknown contributions. The most commonly used method for this is based on randomized Pauli channels (PC) approach, that can reflect circuit's fidelity.

In this talk, we discuss a potential extension to PC technique, that can in principle take into account leakage to non-computation basis. The method is based on Weyl matrices. We show the effect of projecting leakage subspace into a qubit space, and compare the method with PC. Finally, we briefly explain possibility of expanding this model to larger dimensions.