Crosstalk Robust Quantum Error Correction

Quantum error correction (QEC) holds the promise to enable fault-tolerant and scalable quantum computing. The performance analysis of QEC codes is commonly based on an incoherent and independent noise model since it is easy to simulate. Such a noise model, however, is far from realistic in current quantum hardware. For example, correlated error (crosstalk) is a significant source of error and poses relatively unknown impacts on code performances, especially when it happens between data and ancillary qubits. In this study, we investigate various types of crosstalk noise across multiple hardware platforms and quantify their impacts on the performances of repetition code and surface code. Based on our findings, we introduce crosstalk-robust implementation of QEC via extra stabilizer checks and flag qubit design. In addition, we discuss the issue of logical crosstalk in an $[[n,k>1,d]]$ code block and provide analytical criteria under which physical crosstalk will not be converted to logical crosstalk. Together, our analytical and numerical results shed light on designing QEC codes that are robust against hardware-realistic noise and pave the way for reliable experimental realization.