Multi-qubit time-varying quantum channels for NISQ-era superconducting quantum processors

• DOI: 10.48550/arxiv.2207.06838
• Publication Date: 2022-01-01
• Authors: Josu Etxezarreta ...; Patricio Fuentes; Antonio deMarti i...; Javier Garcia‐Frias; J.R. Fonollosa; Pedro M. Crespo
• Keywords: Dephasing; Flux qubit

Recent experimental studies have shown that the relaxation time ($T_1$) and dephasing ($T_2$) of superconducting qubits fluctuate considerably over time. To appropriately consider this time-varying nature $T_1$ $T_2$ parameters, a new class quantum channels, known as Time-Varying Quantum Channels (TVQCs), has been proposed. In previous works, realizations multi-qubit TVQCs assumed to be equal for all an error correction block, implying random variables describe fluctuations are block-to-block uncorrelated, but qubit-wise perfectly correlated same block. Physically, these decoherence parameters explained by incoherent coupling with unstable near-resonant two-level-systems (TLS), which indicates such variations may local each system. article, we perform correlation analysis times processors ibmq\_quito, ibmq\_belem, ibmq\_lima, ibmq\_santiago ibmq\_bogota. Our results show it is reasonable assume Based on results, discuss when block uncorrelated (as well from block-to-block), scenario named Fast Channel (FTVQC). Furthermore, lower bound capacity general FTVQCs based quantity refer ergodic capacity. Finally, use numerical simulations study performance codes (QECC) they operate FTVQCs.