Quantum Characterization of Intermediate Scale Systems (DOD)

Zhen‐Peng Xu

Quantum networks, as a playground for various quantum technologies, describe the distribution of quantum sources represented by edges to different parties represented by nodes in the network. Here, the author introduces a systematic approach to characterize arbitrary quantum networks in the noisy intermediate-scale quantum era, which can be noisy, intermediate-scale, random, and sparse.

Prakash Murali, David C. McKay, Margaret Martonosi +1 more

Crosstalk is a major source of noise in Noisy Intermediate-Scale Quantum (NISQ) systems and is a fundamental challenge for hardware design. When multiple instructions are executed in parallel, crosstalk between the instructions can corrupt the quantum state and lead to incorrect program execution. Our goal is to mitigate the application impact of crosstalk noise through software techniques. This requires (i) accurate characterization of hardware crosstalk, and (ii) intelligent instruction scheduling to serialize the affected operations. Since crosstalk characterization is computationally expensive, we develop optimizations which reduce the characterization overhead. On 3 20-qubit IBMQ systems, we demonstrate two orders of magnitude reduction in characterization time (compute time on the QC device) compared to all-pairs crosstalk measurements. Informed by these characterization, we develop a scheduler that judiciously serializes high crosstalk instructions balancing the need to mitigate crosstalk and exponential decoherence errors from serialization. On real-system runs on 3 IBMQ systems, our scheduler improves the error rate of application circuits by up to 5.6x, compared to the IBM instruction scheduler and offers near-optimal crosstalk mitigation in practice.