DynaMite: Dynamic Measurement Scheduling To Accelerate Fault-Tolerant Quantum Programs

Abstract

Fault-tolerant quantum computers run millions of logical cycles to perform quantum error correction (QEC). As logical operations span entire logical cycles, the logical cycle time (LCT) dictates program runtime. Qubit measurements, critical to extract parity information for QEC, are the slowest operations and account for 43-86% of LCT. Measurement latencies impact fidelity: fast measurements lower our ability to correctly classify quantum states, whereas slow measurements increase the likelihood of decoherence. Hardware providers thus calibrate measurement latencies that maximize readout fidelity per qubit and use them to schedule all measurements during program execution. However, calibrated latencies are sub-optimal for logical performance because logical cycles span multiple QEC rounds, during which data qubits are not measured. This increases LCT and logical error rates (LERs) due to decoherence at the logical level. We propose DynaMite, a lightweight real-time measurement latency selection policy built on two key insights. First, logical cycles must use a measurement latency that is fast enough to reduce both LCT and LER for the QEC code, instead of the calibrated latency that only maximizes readout fidelity. Second, not all logical cycles are equal; many do not fully utilize the error budget of the QEC code, i.e., the number of failed parity checks it can tolerate without compromising LER. These cycles could use even faster measurements but do not, because latencies are chosen statically, whereas error information is only available at runtime. DynaMite exploits the fact that a logical cycle comprises multiple QEC rounds and selects the fastest latency for an upcoming round based on the error budget left and rounds remaining. Our evaluations show that DynaMite reduces LCT by 1.69x on average and up to 2.29x, and reduces LER to 0.46x on average and up to 0.13x of baseline.