From Round-Trip State Echo to Error Recovery: Snapshot-Resolved Quantum-Hardware Diagnostics
TL;DR
Quantum-hardware scores vary across workloads and execution times through repeated communication and deletion-recovery experiments on superconducting and trapped-ion hardware, and these measurements characterize complete compiled workloads at dated executions.
Abstract
Quantum-hardware scores vary across workloads and execution times. We study these variations through repeated communication and deletion-recovery experiments on superconducting and trapped-ion hardware. Our opening test is round-trip state echo (RTSE): prepare one of four tetrahedral qubit states, move it along a route and back by swaps, undo the preparation at the root, and measure the return probability. Repeating identical native communication programs on IQM Emerald changed the differences between tasks on the same routes, while the aggregate RTSE estimates differed by only $0.00125$. A separate two-window experiment found a drop in root return probability from route length 2 to 10 for both RTSE and its remote-inverse do-nothing predecessor; the prespecified directional test did not support better retention by RTSE. Across 64 fixed combinations of placement, input state, and deleted position, the IQM recovery mean fell from $0.738$ to $0.624$. On IonQ's five submitted virtual wires, with advertised all-to-all connectivity, recovery means of $0.911$ and $0.923$ exceeded the prespecified two-thirds reference in both windows. The corresponding differences from a control using the decoder's adjoint were $0.446$ and $0.443$. These measurements characterize complete compiled workloads at dated executions. Recovery is tested after subsystem discard in the circuit model, and each hardware interface is analyzed separately.