Curator's Take
This article shows how adding a Bell‑pair layer to standard mirror randomized benchmarking yields “Mirror Quantum Awesomeness,” a protocol that can monitor two‑qubit error correlations across an entire processor while still reporting a global infidelity. By pinpointing a depth of roughly 50 gates on IBM’s 156‑qubit devices where simple mitigation breaks down, the work gives hardware teams a concrete benchmark for when more sophisticated error‑correcting techniques—such as surface‑code decoders used in the topological variant—become necessary. The approach bridges routine performance testing and early‑stage fault‑tolerance diagnostics, offering a practical tool for scaling quantum processors beyond today’s noisy intermediate‑scale era.
— Mark Eatherly
Summary
Mirror randomized benchmarking (MRB) is an established technique that provides a global error metric at the scale of a whole QPU. To expand upon this we introduce Mirror Quantum Awesomeness (MQA), a hybrid protocol that adds a structured entangling layer to MRB circuits. This enables per-edge correlation dynamics to be tracked via mutual information while preserving the MRB infidelity estimate. The resulting analysis of the injected entangled pairs locates a critical circuit depth, beyond which rudimentary error mitigation techniques can be expected to fail. A topological variant, Topological MQA, supplies a second critical depth via a decoder based on the surface-code decoding problem. Both are validated in simulation and demonstrated on the 156-qubit \texttt{ibm\_fez} and \texttt{ibm\_kingston} processors, where MQA closely agrees with MRB on the entanglement infidelity and the critical depth for \texttt{ibm\_fez} is found to be $\sim 50$.