Real-time and Low-latency Quantum Error Correction Experiment Part 2: Results

In this second part, we present results of decoding in real-time with the FPGA decoder integrated into Rigetti's control stack. We perform an 8-qubit stability experiment with up to 25 decoding rounds and a mean decoding time per round below 1 µs, showing that we avoid the backlog problem even on superconducting hardware with the strictest speed requirements. We observe logical error suppression as the number of decoding rounds is increased. We also implement and time a fast-feedback experiment demonstrating a decoding response time of 9.6 µs for a total of 9 measurement rounds. The decoder throughput and latency developed in this work, combined with continued device improvements, unlock the next generation of experiments that go beyond purely keeping logical qubits alive and into demonstrating building blocks of fault-tolerant computation, such as lattice surgery and magic state teleportation.