Demonstrating real-time and low-latency quantum error correction with superconducting qubits

TL;DR

This paper demonstrates low-latency, real-time quantum error correction on superconducting qubits using FPGA decoding, achieving fast feedback and logical error suppression crucial for scalable fault-tolerant quantum computing.

Contribution

It introduces a scalable FPGA-based decoder with sub-microsecond latency, enabling real-time error correction on superconducting qubits and advancing towards fault-tolerant quantum computation.

Findings

Achieved decoding times below 1 microsecond per round

Demonstrated logical error suppression with increased decoding rounds

Implemented fast feedback with a response time of 9.6 microseconds

Abstract

Quantum error correction (QEC) will be essential to achieve the accuracy needed for quantum computers to realise their full potential. The field has seen promising progress with demonstrations of early QEC and real-time decoded experiments. As quantum computers advance towards demonstrating a universal fault-tolerant logical gate set, implementing scalable and low-latency real-time decoding will be crucial to prevent the backlog problem, avoiding an exponential slowdown and maintaining a fast logical clock rate. Here, we demonstrate low-latency feedback with a scalable FPGA decoder integrated into the control system of a superconducting quantum processor. We perform an 8-qubit stability experiment with up to $25$ decoding rounds and a mean decoding time per round below $1$ ${\mu}s$, 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 $9.6$ ${\mu}s$ 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.