  Quantum computing is poised to solve practically useful problems which are
computationally intractable for classical supercomputers. However, the current
generation of quantum computers are limited by errors that may only partially
be mitigated by developing higher-quality qubits. Quantum error correction
(QEC) will thus be necessary to ensure fault tolerance. QEC protects the
logical information by cyclically measuring syndrome information about the
errors. An essential part of QEC is the decoder, which uses the syndrome to
compute the likely effect of the errors on the logical degrees of freedom and
provide a tentative correction. The decoder must be accurate, fast enough to
keep pace with the QEC cycle (e.g., on a microsecond timescale for
superconducting qubits) and with hard real-time system integration to support
logical operations. As such, real-time decoding is essential to realize
fault-tolerant quantum computing and to achieve quantum advantage. In this
work, we highlight some of the key challenges facing the implementation of
real-time decoders while providing a succinct summary of the progress to-date.
Furthermore, we lay out our perspective for the future development and provide
a possible roadmap for the field of real-time decoding in the next few years.
As the quantum hardware is anticipated to scale up, this perspective article
will provide a guidance for researchers, focusing on the most pressing issues
in real-time decoding and facilitating the development of solutions across
quantum and computer science.
