In its first architecture paper, the AWS Center for Quantum Computing has described a theoretical blueprint for a fault-tolerant quantum computer.

The highly technical paper suggests a novel approach to quantum error correction, which reduces gate error rates by redundantly encoding information into a protected (or logical) qubit using many physical qubits.

Amazon Web Services currently does not have its own quantum computing system, but instead provides access to a number of systems on its cloud service Braket.

And now for a gross oversimplification, that is still too complex

Quantum Computing
– Sebastian Moss

"An error-corrected quantum computer will be able to execute complex quantum algorithms despite noisy hardware that is prone to errors," the AWS researchers wrote in a post announcing their findings.

"The caveat, though, is that implementing quantum error correction at scale is a monumental scientific and engineering challenge, and the quantum computing field is still in the early stages of development. In particular, the resource overhead of popular approaches such as the surface code are very large, requiring hundreds to thousands of physical qubits for every encoded logical qubit."

The new architecture would instead encode information using 'cat qubits,' where the qubits are kept in quantum superpositions of coherent states with opposite phases.

On the hardware side, it would use a system of acoustic resonators coupled to superconducting circuits with a two-dimensional layout.

"It is based on hybrid acoustic-electro devices to implement a stabilized cat code with highly biased noise, dominated by dephasing," the paper says. "This cat code is then concatenated with an outer code that focuses mostly on correcting the dephasing errors. Our estimated overheads for performing fault-tolerant quantum algorithms showcase the promise of this approach."

The quantum computing system was not built, but simulated on AWS' conventional cloud.

"There are several interesting directions for future work to improve on our current proposal," the researchers said.