How large does a useful quantum computer need to be?

This is an important but surprisingly hard question to answer.

Photonic qubits have the great advantage that they don’t easily interact with their environment and hence are intrinsically less noisy than many other qubit types…

There’s an unsung impasse currently facing commercially useful fault-tolerant quantum computers. Useful quantum computers rely on quantum error-correcting codes that redundantly encode otherwise delicate logical information into a much larger system of physical qubits….

We recently announced a new approach to vastly increasing the efficiency of running quantum algorithms. We call it the Active Volume Architecture. The key insight is that if you have access to certain hardware capabilities then you can obtain remarkable reductions in the running costs of commercially useful quantum algorithms (for example, reducing running costs by around 50x for factoring algorithms).

This technique specifically targets algorithms for error-corrected quantum computers, as opposed to non-error-corrected NISQ systems. ‘Active volume compilation’ reduces the time taken to run a given application, through more efficient use of the available hardware.

We’re excited that our work on Fusion Based Quantum Computing (FBQC) has recently been published in nature communications…