Estimating the cost to run quantum circuits by parallelizing surface code operations

What is it about?

We upgrade an open-source compiler for surface code quantum computing to enable it to parallelize primitive operations, allowing a more realistic cost analysis for the execution of large quantum circuits than what had previously been done. We also show how using many parallel magic state factories can drive down overall costs.

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Why is it important?

The protocol that we use for compiling quantum circuits into primitive surface code operations preserves the parallelism of the original circuit within the fault-tolerant layer. This is different from the most popular protocol which destroys circuits' parallelizability in order to eliminate a certain class of gates. We demonstrate how to realistically estimate quantum circuit execution costs within this framework, and our results suggest that our scheme lowers resource requirements for large, highly parallel input circuits.