QContext: Context-Aware Decomposition for Quantum Gates*

We propose QContext, a new compiler structure that incorporates context-aware and topology-aware decompositions. The standard compilers typically use the same decomposition template when decomposing the same gates. Because of circuit equivalence rules and resynthesis, variants of a gate-decomposition template may exist. QContext exploits the circuit information and the hardware topology to select the gate variant that increases circuit optimization opportunities. QContext is aware of both the gate context and the target hardware topology. We study the basis-gate-level context-aware decomposition for Toffoli gates and the native-gate-level context-aware decomposition for CNOT gates. We also propose new templates for the Toffoli and CNOT gates. Our experiments on a benchmark set of problems show that QContext reduces the number of two-qubit gates and single-qubit gates as compared with the state-of-the-art approach.