  We propose a technique for optimizing quantum programs by temporally
stretching pre-calibrated pulses. As an example, we modify a three-qubit
Toffoli gate implementation by using an off-the-shelf numerical optimization
algorithm to shorten the cross-resonance pulses in the sequence. Preliminary
quantum process tomography results suggest that our strategy sometimes halves a
Toffoli gate's error in practice, increasing process fidelity from around 60%
to around 80%. Unlike existing quantum control techniques, ours takes seconds
to converge, demonstrating its potential utility when incorporated into a
general-purpose compiler pass that improves both the time and the accuracy of
quantum programs.

Quantum Physics;Programming Languages