High-fidelity quantum control by polychromatic pulse trains
We introduce a quantum control technique using polychromatic pulse sequences
(PPS), consisting of pulses with different carrier frequencies, i.e. different
detunings with respect to the qubit transition frequency. We derive numerous
PPS, which generate broadband, narrowband, and passband excitation profiles for
different target transition probabilities. This makes it possible to create
high-fidelity excitation profiles which are either (i) robust to deviations in
the experimental parameters, which is attractive for quantum computing, or (ii)
more sensitive to such variations, which is attractive for cross talk
elimination and quantum sensing. The method is demonstrated experimentally
using one of IBM's superconducting quantum processors, in a very good agreement
between theory and experiment. These results demonstrate both the excellent
coherence properties of the IBM qubits and the accuracy, robustness and
flexibility of the proposed quantum control technique. They also show that the
detuning is as efficient control parameter as the pulse phase that is commonly
used in composite pulses. Hence the method opens a variety of perspectives for
quantum control in areas where phase manipulation is difficult or inaccurate.
Svetoslav S. Ivanov Boyan T. Torosov Nikolay V. Vitanov