Compensating for bandwidth limitations in radio-frequency control waveforms

Presenting Author: Kevin Kuper, University of Arizona
Contributing Author(s): Nathan Lysne, Poul Jessen

Exercising accurate control over quantum systems is necessary for quantum computation and analog quantum simulation. As our ability to control these systems continues to improve, new limitations inherent in the specific control toolbox used can surface. On our testbed of electronic ground state Cs atoms, we have improved our control over the atoms’ spin states to a point where bandwidth and slew-rate limitations on the control fields have a noticeable impact on the control fidelity. So far, we numerically search for control waveforms using a gradient ascent algorithm to optimize control fidelity, with piecewise constant phases of the control fields serving as control variables. This greatly reduces the computational overhead, but results in waveform discontinuities that cannot be faithfully reproduced in the laboratory. Assuming linear response in our chain of amplifiers and magnet coils, the actual magnetic field waveform is given by the convolution of the input waveform with a response function that can be independently measured. This poster discusses possible methods for improving the control fidelity, with special attention given to designing input waveforms that limit or correct for the effects of finite bandwidth and/or slew-rate.

(Session 5 : Thursday from 5:00pm - 7:00 pm)


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