Evaluating analytic gradients of pulse programs on quantum computers

Title: Evaluating analytic gradients of pulse programs on quantum computers
Speaker: Korbinian Kottmann from Xanadu
Abstract:
Parametrized pulse programs running on quantum hardware can be differentiated viathe stochastic parameter-shift (SPS) rule. We overcome the intrinsically approximatenature of SPS by introducing a new analytic method for computing gradients of pulseprograms, that we coin ODEgen [/oʊ-diː-dʒɛn/]. In this new method, we find effectivegenerators of pulse gates using a differentiable ordinary differential equation (ODE)solver. These effective generators inform parameter-shift rules that can be evaluatedon quantum hardware. We showcase simulated VQE examples with realistic superconducting transmon systems, for which we obtain lower energies with fewer quantumresources using ODEgen over SPS. We further demonstrate a pulse VQE run withgradients computed via ODEgen entirely on quantum hardware.
arXiv: arxiv.org/abs/2309.16756