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arXiv · 1809.05057

Gate-efficient simulation of molecular eigenstates on a quantum computer

Marc Ganzhorn·Daniel J. Egger·Panagiotis Kl. Barkoutsos·Pauline Ollitrault·Gian Salis·Nikolaj Moll·Andreas Fuhrer·Peter Mueller·Stefan Woerner·Ivano Tavernelli·Stefan Filipp
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Abstract

A key requirement to perform simulations of large quantum systems on near-term quantum hardware is the design of quantum algorithms with short circuit depth that finish within the available coherence time. A way to stay within the limits of coherence is to reduce the number of gates by implementing a gate set that matches the requirements of the specific algorithm of interest directly in hardware. Here, we show that exchange-type gates are a promising choice for simulating molecular eigenstates on near-term quantum devices since these gates preserve the number of excitations in the system. Complementing the theoretical work by Barkoutsos et al. [PRA 98, 022322 (2018)], we report on the experimental implementation of a variational algorithm on a superconducting qubit platform to compute the eigenstate energies of molecular hydrogen. We utilize a parametrically driven tunable coupler to realize exchange-type gates that are configurable in amplitude and phase on two fixed-frequency superconducting qubits. With gate fidelities around 95% we are able to compute the eigenstates within an accuracy of 50 mHartree on average, a limit set by the coherence time of the tunable coupler.

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Marc Ganzhorn, Daniel J. Egger, Panagiotis Kl. Barkoutsos, Pauline Ollitrault, Gian Salis, Nikolaj Moll, Andreas Fuhrer, Peter Mueller, Stefan Woerner, Ivano Tavernelli, Stefan Filipp. 2018-09-13. Gate-efficient simulation of molecular eigenstates on a quantum computer. https://doi.org/10.1103/physrevapplied.11.044092

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