Long-time simulations with high fidelity on quantum hardware

• URL: http://arxiv.org/abs/2102.04313v1
• Date: Mon, 8 Feb 2021 16:18:50 GMT
• Title: Long-time simulations with high fidelity on quantum hardware
• Authors: Joe Gibbs, Kaitlin Gili, Zo\"e Holmes, Benjamin Commeau, Andrew Arrasmith, Lukasz Cincio, Patrick J. Coles and Andrew Sornborger
• Abstract summary: We show that it is possible to implement long-time, high fidelity simulations on current hardware. Specifically, we simulate an XY-model spin chain on the Rigetti and IBM quantum computers. This is a factor of 150 longer than is possible using the iterated Trotter method.
• Score: 1.8909337252764988
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Moderate-size quantum computers are now publicly accessible over the cloud, opening the exciting possibility of performing dynamical simulations of quantum systems. However, while rapidly improving, these devices have short coherence times, limiting the depth of algorithms that may be successfully implemented. Here we demonstrate that, despite these limitations, it is possible to implement long-time, high fidelity simulations on current hardware. Specifically, we simulate an XY-model spin chain on the Rigetti and IBM quantum computers, maintaining a fidelity of at least 0.9 for over 600 time steps. This is a factor of 150 longer than is possible using the iterated Trotter method. Our simulations are performed using a new algorithm that we call the fixed state Variational Fast Forwarding (fsVFF) algorithm. This algorithm decreases the circuit depth and width required for a quantum simulation by finding an approximate diagonalization of a short time evolution unitary. Crucially, fsVFF only requires finding a diagonalization on the subspace spanned by the initial state, rather than on the total Hilbert space as with previous methods, substantially reducing the required resources.

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