2019/10/31 by Cristina Cirstoiu, Zoe Holmes, Joseph Iosue +3 · 1 citation
Physics and Astronomy · #quant-ph
paper · pdf · doi:10.1038/s41534-020-00302-0
published as npj Quantum Information 6, 82 (2020) · 13 + 7 pages, 7 figures
arxiv created 2020/09/19 · arxiv updated 2020/09/22
Trotterization-based, iterative approaches to quantum simulation are restricted to simulation times less than the coherence time of the quantum computer, which limits their utility in the near term. Here, we present a hybrid quantum-classical algorithm, called Variational Fast Forwarding (VFF), for decreasing the quantum circuit depth of quantum simulations. VFF seeks an approximate diagonalization of a short-time simulation to enable longer-time simulations using a constant number of gates. Our error analysis provides two results: (1) the simulation error of VFF scales at worst linearly in the fast-forwarded simulation time, and (2) our cost function's operational meaning as an upper bound on average-case simulation error provides a natural termination condition for VFF. We implement VFF for the Hubbard, Ising, and Heisenberg models on a simulator. Additionally, we implement VFF on Rigetti's quantum computer to demonstrate simulation beyond the coherence time. Finally, we show how to estimate energy eigenvalues using VFF.