%0 Journal Article %D 2019 %T Site-by-site quantum state preparation algorithm for preparing vacua of fermionic lattice field theories %A Ali Hamed Moosavian %A James R. Garrison %A Stephen P. Jordan %X

Answering whether quantum computers can efficiently simulate quantum field theories has both theoretical and practical motivation. From the theoretical point of view, it answers the question of whether a hypothetical computer that utilizes quantum field theory would be more powerful than other quantum computers. From the practical point of view, when reliable quantum computers are eventually built, these algorithms can help us better understand the underlying physics that govern our world. In the best known quantum algorithms for simulating quantum field theories, the time scaling is dominated by initial state preparation. In this paper, we exclusively focus on state preparation and present a heuristic algorithm that can prepare the vacuum of fermionic systems in more general cases and more efficiently than previous methods. With our method, state preparation is no longer the bottleneck, as its runtime has the same asymptotic scaling with the desired precision as the remainder of the simulation algorithm. We numerically demonstrate the effectiveness of our proposed method for the 1+1 dimensional Gross-Neveu model.

%8 2019/11/8 %G eng %U https://arxiv.org/abs/1911.03505 %0 Journal Article %J Physical Review Letters %D 2017 %T Fast State Transfer and Entanglement Renormalization Using Long-Range Interactions %A Zachary Eldredge %A Zhe-Xuan Gong %A Ali Hamed Moosavian %A Michael Foss-Feig %A Alexey V. Gorshkov %X

In short-range interacting systems, the speed at which entanglement can be established between two separated points is limited by a constant Lieb-Robinson velocity. Long-range interacting systems are capable of faster entanglement generation, but the degree of the speed-up possible is an open question. In this paper, we present a protocol capable of transferring a quantum state across a distance L in d dimensions using long-range interactions with strength bounded by 1/rα. If α<d, the state transfer time is asymptotically independent of L; if α=d, the time is logarithmic in distance L; if d<α<d+1, transfer occurs in time proportional to Lαd; and if αd+1, it occurs in time proportional to L. We then use this protocol to upper bound the time required to create a state specified by a MERA (multiscale entanglement renormalization ansatz) tensor network, and show that, if the linear size of the MERA state is L, then it can be created in time that scales with L identically to state transfer up to multiplicative logarithmic corrections.

%B Physical Review Letters %V 119 %P 170503 %8 2017/10/25 %G eng %U https://arxiv.org/abs/1612.02442 %N 17 %R 10.1103/PhysRevLett.119.170503