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arXiv · 1604.07210

Time Evolution and Deterministic Optimisation of Correlator Product States

Vid Stojevic·Philip Crowley·Tanja Đurić·Callum Grey·Andrew Green
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Abstract

We study a restricted class of correlator product states (CPS) for a spin-half chain in which each spin is contained in just two overlapping plaquettes. This class is also a restriction upon matrix product states (MPS) with local dimension $2^n$ ($n$ being the size of the overlapping regions of plaquettes) equal to the bond dimension. We investigate the trade-off between gains in efficiency due to this restriction against losses in fidelity. The time-dependent variational principle formulated for these states is numerically very stable. Moreover, it shows significant gains in efficiency compared to the naively related matrix product states - the evolution or optimisation scales as $2^{3n}$ for the correlator product states versus $2^{4n}$ for the unrestricted matrix product state. However, much of this advantage is offset by a significant reduction in fidelity. Correlator product states break the local Hilbert space symmetry by the explicit selection of a local basis. We investigate this dependence in detail and formulate the broad principles under which correlator product states may be a useful tool. In particular, we find that scaling with overlap/bond order may be more stable with correlator product states allowing a more efficient extraction of critical exponents - we present an example in which the use of correlator product states is several orders of magnitude quicker than matrix product states.

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Vid Stojevic, Philip Crowley, Tanja Đurić, Callum Grey, Andrew Green. 2016-04-25. Time Evolution and Deterministic Optimisation of Correlator Product States. https://doi.org/10.1103/physrevb.94.165135

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