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arXiv · 2607.22273

Unbiased Diffusion Monte Carlo for non local operators

Carlos Rodriguez Perez·Valerio Olevano·Francesco Sottile·Vitaly Gorelov
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Abstract

We propose a new mathematically exact method for computing unbiased Diffusion Monte Carlo (DMC) estimates of non-local operators. We demonstrate that the current state-of- the-art technique, Forward Walking, is only exact for local quantities and fails to yield unbiased results for the non-local components of reduced density matrices (RDMs). Our method significantly outperforms Forward Walking, as shown in two systems: in the symmetric Hubbard dimer it yields a pure 1RDM; while in the Helium atom it will give an unbiased 1RDM in the limits of zero time step and infinite walkers.

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Carlos Rodriguez Perez, Valerio Olevano, Francesco Sottile, Vitaly Gorelov. 2026-07-24. Unbiased Diffusion Monte Carlo for non local operators. https://arxiv.org/abs/2607.22273

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