Computational Quantum Science Lab retuiteado
Excited to share our latest quantum chemistry preprint @cqs_lab, the result of the hard work of Clemens Giuliani, arxiv.org/abs/2503.14502. We use a "simple" variational wavefunction composed of a few hundred optimized non-orthogonal Slater determinants and show that it achieves energy accuracies comparable to state-of-the-art methods.
While the ansatz itself is as old as quantum chemistry, optimizing it fully has proven challenging so far. The main innovation is an approach to optimize the determinants efficiently, leveraging the quadratic dependence of energy on selected parameters, allowing for exact optimization. Using optimized contractions, it has scaling computational cost with the fourth power of the number of basis functions.
Benchmarking against exact full-configuration interaction results, we achieved lower variational energies than CCSD(T) for several molecules in the double-zeta basis.
It is more accurate than all second-quantized NQS results for molecules so far published, despite being a much simpler ansatz, conceptually. This, in my view, further highlights the fact that for the quantum chemistry of small to intermediate molecules fully correlated wave functions might not be necessarily needed.
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