UpCCGSD ansatz solver #372
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bmhowe23
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Dec 1, 2025
H 0-pyscf.chk
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I think these "H 0" files may have been accidental checkins? If so, could you please remove them from the PR?
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Yes, they were accidental. Removed!
DCO Remediation Commit for Rod Rofougaran <[email protected]> I, Rod Rofougaran <[email protected]>, hereby add my Signed-off-by to this commit: 0dc33ef I, Rod Rofougaran <[email protected]>, hereby add my Signed-off-by to this commit: 9e2b660 I, Rod Rofougaran <[email protected]>, hereby add my Signed-off-by to this commit: 3dc57c8 Signed-off-by: Rod Rofougaran <[email protected]>
Signed-off-by: Rod Rofougaran <[email protected]>
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This PR introduces a full UpCCGSD operator-pool and stataprep solver implementation, constructed analogously to the current UCCGSD implementation. I also added analogous Python and C++ tests.
The UpCCGSD ansatz is the UCC ansatz with generalized singles and paired doubles, as described in this paper: https://arxiv.org/pdf/1810.02327.
UpCCGSD is lower-depth variant of UCCGSD in which double excitations are restricted to paired electron transfers between spatial orbitals, following the UpCC (unitary paired coupled-cluster) construction. While less expressive than full UCCGSD, it retains generalized spin-preserving singles and the most physically relevant pair-correlation channels, substantially reducing circuit depth and parameter count. This makes UpCCGSD attractive for larger systems or hardware-constrained regimes where UCCGSD is too costly.
@poojarao8