oqp.quantum.fcidump
Read and write the FCIDUMP interchange format.
FCIDUMP is the de-facto standard exchange format for the second-quantized
molecular electronic Hamiltonian
H = E_core
+ sum_{pq,s} h_{pq} a^+_{p,s} a_{q,s}
+ 1/2 sum_{pqrs,st} (pq|rs) a^+_{p,s} a^+_{r,t} a_{s,t} a_{q,s}
expressed over a set of (real, orthonormal) molecular spatial orbitals. It is
consumed directly by Qiskit Nature, OpenFermion (``MolecularData`` via
``from_pyscf``/FCIDUMP loaders), PySCF (``pyscf.tools.fcidump``), Block2/DMRG,
and most active-space / quantum-computing front ends, which makes it the
shortest path from an OpenQP mean-field calculation to a quantum-computing
workflow.
This module has no dependency on the compiled ``oqp`` extension.
Attributes
Functions
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Module Contents
- DEFAULT_TOLERANCE = 1e-12
- write_fcidump(filename, h1, h2, ecore, n_electrons, ms2=0, orbsym=None, isym=1, tol=DEFAULT_TOLERANCE)
Write a FCIDUMP file. :param filename: Output path. :type filename: str :param h1: One-electron MO integrals ``h_pq``. :type h1: array_like, shape (norb, norb) :param h2: Two-electron MO integrals ``(pq|rs)`` in chemist notation. :type h2: array_like, shape (norb, norb, norb, norb) :param ecore: Scalar (core / nuclear-repulsion + frozen-core) energy. :type ecore: float :param n_electrons: Number of correlated electrons. :type n_electrons: int :param ms2: ``2 * S_z`` (number of alpha minus beta electrons). Default 0. :type ms2: int :param orbsym: Per-orbital symmetry labels. Defaults to all-totally-symmetric (1). :type orbsym: sequence of int, optional :param isym: Spatial symmetry of the target state. :type isym: int :param tol: Integrals with magnitude at or below this are omitted. :type tol: float
- read_fcidump(filename)
Read a FCIDUMP file produced by :func:`write_fcidump` (or PySCF). Returns a dict with keys ``norb``, ``nelec``, ``ms2``, ``isym``, ``orbsym``, ``h1`` (norb, norb), ``h2`` (norb^4, chemist notation, fully symmetrized) and ``ecore``.