qiskit_addon_sqd.qubit.project_operator_to_subspace

project_operator_to_subspace(bitstring_matrix, hamiltonian, *, verbose=False)[source]

Projects a Pauli operator into a subspace.

The subspace is defined by a collection of computational basis states, which are specified by the bitstrings (rows) in bitstring_matrix.

Parameters:

  • bitstring_matrix (ndarray) – A 2D array of bool representations of bit values such that each row represents a single bitstring. This set of bitstrings specifies the subspace into which the hamiltonian will be projected and diagonalized.

  • hamiltonian (SparsePauliOp) – A Hamiltonian specified as a Pauli operator.

  • verbose (bool) – whether to print the stage of the subroutine.

Returns:

A scipy.sparse.coo_matrix representing the operator projected in the subspace.

Raises:

ValueError – Bitstrings (rows) in bitstring_matrix must have length < 64.

Return type:

spmatrix