Tensor network utils

I/O functions for tensors and mps (list of tensors). Furthermore, the class QCOperators for handling operators is provided.

Functions and classes

class qmatchatea.utils.tn_utils.QCOperators[source]

Class to store and save to file operators. To add an operator to the list use self[‘op_name’] = op_tensor.

It starts with the pauli operators already defined, with keywords “X”,”Y”,”Z”

qmatchatea.utils.tn_utils.read_mps(filename, cmplx=True)[source]

Read an MPS from a given file. Reads in column-major order but the output is in row-major.

This function was used to exchange the MPS with the Fortran backend (thus the different ordering), which is now deprecated.

filename: str: PATH to the file
cmplx: bool, optional: If True the MPS is complex, real otherwise. Default to True

qmatchatea.utils.tn_utils.write_mps(filename, mps, cmplx=True)[source]

Write an MPS to file. The tensor is written in Fortran-like indexing, i.e. the MPS tensors will be converted from row-major into column-major order.

This function was used to exchange the MPS with the Fortran backend (thus the different ordering), which is now deprecated.

filename: str: PATH to the file
mps: list: List of tensors forming the mps
cmplx: bool, optional: If True the MPS is complex, real otherwise. Default to True

None

qmatchatea.utils.tn_utils.write_tensor(tensor, dest, cmplx=True, sparse=False)[source]

Write a tensor stored in a numpy matrix to a file. Conversion to column major is taken care of here.

Arguments

tensornp.ndarray: Tensor to be written to the file.
deststr, or filehandle: If string, file will be created or overwritten. If filehandle, then data will be written there.
sparse: bool: If True write the tensor in a sparse format, i.e. each row is written as idx elem where idx is the position of the element elem in the tensor vector