matrix_ops.to_density_matrix¶

Converts a row or a column vector to a density matrix.

Functions¶

to_density_matrix(input_array)

Convert a given vector to a density matrix or return the density matrix if already given.

Module Contents¶

matrix_ops.to_density_matrix.to_density_matrix(input_array)¶

Convert a given vector to a density matrix or return the density matrix if already given.

If the input is a vector, this function computes the outer product to form a density matrix. If the input is already a density matrix (square matrix), it returns the matrix as is.

Examples

As an example, consider one of the Bell states.

>>> from toqito.states import bell
>>> from toqito.matrix_ops import to_density_matrix
>>>
>>> to_density_matrix(bell(0))
array([[0.5, 0. , 0. , 0.5],
       [0. , 0. , 0. , 0. ],
       [0. , 0. , 0. , 0. ],
       [0.5, 0. , 0. , 0.5]])

Raises:: ValueError – If the input is not a vector or a square matrix.
Parameters:: input_array (numpy.ndarray) – Input array which could be a vector or a density matrix.
Returns:: The computed or provided density matrix.
Return type:: numpy.ndarray