rand.random_density_matrix
Generate random density matrix.
Module Contents
Functions
|
Generate a random density matrix. |
- rand.random_density_matrix.random_density_matrix(dim, is_real=False, k_param=None, distance_metric='haar')
Generate a random density matrix.
Generates a random
dim
-by-dim
density matrix distributed according to the Hilbert-Schmidt measure. The matrix is of rank <=k_param
distributed according to the distributiondistance_metric
Ifis_real = True
, then all of its entries will be real. The variabledistance_metric
must be one of:haar
(default):Generate a larger pure state according to the Haar measure and trace out the extra dimensions. Sometimes called the Hilbert-Schmidt measure when
k_param = dim
.
bures
:The Bures measure.
Examples
Using
toqito
, we may generate a random complex-valued \(n\)- dimensional density matrix. For \(d=2\), this can be accomplished as follows.>>> from toqito.rand import random_density_matrix >>> complex_dm = random_density_matrix(2) >>> complex_dm [[0.34903796+0.j 0.4324904 +0.103298j] [0.4324904 -0.103298j 0.65096204+0.j ]]
We can verify that this is in fact a valid density matrix using the
is_denisty
function fromtoqito
as follows>>> from toqito.matrix_props import is_density >>> is_density(complex_dm) True
We can also generate random density matrices that are real-valued as follows.
>>> from toqito.rand import random_density_matrix >>> real_dm = random_density_matrix(2, is_real=True) >>> real_dm [[0.37330805 0.46466224] [0.46466224 0.62669195]]
Again, verifying that this is a valid density matrix can be done as follows.
>>> from toqito.matrix_props import is_density >>> is_density(real_dm) True
By default, the random density operators are constructed using the Haar measure. We can select to generate the random density matrix according to the Bures metric instead as follows.
>>> from toqito.rand import random_density_matrix >>> bures_mat = random_density_matrix(2, distance_metric="bures") >>> bures_mat [[0.59937164+0.j 0.45355087-0.18473365j] [0.45355087+0.18473365j 0.40062836+0.j ]]
As before, we can verify that this matrix generated is a valid density matrix.
>>> from toqito.matrix_props import is_density >>> is_density(bures_mat) True
- Parameters:
dim (int) – The number of rows (and columns) of the density matrix.
is_real (bool) – Boolean denoting whether the returned matrix will have all real entries or not.
k_param (list[int] | int) – Default value is equal to
dim
.distance_metric (str) – The distance metric used to randomly generate the density matrix. This metric is either the Haar measure or the Bures measure. Default value is to use the Haar measure.
- Returns:
A
dim
-by-dim
random density matrix.- Return type:
numpy.ndarray