def test_decomposition(self, U, tol):
"""This test checks the function :func:`dec.rectangular_symmetric` for
various unitary matrices.
A given unitary (identity or random draw from Haar measure) is
decomposed using the function :func:`dec.rectangular_symmetric`
and the resulting beamsplitters are multiplied together.
Test passes if the product matches identity.
"""
nmax, mmax = U.shape
assert nmax == mmax
tlist, diags = dec.rectangular_symmetric(U)
qrec = np.identity(nmax)
for i in tlist:
qrec = dec.mach_zehnder(*i) @ qrec
qrec = np.diag(diags) @ qrec
assert np.allclose(U, qrec, atol=tol, rtol=0)
def test_unitary_validation(self):
"""Test that an exception is raised if not unitary"""
A = np.random.random([5, 5]) + 1j * np.random.random([5, 5])
with pytest.raises(ValueError, match="matrix is not unitary"):
dec.rectangular_symmetric(A)