def one_qubit_dm(self, qstate, i):
'''
Returns subsystem density
matrix for qubit i by tracing out
all other qubits in `qstate`.
`qstate` needs to be in *full* qubit space!
'''
assert qstate.size == qu.prod(self._sim_dims)
return qu.ptr(qstate, dims=self._sim_dims, keep=i)
def psi_mb_ab_mat():
return np.concatenate(
[rand_ket(prod(DIMS_MB[:7])) for _ in range(6)],
axis=1)
def psi_mb_ab():
return rand_ket(prod(DIMS_MB[:7]))
def psi_mb_abc():
return rand_ket(prod(DIMS_MB))
def psi_ab_mat():
return np.concatenate(
[rand_ket(prod(DIMS[:-1])) for _ in range(6)],
axis=1)
def psi_ab():
return rand_ket(prod(DIMS[:-1]))
def psi_abc():
return rand_ket(prod(DIMS))
def test_lazy_ptr_dot_mat_simple(self, psi_abc, psi_ab_mat):
rho_ab = psi_abc.ptr(DIMS, [0, 1])
psi_out_expected = rho_ab @ psi_ab_mat
psi_out_got = lazy_ptr_dot(psi_abc, psi_ab_mat)
assert psi_out_got.shape == (prod(DIMS[:-1]), 6)
assert_allclose(psi_out_expected, psi_out_got)
def test_partial_trace_multi_ket(self):
dims = [2, 3, 4]
a = np.random.randn(qu.prod(dims), 1)
for i1, i2 in itertools.combinations([0, 1, 2], 2):
b = qu.partial_trace(a, dims, [i1, i2])
assert (b.shape[1] == dims[i1] * dims[i2])
def test_partial_trace_single_ket(self):
dims = [2, 3, 4]
a = np.random.randn(qu.prod(dims), 1)
for i, dim in enumerate(dims):
b = qu.partial_trace(a, dims, i)
assert (b.shape[0] == dim)
def test_permute_sparse_op(self):
dims = [3, 2, 5, 4]
a = qu.rand_rho(qu.prod(dims), sparse=True, density=0.5)
b = qu.permute(a, dims, [3, 1, 2, 0])
c = qu.permute(a.A, dims, [3, 1, 2, 0])
assert_allclose(b.A, c)
def test_permute_sparse_ket(self):
dims = [3, 2, 5, 4]
a = rand_ket(prod(dims), sparse=True, density=0.5)
b = permute(a, dims, [3, 1, 2, 0])
c = permute(a.A, dims, [3, 1, 2, 0])
assert_allclose(b.A, c)
