def _subsystem_apply_reference(state, channel, mask):
if isket(state):
state = ket2dm(state)
if isoper(channel):
full_oper = tensor([channel if mask[j]
else qeye(state.dims[0][j])
for j in range(len(state.dims[0]))])
return full_oper * state * full_oper.dag()
else:
# Go to Choi, then Kraus
# chan_mat = array(channel.data.todense())
choi_matrix = super_to_choi(channel)
vals, vecs = eig(choi_matrix.full())
vecs = list(map(array, zip(*vecs)))
kraus_list = [sqrt(vals[j]) * vec2mat(vecs[j])
for j in range(len(vals))]
# Kraus operators to be padded with identities:
k_qubit_kraus_list = product(kraus_list, repeat=sum(mask))
rho_out = Qobj(inpt=zeros(state.shape), dims=state.dims)
for operator_iter in k_qubit_kraus_list:
operator_iter = iter(operator_iter)
op_iter_list = [next(operator_iter).conj().T if mask[j]
else qeye(state.dims[0][j])
for j in range(len(state.dims[0]))]
full_oper = tensor(list(map(Qobj, op_iter_list)))
rho_out = rho_out + full_oper * state * full_oper.dag()
return Qobj(rho_out)
def _subsystem_apply_reference(state, channel, mask):
if isket(state):
state = ket2dm(state)
if isoper(channel):
full_oper = tensor([
channel if mask[j] else qeye(state.dims[0][j])
for j in range(len(state.dims[0]))
])
return full_oper * state * full_oper.dag()
else:
# Go to Choi, then Kraus
# chan_mat = array(channel.data.todense())
choi_matrix = super_to_choi(channel)
vals, vecs = eig(choi_matrix.full())
vecs = list(map(array, zip(*vecs)))
kraus_list = [
sqrt(vals[j]) * vec2mat(vecs[j]) for j in range(len(vals))
]
# Kraus operators to be padded with identities:
k_qubit_kraus_list = product(kraus_list, repeat=sum(mask))
rho_out = Qobj(inpt=zeros(state.shape), dims=state.dims)
for operator_iter in k_qubit_kraus_list:
operator_iter = iter(operator_iter)
op_iter_list = [
next(operator_iter) if mask[j] else qeye(state.dims[0][j])
for j in range(len(state.dims[0]))
]
full_oper = tensor(list(map(Qobj, op_iter_list)))
rho_out = rho_out + full_oper * state * full_oper.dag()
return Qobj(rho_out)
def test_SuperChoiSuper(self):
"""
Superoperator: Converting superoperator to Choi matrix and back.
"""
h_5 = rand_herm(5)
superoperator = propagator(h_5, scipy.rand(),
[create(5), destroy(5), jmat(2, 'z')])
choi_matrix = super_to_choi(superoperator)
test_supe = choi_to_super(choi_matrix)
assert_((test_supe - superoperator).norm() < 1e-12)
def test_ChoiKrausChoi(self):
"""
Superoperator: Converting superoperator to Choi matrix and back.
"""
h_5 = rand_herm(5)
superoperator = propagator(h_5, scipy.rand(),
[create(5), destroy(5), jmat(2, 'z')])
choi_matrix = super_to_choi(superoperator)
kraus_ops = choi_to_kraus(choi_matrix)
test_choi = kraus_to_choi(kraus_ops)
assert_((test_choi - choi_matrix).norm() < 1e-12)
def test_SuperChoiSuper(self):
"""
Superoperator: Converting superoperator to Choi matrix and back.
"""
h_5 = rand_herm(5)
superoperator = propagator(
h_5, scipy.rand(),
[create(5), destroy(5), jmat(2, 'z')])
choi_matrix = super_to_choi(superoperator)
test_supe = choi_to_super(choi_matrix)
assert_((test_supe - superoperator).norm() < 1e-12)
def test_ChoiKrausChoi(self):
"""
Superoperator: Converting superoperator to Choi matrix and back.
"""
h_5 = rand_herm(5)
superoperator = propagator(
h_5, scipy.rand(),
[create(5), destroy(5), jmat(2, 'z')])
choi_matrix = super_to_choi(superoperator)
kraus_ops = choi_to_kraus(choi_matrix)
test_choi = kraus_to_choi(kraus_ops)
assert_((test_choi - choi_matrix).norm() < 1e-12)
