def test_color666_mps_decoder_decode_small_codes_exact_approx():
code = Color666Code(5)
exact_decoder = Color666MPSDecoder()
approx_decoder = Color666MPSDecoder(chi=16)
identity = code.new_pauli()
# probabilities
prob_dist = BiasedDepolarizingErrorModel(bias=10).probability_distribution(probability=0.1)
# coset probabilities
exact_coset_ps, _ = exact_decoder._coset_probabilities(prob_dist, identity)
approx_coset_ps, _ = approx_decoder._coset_probabilities(prob_dist, identity)
print('#exact Pr(G)=', exact_coset_ps)
print('#approx Pr(G)=', approx_coset_ps)
assert all(_is_close(exact_coset_ps, approx_coset_ps, rtol=1e-11, atol=0)), (
'Coset probabilites do not satisfy exact Pr(G) ~= approx Pr(G)')
def test_color666_mps_decoder_decode_value():
# expected coset_ps
expected_coset_ps = (
mp.mpf('1.4290529991554288e-9'), # I
mp.mpf('2.1657729564075353e-13'), # X
mp.mpf('2.2541268663248664e-13'), # Y
mp.mpf('9.3780172173812118e-12'), # Z
)
code = Color666Code(7)
decoder = Color666MPSDecoder(chi=16)
# error
error = code.new_pauli()
error.site('X', (2, 1))
# error.site('Y', (3, 1), (4, 2), (7, 3), (9, 6))
error.site('Y', (7, 3))
error.site('Z', (6, 0), (3, 3), (7, 6))
# syndrome
syndrome = pt.bsp(error.to_bsf(), code.stabilizers.T)
# sample
sample = decoder.sample_recovery(code, syndrome)
print(sample)
# probabilities
prob_dist = DepolarizingErrorModel().probability_distribution(0.1)
# coset probabilities
coset_ps, _ = decoder._coset_probabilities(prob_dist, sample)
print('# expected Pr(G)=', expected_coset_ps)
print('# actual Pr(G)=', coset_ps)
assert all(_is_close(expected_coset_ps, coset_ps, rtol=1e-11, atol=0)), (
'Coset probabilites do not satisfy expected Pr(G) ~= Pr(G)')
def test_color666_mps_decoder_cosets_probability_triplet_optimisation():
code = Color666Code(5)
decoder = Color666MPSDecoder()
# probabilities
prob_dist = BiasedDepolarizingErrorModel(bias=10).probability_distribution(probability=0.1)
# coset probabilities for null Pauli
coset_i_ps, _ = decoder._coset_probabilities(prob_dist, code.new_pauli())
coset_x_ps, _ = decoder._coset_probabilities(prob_dist, code.new_pauli().logical_x())
coset_y_ps, _ = decoder._coset_probabilities(prob_dist, code.new_pauli().logical_x().logical_z())
coset_z_ps, _ = decoder._coset_probabilities(prob_dist, code.new_pauli().logical_z())
# expect Pr(iIG) ~= Pr(xXG)
assert _is_close(coset_i_ps[0], coset_x_ps[1], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iIG) ~= Pr(xXG)')
# expect Pr(iXG) ~= Pr(xIG)
assert _is_close(coset_i_ps[1], coset_x_ps[0], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iXG) ~= Pr(xIG)')
# expect Pr(iIG) ~= Pr(yYG)
assert _is_close(coset_i_ps[0], coset_y_ps[2], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iIG) ~= Pr(yYG)')
# expect Pr(iYG) ~= Pr(yIG)
assert _is_close(coset_i_ps[2], coset_y_ps[0], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iXG) ~= Pr(xIG)')
# expect Pr(iIG) ~= Pr(zZG)
assert _is_close(coset_i_ps[0], coset_z_ps[3], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iIG) ~= Pr(zZG)')
# expect Pr(iZG) ~= Pr(zIG)
assert _is_close(coset_i_ps[3], coset_z_ps[0], rtol=0, atol=0), (
'Coset probabilites do not satisfy Pr(iZG) ~= Pr(zIG)')
def test_color666_mps_decoder_sample_recovery(error_pauli):
error = error_pauli.to_bsf()
code = error_pauli.code
syndrome = pt.bsp(error, code.stabilizers.T)
recovery_pauli = Color666MPSDecoder.sample_recovery(code, syndrome)
recovery = recovery_pauli.to_bsf()
assert np.array_equal(pt.bsp(recovery, code.stabilizers.T), syndrome), (
'recovery {} does not give the same syndrome as the error {}'.format(recovery, error))
assert np.all(pt.bsp(recovery ^ error, code.stabilizers.T) == 0), (
'recovery ^ error ({} ^ {}) does not commute with stabilizers.'.format(recovery, error))
def test_color666_mps_decoder_cosets_probability_equivalence(sample_pauli_f, sample_pauli_g):
decoder = Color666MPSDecoder()
# probabilities
prob_dist = BiasedDepolarizingErrorModel(bias=10).probability_distribution(probability=0.1)
# coset probabilities
coset_f_ps, _ = decoder._coset_probabilities(prob_dist, sample_pauli_f)
coset_g_ps, _ = decoder._coset_probabilities(prob_dist, sample_pauli_g)
print('#Pr(fG)=', coset_f_ps)
print('#Pr(gG)=', coset_g_ps)
assert all(_is_close(coset_f_ps, coset_g_ps, rtol=1e-14, atol=0)), (
'Coset probabilites do not satisfy Pr(fG) ~= Pr(gG)')
def test_color666_mps_decoder_decode(error_pauli, chi, caplog):
with caplog.at_level(logging.WARN):
error = error_pauli.to_bsf()
code = error_pauli.code
syndrome = pt.bsp(error, code.stabilizers.T)
decoder = Color666MPSDecoder(chi=chi)
recovery = decoder.decode(code, syndrome)
assert np.array_equal(pt.bsp(recovery, code.stabilizers.T), syndrome), (
'recovery {} does not give the same syndrome as the error {}'.format(recovery, error))
assert np.all(pt.bsp(recovery ^ error, code.stabilizers.T) == 0), (
'recovery ^ error ({} ^ {}) does not commute with stabilizers.'.format(recovery, error))
assert len(caplog.records) == 0, 'Unexpected log messages: {}'.format(caplog.text)
def test_color666_mps_decoder_cosets_probability_inequality_biased_noise(chi, tol, rtol):
code = Color666Code(5)
decoder = Color666MPSDecoder(chi=chi, tol=tol)
# probabilities
prob_dist = BiasedDepolarizingErrorModel(bias=100).probability_distribution(0.1)
# coset probabilities for null Pauli
coset_ps, _ = decoder._coset_probabilities(prob_dist, code.new_pauli())
coset_i_p, coset_x_p, coset_y_p, coset_z_p = coset_ps
# expect Pr(IG) > Pr(YG) > Pr(XG) ~= Pr(ZG)
print()
print('Pr(IG){!r} > Pr(YG){!r} > Pr(XG){!r} ~= Pr(ZG){!r}. rtol={}'.format(
coset_i_p, coset_y_p, coset_x_p, coset_z_p, abs(coset_x_p - coset_z_p) / abs(coset_z_p)))
print('types: Pr(IG):{}, Pr(YG):{}, Pr(XG):{}, Pr(ZG):{}'.format(
type(coset_i_p), type(coset_y_p), type(coset_x_p), type(coset_z_p)))
assert coset_i_p > coset_y_p, 'Coset probabilites do not satisfy Pr(IG) > Pr(YG)'
assert coset_y_p > coset_x_p, 'Coset probabilites do not satisfy Pr(YG) > Pr(XG)'
assert coset_y_p > coset_z_p, 'Coset probabilites do not satisfy Pr(YG) > Pr(ZG)'
assert _is_close(coset_x_p, coset_z_p, rtol=rtol, atol=0), 'Coset probabilites do not satisfy Pr(XG) ~= Pr(ZG)'
def test_color666_mps2d_contract():
code = Color666Code(5)
sample = code.new_pauli().site('X', (3, 1)).site('Y',
(2, 2)).site('Z', (6, 4))
print()
print(code.ascii_art(pauli=sample))
prob_dist = DepolarizingErrorModel().probability_distribution(0.1)
tnc = Color666MPSDecoder.TNC()
tn = tnc.create_tn(prob_dist, sample)
result_forwards = tt.mps2d.contract(tn)
print('Forward contraction result: ', repr(result_forwards))
assert isinstance(result_forwards,
mp.mpf), 'Contracted tensor network is not an mp.mpf'
assert 0 <= result_forwards <= 1, 'Contracted tensor network not within bounds'
result_backwards = tt.mps2d.contract(tn, start=-1, step=-1)
print('Backward contraction result:', repr(result_backwards))
assert isinstance(result_backwards,
mp.mpf), 'Contracted tensor network is not an mp.mpf'
assert 0 <= result_backwards <= 1, 'Contracted tensor network not within bounds'
assert _is_close(result_forwards, result_backwards, rtol=1e-14, atol=0), (
'Contracting forwards does not give the same result as contracting backwards'
)
def test_color666_mps_functions():
prob_dist = DepolarizingErrorModel().probability_distribution(0.1)
tnc = Color666MPSDecoder.TNC()
bra = [
tnc.create_q_node(prob_dist, ('I', 'I'), 'nw'),
tnc.create_s_node('w'),
tnc.create_q_node(prob_dist, ('I', None), 'sw'),
]
mpo1 = [
tnc.create_s_node('n'),
tnc.create_q_node(prob_dist, ('I', 'I'), 's'),
None,
]
mpo2 = [
tnc.create_q_node(prob_dist, (None, 'I'), 'ne'),
tnc.create_s_node('s'),
None,
]
ket = [
None,
tnc.create_q_node(prob_dist, ('I', None), 'e'),
None,
]
expected = 0.47831585185185249
# exact contraction for expected
result = tt.mps.contract_pairwise(bra, mpo1)
result = tt.mps.contract_pairwise(result, mpo2)
result = tt.mps.inner_product(result, ket)
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Exact contraction not as expected'
# exact contraction with contract_ladder
result = tt.mps.contract_pairwise(bra, mpo1)
result = tt.mps.contract_pairwise(result, mpo2)
result = tt.mps.contract_pairwise(result, ket)
result = tt.mps.contract_ladder(result)[0, 0, 0, 0]
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Exact contraction not as expected'
# exact contraction with lcf
result = tt.mps.left_canonical_form(bra)
result = tt.mps.contract_pairwise(result, mpo1)
result = tt.mps.left_canonical_form(result)
result = tt.mps.contract_pairwise(result, mpo2)
result = tt.mps.left_canonical_form(result)
result = tt.mps.inner_product(result, ket)
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Exact contraction with lcf not as expected'
# exact contraction with rcf
result = tt.mps.right_canonical_form(bra)
result = tt.mps.contract_pairwise(result, mpo1)
result = tt.mps.right_canonical_form(result)
result = tt.mps.contract_pairwise(result, mpo2)
result = tt.mps.right_canonical_form(result)
result = tt.mps.inner_product(result, ket)
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Exact contraction with rcf not as expected'
# exact contraction with truncate
result = tt.mps.contract_pairwise(bra, mpo1)
result, norm1 = tt.mps.truncate(result)
result = tt.mps.contract_pairwise(result, mpo2)
result, norm2 = tt.mps.truncate(result)
result = tt.mps.inner_product(result, ket)
result *= norm1 * norm2
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Exact contraction with truncate not as expected'
# exact contraction with normalise lcf
result, norm1 = tt.mps.left_canonical_form(bra, normalise=True)
result = tt.mps.contract_pairwise(result, mpo1)
result, norm2 = tt.mps.left_canonical_form(result, normalise=True)
result = tt.mps.contract_pairwise(result, mpo2)
result, norm3 = tt.mps.left_canonical_form(result, normalise=True)
result = tt.mps.inner_product(result, ket)
result *= norm1 * norm2 * norm3
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(
expected, result, rtol=1e-14,
atol=0), 'Exact contraction with normalise lcf not as expected'
# exact contraction with normalise rcf
result, norm1 = tt.mps.right_canonical_form(bra, normalise=True)
result = tt.mps.contract_pairwise(result, mpo1)
result, norm2 = tt.mps.right_canonical_form(result, normalise=True)
result = tt.mps.contract_pairwise(result, mpo2)
result, norm3 = tt.mps.right_canonical_form(result, normalise=True)
result = tt.mps.inner_product(result, ket)
result *= norm1 * norm2 * norm3
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(
expected, result, rtol=1e-14,
atol=0), 'Exact contraction with normalise rcf not as expected'
# approximate contraction with truncate (chi)
result = tt.mps.contract_pairwise(bra, mpo1)
result, norm1 = tt.mps.truncate(result, chi=4)
result = tt.mps.contract_pairwise(result, mpo2)
result, norm2 = tt.mps.truncate(result, chi=4)
result = tt.mps.inner_product(result, ket)
result *= norm1 * norm2
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(
expected, result, rtol=1e-14,
atol=0), 'Approx. contraction with truncate (chi) not as expected'
# approximate contraction with truncate (tol)
result = tt.mps.contract_pairwise(bra, mpo1)
result, norm1 = tt.mps.truncate(result, tol=1e-8)
result = tt.mps.contract_pairwise(result, mpo2)
result, norm2 = tt.mps.truncate(result, tol=1e-8)
result = tt.mps.inner_product(result, ket)
result *= norm1 * norm2
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(
expected, result, rtol=1e-14,
atol=0), 'Approx. contraction with truncate (tol) not as expected'
# reversed exact contraction for expected
result = tt.mps.contract_pairwise(mpo2, ket)
result = tt.mps.contract_pairwise(mpo1, result)
result = tt.mps.inner_product(bra, result)
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14,
atol=0), 'Reversed exact contraction not as expected'
# reversed approximate contraction with truncate (chi)
result = tt.mps.contract_pairwise(mpo2, ket)
result, norm1 = tt.mps.truncate(result, chi=4)
result = tt.mps.contract_pairwise(mpo1, result)
result, norm2 = tt.mps.truncate(result, chi=4)
result = tt.mps.inner_product(bra, result)
result *= norm1 * norm2
print('#result=', result, '#rtol=', abs(result - expected) / abs(expected))
assert _is_close(expected, result, rtol=1e-14, atol=0), (
'Reversed approx. contraction with truncate (chi) not as expected')
class _FixedDecoder(Decoder):
def __init__(self, decoding):
self.decoding = decoding
def decode(self, code, syndrome, **kwargs):
return self.decoding
@property
def label(self):
return 'fixed'
@pytest.mark.parametrize('code, error_model, decoder', [
# each code with each valid decoder
(Color666Code(5), DepolarizingErrorModel(), Color666MPSDecoder(chi=8)),
(FiveQubitCode(), DepolarizingErrorModel(), NaiveDecoder()),
(PlanarCode(5, 5), DepolarizingErrorModel(), PlanarCMWPMDecoder()),
(PlanarCode(5, 5), DepolarizingErrorModel(), PlanarMPSDecoder(chi=6)),
(PlanarCode(5, 5), DepolarizingErrorModel(), PlanarMWPMDecoder()),
(PlanarCode(5, 5), DepolarizingErrorModel(), PlanarRMPSDecoder(chi=6)),
(PlanarCode(4, 5), BitPhaseFlipErrorModel(), PlanarYDecoder()),
(RotatedPlanarCode(7, 7), DepolarizingErrorModel(), RotatedPlanarMPSDecoder(chi=8)),
(RotatedPlanarCode(7, 7), DepolarizingErrorModel(), RotatedPlanarRMPSDecoder(chi=8)),
(RotatedPlanarCode(7, 7), BiasedDepolarizingErrorModel(100), RotatedPlanarSMWPMDecoder()),
(RotatedToricCode(6, 6), BiasedDepolarizingErrorModel(100), RotatedToricSMWPMDecoder()),
(SteaneCode(), DepolarizingErrorModel(), NaiveDecoder()),
(ToricCode(5, 5), DepolarizingErrorModel(), ToricMWPMDecoder()),
# each generic noise model
(PlanarCode(5, 5), BiasedDepolarizingErrorModel(10), PlanarMPSDecoder(chi=6)),
(PlanarCode(5, 5), BiasedYXErrorModel(10), PlanarMPSDecoder(chi=6)),
def test_color666_mps_decoder_new_invalid_parameters(chi, tol):
with pytest.raises((ValueError, TypeError), match=r"^Color666MPSDecoder") as exc_info:
Color666MPSDecoder(chi=chi, tol=tol)
print(exc_info)
def test_color666_mps_decoder_new_valid_parameters(chi, tol):
Color666MPSDecoder(chi=chi, tol=tol) # no error raised
def test_color666_mps_decoder_properties():
decoder = Color666MPSDecoder(chi=8, tol=1e-8)
assert isinstance(decoder.label, str)
assert isinstance(repr(decoder), str)
assert isinstance(str(decoder), str)