def test_sycamore_decomposer_reject_0_controlled():
c = cirq.Circuit(cirq.X(a1).controlled_by(a2, control_values=[0]))
decomposer = ct.SycamoreDecomposer()
with pytest.raises(ct.DeviceMappingError):
decomposer.optimize_circuit(c)
def sample_with_ancilla(
self, num_samples: int) -> Tuple[List[int], List[Dict[str, int]]]:
"""Samples the board and returns square and ancilla measurements.
Sends the current circuit to the sampler then retrieves the results.
May return less samples than num_samples due to post-selection.
Returns the results as a tuple. The first entry is the list of
measured squares, as represented by a 64-bit int bitboard.
The second value is a list of ancilla values, as represented as a
dictionary from ancilla name to value (0 or 1).
"""
t0 = time.perf_counter()
measure_circuit = self.circuit.copy()
ancilla = []
error_count = 0
noise_count = 0
post_count = 0
if self.entangled_squares:
qubits = sorted(self.entangled_squares)
measure_moment = cirq.Moment(
cirq.measure(q, key=q.name) for q in qubits)
measure_circuit.append(measure_moment)
# Try to guess the appropriate number of repetitions needed
# Assume that each post_selection is about 50/50
# Noise and error mitigation will discard reps, so increase
# the total number of repetitions to compensate
if len(self.post_selection) > 1:
num_reps = num_samples * (2**(len(self.post_selection) + 1))
else:
num_reps = num_samples
if self.error_mitigation == enums.ErrorMitigation.Correct:
num_reps *= 2
noise_threshold = self.noise_mitigation * num_samples
if self.noise_mitigation > 0:
num_reps *= 3
if num_reps < 100:
num_reps = 100
self.debug_log += (f'Running circuit with {num_reps} reps '
f'to get {num_samples} samples:\n'
f'{str(measure_circuit)}\n')
# Translate circuit to grid qubits and sqrtISWAP gates
if self.device is not None:
# Decompose 3-qubit operations
ct.SycamoreDecomposer().optimize_circuit(measure_circuit)
# Create NamedQubit to GridQubit mapping and transform
measure_circuit = self.transformer.transform(measure_circuit)
# For debug, ensure that the circuit correctly validates
self.device.validate_circuit(measure_circuit)
# Run the circuit using the provided sampler (simulator or hardware)
results = self.sampler.run(measure_circuit, repetitions=num_reps)
# Parse the results
rtn = []
noise_buffer = {}
data = results.data
for rep in range(num_reps):
new_sample = self.state
new_ancilla = {}
# Go through the results and discard any results
# that disagree with our pre-defined post-selection criteria
post_selected = True
for qubit in self.post_selection.keys():
key = qubit.name
if key in data.columns:
result = data.at[rep, key]
if result != self.post_selection[qubit]:
post_selected = False
if not post_selected:
post_count += 1
continue
# Translate qubit results into a 64-bit chess board
for qubit in qubits:
key = qubit.name
result = data.at[rep, key]
# Ancilla bits should not be part of the chess board
if 'anc' not in key:
bit = qubit_to_bit(qubit)
new_sample = set_nth_bit(bit, new_sample, result)
else:
new_ancilla[key] = result
# Perform Error Mitigation
if self.error_mitigation != enums.ErrorMitigation.Nothing:
# Discard boards that have the wrong number of pieces
if num_ones(new_sample) not in self.allowed_pieces:
if self.error_mitigation == enums.ErrorMitigation.Error:
raise ValueError(
'Error detected, '
f'pieces allowed = {self.allowed_pieces}'
f'but got {num_ones(new_sample)}')
if self.error_mitigation == enums.ErrorMitigation.Correct:
error_count += 1
continue
# Noise mitigation
if self.noise_mitigation > 0.0:
# Ignore samples up to a threshold
if new_sample not in noise_buffer:
noise_buffer[new_sample] = 0
noise_buffer[new_sample] += 1
if noise_buffer[new_sample] < noise_threshold:
noise_count += 1
continue
# This sample has passed noise and error mitigation
# Record it as a proper sample
rtn.append(new_sample)
ancilla.append(new_ancilla)
if len(rtn) >= num_samples:
self.debug_log += (
f'Discarded {error_count} from error mitigation '
f'{noise_count} from noise and '
f'{post_count} from post-selection\n')
self.record_time('sample_with_ancilla', t0)
return (rtn, ancilla)
else:
rtn = [self.state] * num_samples
self.debug_log += (
f'Discarded {error_count} from error mitigation '
f'{noise_count} from noise and {post_count} from post-selection\n'
)
self.record_time("sample_with_ancilla", t0)
return (rtn, ancilla)