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Merged
merged 3 commits into from
Nov 27, 2023
Merged

Cleanup classical simulator code and fix a couple of bugs #6344

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59f0da8
Cleanup classical simulator code and fix a couple of bugs
NoureldinYosri Nov 13, 2023
8f3fde9
nit
NoureldinYosri Nov 13, 2023
83ef04d
Merge branch 'master' into classical_sim
NoureldinYosri Nov 27, 2023
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102 changes: 41 additions & 61 deletions cirq-core/cirq/sim/classical_simulator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,14 @@
import numpy as np


def _is_identity(op: ops.Operation) -> bool:
if isinstance(op.gate, (ops.XPowGate, ops.CXPowGate, ops.CCXPowGate, ops.SwapPowGate)):
return op.gate.exponent % 2 == 0
return False


class ClassicalStateSimulator(SimulatesSamples):
"""A simulator that only accepts only gates with classical counterparts.
"""A simulator that accepts only gates with classical counterparts.

This simulator evolves a single state, using only gates that output a single state for each
input state. The simulator runs in linear time, at the cost of not supporting superposition.
Expand All @@ -47,7 +53,9 @@ class ClassicalStateSimulator(SimulatesSamples):
A dictionary mapping measurement keys to measurement results.

Raises:
ValueError: If one of the gates is not an X, CNOT, SWAP, TOFFOLI or a measurement.
ValueError: If
- one of the gates is not an X, CNOT, SWAP, TOFFOLI or a measurement.
- A measurement key is used for measurements on different numbers of qubits.
"""

def _run(
Expand All @@ -60,68 +68,40 @@ def _run(

for moment in resolved_circuit:
for op in moment:
gate = op.gate
if gate == ops.X:
values_dict[op.qubits[0]] = 1 - values_dict[op.qubits[0]]

elif (
isinstance(gate, ops.CNotPowGate)
and gate.exponent == 1
and gate.global_shift == 0
):
if values_dict[op.qubits[0]] == 1:
values_dict[op.qubits[1]] = 1 - values_dict[op.qubits[1]]

elif (
isinstance(gate, ops.SwapPowGate)
and gate.exponent == 1
and gate.global_shift == 0
):
hold_qubit = values_dict[op.qubits[1]]
values_dict[op.qubits[1]] = values_dict[op.qubits[0]]
values_dict[op.qubits[0]] = hold_qubit

elif (
isinstance(gate, ops.CCXPowGate)
and gate.exponent == 1
and gate.global_shift == 0
):
if (values_dict[op.qubits[0]] == 1) and (values_dict[op.qubits[1]] == 1):
values_dict[op.qubits[2]] = 1 - values_dict[op.qubits[2]]

elif isinstance(gate, ops.MeasurementGate):
qubits_in_order = op.qubits
# add the new instance of a key to the numpy array in results dictionary
if gate.key in results_dict:
shape = len(qubits_in_order)
current_array = results_dict[gate.key]
new_instance = np.zeros(shape, dtype=np.uint8)
for bits in range(0, len(qubits_in_order)):
new_instance[bits] = values_dict[qubits_in_order[bits]]
results_dict[gate.key] = np.insert(
current_array, len(current_array[0]), new_instance, axis=1
if _is_identity(op):
continue
if op.gate == ops.X:
(q,) = op.qubits
values_dict[q] ^= 1
elif op.gate == ops.CNOT:
c, q = op.qubits
values_dict[q] ^= values_dict[c]
elif op.gate == ops.SWAP:
a, b = op.qubits
values_dict[a], values_dict[b] = values_dict[b], values_dict[a]
elif op.gate == ops.TOFFOLI:
c1, c2, q = op.qubits
values_dict[q] ^= values_dict[c1] & values_dict[c2]
elif protocols.is_measurement(op):
measurement_values = np.array(
[[[values_dict[q] for q in op.qubits]]] * repetitions, dtype=np.uint8
)
key = op.gate.key # type: ignore
if key in results_dict:
if op._num_qubits_() != results_dict[key].shape[-1]:
raise ValueError(
f'Measurement shape {len(measurement_values)} does not match '
f'{results_dict[key].shape[-1]} in {key}.'
)
results_dict[key] = np.concatenate(
(results_dict[key], measurement_values), axis=1
)
else:
# create the array for the results dictionary
new_array_shape = (repetitions, 1, len(qubits_in_order))
new_array = np.zeros(new_array_shape, dtype=np.uint8)
for reps in range(0, repetitions):
for instances in range(1):
for bits in range(0, len(qubits_in_order)):
new_array[reps][instances][bits] = values_dict[
qubits_in_order[bits]
]
results_dict[gate.key] = new_array

elif not (
(isinstance(gate, ops.XPowGate) and gate.exponent == 0)
or (isinstance(gate, ops.CCXPowGate) and gate.exponent == 0)
or (isinstance(gate, ops.SwapPowGate) and gate.exponent == 0)
or (isinstance(gate, ops.CNotPowGate) and gate.exponent == 0)
):
results_dict[key] = measurement_values
else:
raise ValueError(
"Can not simulate gates other than cirq.XGate, "
+ "cirq.CNOT, cirq.SWAP, and cirq.CCNOT"
f'{op} is not one of cirq.X, cirq.CNOT, cirq.SWAP, '
'cirq.CCNOT, or a measurement'
)

return results_dict
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