def serial_executor(circuit: QPROGRAM, noise: float = BASE_NOISE) -> float:
"""A noisy executor function which executes the input circuit with `noise`
depolarizing noise and returns the expectation value of the ground state
projector. Simulation will be slow for "large circuits" (> a few qubits).
"""
circuit, _ = convert_to_mitiq(circuit)
# Ground state projector.
d = 2**len(circuit.all_qubits())
obs = np.zeros(shape=(d, d), dtype=np.float32)
obs[0, 0] = 1.0
return noisy_simulation(circuit, noise, obs)
def executor(circuit: QPROGRAM,
noise_level: float = 0.1,
shots: int = 8192) -> MeasurementResult:
"""Returns computational basis measurements after executing the circuit
with depolarizing noise.
Args:
circuit: Circuit to execute.
noise_level: Probability of depolarizing noise after each moment.
shots: Number of samples to take.
Returns:
Dictionary where each key is a bitstring (binary int) and each value
is the number of times that bitstring was measured.
"""
circuit = circuit.with_noise(cirq.depolarize(p=noise_level))
circuit.append(cirq.measure(*circuit.all_qubits(), key="z"))
result = cirq.DensityMatrixSimulator().run(circuit, repetitions=shots)
return {bin(k): v for k, v in result.histogram(key="z").items()}