def apply_noise_to_moments(
circuit: Circuit, noise: Iterable[Type[Noise]], target_qubits: QubitSet, position: str
) -> Circuit:
"""
Apply initialization/readout noise to the circuit.
When `noise.qubit_count` == 1, `noise` is added to all qubits in `target_qubits`.
When `noise.qubit_count` > 1, `noise.qubit_count` must be the same as the length of
`target_qubits`.
Args:
circuit (Circuit): A ciruit where `noise` is applied to.
noise (Iterable[Type[Noise]]): Noise channel(s) to be applied
to the circuit.
target_qubits (QubitSet): Index or indices of qubits. `noise` is applied to.
Returns:
Circuit: modified circuit.
"""
noise_instructions = []
for noise_channel in noise:
if noise_channel.qubit_count == 1:
new = [Instruction(noise_channel, qubit) for qubit in target_qubits]
noise_instructions = noise_instructions + new
else:
noise_instructions.append(Instruction(noise_channel, target_qubits))
new_moments = Moments()
if position == "initialization":
for noise in noise_instructions:
new_moments.add_noise(noise, "initialization_noise")
# add existing instructions
for moment_key in circuit.moments:
instruction = circuit.moments[moment_key]
# if the instruction is noise instruction
if isinstance(instruction.operator, Noise):
new_moments.add_noise(instruction, moment_key.moment_type, moment_key.noise_index)
# if the instruction is a gate instruction
else:
new_moments.add([instruction], moment_key.noise_index)
if position == "readout":
for noise in noise_instructions:
new_moments.add_noise(noise, "readout_noise")
circuit._moments = new_moments
return circuit
def apply_noise_to_gates(
circuit: Circuit,
noise: Iterable[Type[Noise]],
target_gates: Union[Iterable[Type[Gate]], np.ndarray],
target_qubits: QubitSet,
) -> Circuit:
"""Apply noise after target gates in target qubits.
When `noise.qubit_count` == 1, `noise` is applied to target_qubits after `target_gates`.
When `noise.qubit_count` > 1, all elements in `target_gates`, if is given, must have
the same number of qubits as `noise.qubit_count`.
Args:
circuit (Circuit): A ciruit where `noise` is applied to.
noise (Iterable[Type[Noise]]): Noise channel(s) to be applied
to the circuit.
target_gates (Union[Iterable[Type[Gate]], np.ndarray]): List of gates, or a unitary matrix
which `noise` is applied to.
target_qubits (QubitSet): Index or indices of qubits which `noise` is applied to.
Returns:
Circuit: modified circuit.
Raises:
Warning:
If `noise` is multi-qubit noise while there is no gate with the same
number of qubits in `target_qubits` or in the whole circuit when
`target_qubits` is not given.
If no `target_gates` exist in `target_qubits` or in the whole circuit
when `target_qubits` is not given.
"""
new_moments = Moments()
noise_applied = False
for moment_key in circuit.moments:
instruction = circuit.moments[moment_key]
# add the instruction to new_moments if it is noise instruction
if isinstance(instruction.operator, Noise):
new_moments.add_noise(instruction, moment_key.moment_type, moment_key.noise_index)
# if the instruction is a gate instruction
else:
new_noise_instruction = []
noise_index = moment_key.noise_index
if isinstance(target_gates, np.ndarray):
if (instruction.operator.name == "Unitary") and (
np.array_equiv(instruction.operator._matrix, target_gates)
):
intersection = list(set(instruction.target) & set(target_qubits))
(
new_noise_instruction,
noise_index,
noise_applied,
) = _apply_noise_to_gates_helper(
noise,
target_qubits,
instruction,
noise_index,
intersection,
noise_applied,
new_noise_instruction,
)
elif (target_gates is None) or (
instruction.operator.name in [g.__name__ for g in target_gates]
):
intersection = list(set(instruction.target) & set(target_qubits))
new_noise_instruction, noise_index, noise_applied = _apply_noise_to_gates_helper(
noise,
target_qubits,
instruction,
noise_index,
intersection,
noise_applied,
new_noise_instruction,
)
# add the gate and gate noise instructions to new_moments
new_moments.add([instruction], noise_index=noise_index)
for instruction, noise_index in new_noise_instruction:
new_moments.add_noise(instruction, "gate_noise", noise_index)
no_noise_applied_warning(noise_applied)
circuit._moments = new_moments
return circuit