qiskit.providers.aer.noise.QuantumError

class QuantumError(noise_ops, number_of_qubits=None, standard_gates=True, atol=1e-08)

Quantum error class for Qiskit Aer noise model

WARNING: The init interface for this class is not finalized and may

change in future releases. For maximum backwards compatibility use the QuantumError generating functions in the noise.errors module.

Create a quantum error for a noise model.

Noise ops may either be specified as list of Kraus operators for a general CPTP map, or as a list of (circuit, p) pairs where circuit is a qobj circuit for the noise, and p is the probability of the error circuit. If the input is Kraus operators they will be converted to the circuit format, with checks applied for determining if any Kraus operators are unitary matrices.

Example

An example noise_ops for a bit-flip error with error probability p = 0.1 is:

noise_ops = [([{"name": "id", "qubits": 0}], 0.9),
             ([{"name": "x", "qubits": 0}], 0.1)]

The same error represented as a Kraus channel can be input as:

noise_ops = [np.sqrt(0.9) * np.array([[1, 0], [0, 1]]),
             np.sqrt(0.1) * np.array([[0, 1], [1, 0]])]

Parameters

• noise_ops (list) – A list of noise ops. See additional information.

• number_of_qubits (int) – specify the number of qubits for the error. If None this will be determined automatically (default None).

• standard_gates (bool) – Check if input matrices are standard gates.

• atol (double) – Threshold for testing if probabilities are equal to 0 or 1 (Default: 1e-8).

Raises

NoiseError – If input noise_ops are not a CPTP map.

__init__(noise_ops, number_of_qubits=None, standard_gates=True, atol=1e-08)

Create a quantum error for a noise model.

Noise ops may either be specified as list of Kraus operators for a general CPTP map, or as a list of (circuit, p) pairs where circuit is a qobj circuit for the noise, and p is the probability of the error circuit. If the input is Kraus operators they will be converted to the circuit format, with checks applied for determining if any Kraus operators are unitary matrices.

Example

An example noise_ops for a bit-flip error with error probability p = 0.1 is:

noise_ops = [([{"name": "id", "qubits": 0}], 0.9),
             ([{"name": "x", "qubits": 0}], 0.1)]

The same error represented as a Kraus channel can be input as:

noise_ops = [np.sqrt(0.9) * np.array([[1, 0], [0, 1]]),
             np.sqrt(0.1) * np.array([[0, 1], [1, 0]])]

Parameters

• noise_ops (list) – A list of noise ops. See additional information.

• number_of_qubits (int) – specify the number of qubits for the error. If None this will be determined automatically (default None).

• standard_gates (bool) – Check if input matrices are standard gates.

• atol (double) – Threshold for testing if probabilities are equal to 0 or 1 (Default: 1e-8).

Raises

NoiseError – If input noise_ops are not a CPTP map.

Methods

__init__(noise_ops[, number_of_qubits, …])	Create a quantum error for a noise model.
compose(other[, front])	Return the composition error channel other * self.
copy()	Make a copy of current QuantumError.
dot(other)	Return the composition error channel self * other.
error_term(position)	Return a single term from the error.
expand(other)	Return the tensor product quantum error channel self ⊗ other.
ideal()	Return True if current error object is an identity
power(n)	Return the compose of a error channel with itself n times.
set_atol(value)	Set the class default absolute tolerance parameter for float comparisons.
set_rtol(value)	Set the class default relative tolerance parameter for float comparisons.
tensor(other)	Return the tensor product quantum error channel self ⊗ other.
to_dict()	Return the current error as a dictionary.
to_instruction()	Convert the QuantumError to a circuit Instruction.
to_quantumchannel()	Convert the QuantumError to a SuperOp quantum channel.

Attributes

atol	The default absolute tolerance parameter for float comparisons.
circuits	Return the list of error circuits.
number_of_qubits	Return the number of qubits for the error.
probabilities	Return the list of error probabilities.
rtol	The relative tolerance parameter for float comparisons.
size	Return the number of error circuit.

property atol

The default absolute tolerance parameter for float comparisons.

property circuits

Return the list of error circuits.

compose(other, front=False)

Return the composition error channel other * self.

Note that for front=True this is equivalent to the QuantumError.dot() method.

Parameters

• other (QuantumError) – a quantum error channel.

• front (bool) – If True return the reverse order composation self * other instead [default: False].

Returns

The composition error channel.

Return type

QuantumError

Raises

• NoiseError – if other cannot be converted into a QuantumError,

• or has incompatible dimensions. –

copy()

Make a copy of current QuantumError.

dot(other)

Return the composition error channel self * other.

Parameters

other (QuantumError) – a quantum error channel.

Returns

The composition error channel.

Return type

QuantumError

Raises

• NoiseError – if other cannot be converted into a QuantumError,

• or has incompatible dimensions. –

error_term(position)

Return a single term from the error.

Parameters

position (int) – the position of the error term.

Returns

A pair (p, circuit) for error term at position < size where p is the probability of the error term, and circuit is the list of qobj instructions for the error term.

Return type

tuple

Raises

• NoiseError – If the position is greater than the size of

• the quantum error. –

expand(other)

Return the tensor product quantum error channel self ⊗ other.

Parameters

other (QuantumError) – a quantum error channel.

Returns

the tensor product error channel other ⊗ self.

Return type

QuantumError

Raises

NoiseError – if other cannot be converted to a QuantumError.

ideal()

Return True if current error object is an identity

property number_of_qubits

Return the number of qubits for the error.

power(n)

Return the compose of a error channel with itself n times.

Parameters

n (int) – the number of times to compose with self (n>0).

Returns

the n-times composition error channel.

Return type

QuantumError

Raises

NoiseError – if the power is not a positive integer.

property probabilities

Return the list of error probabilities.

property rtol

The relative tolerance parameter for float comparisons.

classmethod set_atol(value)

Set the class default absolute tolerance parameter for float comparisons.

classmethod set_rtol(value)

Set the class default relative tolerance parameter for float comparisons.

property size

Return the number of error circuit.

tensor(other)

Return the tensor product quantum error channel self ⊗ other.

Parameters

other (QuantumError) – a quantum error channel.

Returns

the tensor product error channel self ⊗ other.

Return type

QuantumError

Raises

NoiseError – if other cannot be converted to a QuantumError.

to_dict()

Return the current error as a dictionary.

to_instruction()

Convert the QuantumError to a circuit Instruction.

to_quantumchannel()

Convert the QuantumError to a SuperOp quantum channel.