339 lines
11 KiB
Plaintext
339 lines
11 KiB
Plaintext
---
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title: QuantumError
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description: API reference for qiskit_aer.noise.QuantumError
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit_aer.noise.QuantumError
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---
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# QuantumError
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<Class id="qiskit_aer.noise.QuantumError" isDedicatedPage={true} github="https://github.com/qiskit/qiskit-aer/tree/stable/0.11/qiskit_aer/noise/errors/quantum_error.py" signature="QuantumError(noise_ops, number_of_qubits=None, standard_gates=None, atol=None)" modifiers="class">
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Bases: `qiskit.quantum_info.operators.base_operator.BaseOperator`, `qiskit.quantum_info.operators.mixins.tolerances.TolerancesMixin`
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Quantum error class for Qiskit Aer noise model
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<Admonition title="Warning" type="caution">
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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.
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</Admonition>
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Create a quantum error for a noise model.
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Noise ops may either be specified as a `QuantumChannel` for a general CPTP map, or as a list of `(circuit, p)` pairs where `circuit` is a circuit-like object for the noise, and `p` is the probability of the noise event. Any type of input will be converted to the probabilistic mixture of circuit format.
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**Example**
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An example noise\_ops for a bit-flip error with error probability `p = 0.1` is:
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```python
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noise_ops = [(IGate(), 0.9),
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(XGate(), 0.1)]
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```
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or specifying explicit qubit arguments,
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```python
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noise_ops = [((IGate(), [0]), 0.9),
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((XGate(), [0]), 0.1)]
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```
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The same error represented as a Kraus channel can be input as:
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```python
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noise_ops = Kraus([np.sqrt(0.9) * np.array([[1, 0], [0, 1]]),
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np.sqrt(0.1) * np.array([[0, 1], [1, 0]])])
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```
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**Parameters**
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* **noise\_ops** (*QuantumChannel or Iterable*) – Either a quantum channel or a list of `(circuit, p)` pairs, which represents a quantum error, where `circuit` is a circuit-like object for the noise, and `p` is the probability of the noise event. Circuit-like types include `QuantumCircuit`, `(Instruction, qargs)` and a list of `(Instruction, qargs)`. Note that `qargs` should be a list of integers and can be omitted (default qubits are used in that case). See also examples above.
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* **number\_of\_qubits** (*int*) – \[DEPRECATED] specify the number of qubits for the error. If None this will be determined automatically (default None).
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* **standard\_gates** (*bool*) – \[DEPRECATED] Check if input matrices are standard gates.
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* **atol** (*double*) – \[DEPRECATED] Threshold for testing if probabilities are equal to 0 or 1 (Default: `QuantumError.atol`).
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**Raises**
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**NoiseError** – If input noise\_ops is invalid, e.g. it’s not a CPTP map.
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## Methods
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### compose
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<Function id="qiskit_aer.noise.QuantumError.compose" signature="QuantumError.compose(other, qargs=None, front=False)">
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Return the operator composition with another CLASS.
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**Parameters**
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* **other** (*CLASS*) – a CLASS object.
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* **qargs** (*list or None*) – Optional, a list of subsystem positions to apply other on. If None apply on all subsystems (default: None).
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* **front** (*bool*) – If True compose using right operator multiplication, instead of left multiplication \[default: False].
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**Returns**
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The composed CLASS.
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**Return type**
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CLASS
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**Raises**
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**QiskitError** – if other cannot be converted to an operator, or has incompatible dimensions for specified subsystems.
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<Admonition title="Note" type="note">
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Composition (`&`) by default is defined as left matrix multiplication for matrix operators, while `@` (equivalent to [`dot()`](qiskit_aer.noise.QuantumError#dot "qiskit_aer.noise.QuantumError.dot")) is defined as right matrix multiplication. That is that `A & B == A.compose(B)` is equivalent to `B @ A == B.dot(A)` when `A` and `B` are of the same type.
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Setting the `front=True` kwarg changes this to right matrix multiplication and is equivalent to the [`dot()`](qiskit_aer.noise.QuantumError#dot "qiskit_aer.noise.QuantumError.dot") method `A.dot(B) == A.compose(B, front=True)`.
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</Admonition>
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</Function>
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### copy
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<Function id="qiskit_aer.noise.QuantumError.copy" signature="QuantumError.copy()">
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Make a copy of current QuantumError.
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</Function>
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### dot
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<Function id="qiskit_aer.noise.QuantumError.dot" signature="QuantumError.dot(other, qargs=None)">
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Return the right multiplied operator self \* other.
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**Parameters**
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* **other** ([*Operator*](qiskit.quantum_info.Operator "qiskit.quantum_info.Operator")) – an operator object.
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* **qargs** (*list or None*) – Optional, a list of subsystem positions to apply other on. If None apply on all subsystems (default: None).
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**Returns**
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The right matrix multiplied Operator.
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**Return type**
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[Operator](qiskit.quantum_info.Operator "qiskit.quantum_info.Operator")
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<Admonition title="Note" type="note">
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The dot product can be obtained using the `@` binary operator. Hence `a.dot(b)` is equivalent to `a @ b`.
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</Admonition>
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</Function>
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### error\_term
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<Function id="qiskit_aer.noise.QuantumError.error_term" signature="QuantumError.error_term(position)">
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Return a single term from the error.
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**Parameters**
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**position** (*int*) – the position of the error term.
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**Returns**
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A pair (circuit, p) 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.
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**Return type**
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tuple
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**Raises**
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* **NoiseError** – If the position is greater than the size of
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* **the quantum error.** –
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</Function>
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### expand
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<Function id="qiskit_aer.noise.QuantumError.expand" signature="QuantumError.expand(other)">
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Return the reverse-order tensor product with another CLASS.
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**Parameters**
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**other** (*CLASS*) – a CLASS object.
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**Returns**
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**the tensor product $b \otimes a$, where $a$**
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is the current CLASS, and $b$ is the other CLASS.
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**Return type**
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CLASS
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</Function>
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### ideal
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<Function id="qiskit_aer.noise.QuantumError.ideal" signature="QuantumError.ideal()">
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Return True if this error object is composed only of identity operations. Note that the identity check is best effort and up to global phase.
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</Function>
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### input\_dims
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<Function id="qiskit_aer.noise.QuantumError.input_dims" signature="QuantumError.input_dims(qargs=None)">
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Return tuple of input dimension for specified subsystems.
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</Function>
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### output\_dims
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<Function id="qiskit_aer.noise.QuantumError.output_dims" signature="QuantumError.output_dims(qargs=None)">
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Return tuple of output dimension for specified subsystems.
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</Function>
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### power
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<Function id="qiskit_aer.noise.QuantumError.power" signature="QuantumError.power(n)">
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Return the compose of a operator with itself n times.
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**Parameters**
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**n** (*int*) – the number of times to compose with self (n>0).
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**Returns**
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the n-times composed operator.
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**Return type**
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[Pauli](qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli")
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**Raises**
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**QiskitError** – if the input and output dimensions of the operator are not equal, or the power is not a positive integer.
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</Function>
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### reshape
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<Function id="qiskit_aer.noise.QuantumError.reshape" signature="QuantumError.reshape(input_dims=None, output_dims=None, num_qubits=None)">
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Return a shallow copy with reshaped input and output subsystem dimensions.
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**Parameters**
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* **input\_dims** (*None or tuple*) – new subsystem input dimensions. If None the original input dims will be preserved \[Default: None].
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* **output\_dims** (*None or tuple*) – new subsystem output dimensions. If None the original output dims will be preserved \[Default: None].
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* **num\_qubits** (*None or int*) – reshape to an N-qubit operator \[Default: None].
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**Returns**
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returns self with reshaped input and output dimensions.
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**Return type**
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BaseOperator
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**Raises**
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**QiskitError** – if combined size of all subsystem input dimension or subsystem output dimensions is not constant.
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</Function>
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### set\_atol
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<Function id="qiskit_aer.noise.QuantumError.set_atol" signature="QuantumError.set_atol(value)" modifiers="classmethod">
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Set the class default absolute tolerance parameter for float comparisons.
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</Function>
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### set\_rtol
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<Function id="qiskit_aer.noise.QuantumError.set_rtol" signature="QuantumError.set_rtol(value)" modifiers="classmethod">
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Set the class default relative tolerance parameter for float comparisons.
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</Function>
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### tensor
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<Function id="qiskit_aer.noise.QuantumError.tensor" signature="QuantumError.tensor(other)">
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Return the tensor product with another CLASS.
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**Parameters**
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**other** (*CLASS*) – a CLASS object.
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**Returns**
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**the tensor product $a \otimes b$, where $a$**
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is the current CLASS, and $b$ is the other CLASS.
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**Return type**
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CLASS
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<Admonition title="Note" type="note">
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The tensor product can be obtained using the `^` binary operator. Hence `a.tensor(b)` is equivalent to `a ^ b`.
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</Admonition>
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</Function>
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### to\_dict
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<Function id="qiskit_aer.noise.QuantumError.to_dict" signature="QuantumError.to_dict()">
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Return the current error as a dictionary.
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</Function>
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### to\_instruction
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<Function id="qiskit_aer.noise.QuantumError.to_instruction" signature="QuantumError.to_instruction()">
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Convert the QuantumError to a circuit Instruction.
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</Function>
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### to\_quantumchannel
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<Function id="qiskit_aer.noise.QuantumError.to_quantumchannel" signature="QuantumError.to_quantumchannel()">
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Convert the QuantumError to a SuperOp quantum channel. Required to enable SuperOp(QuantumError).
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</Function>
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## Attributes
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### atol
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<Attribute id="qiskit_aer.noise.QuantumError.atol" attributeValue="1e-08" />
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### circuits
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<Attribute id="qiskit_aer.noise.QuantumError.circuits">
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Return the list of error circuits.
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</Attribute>
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### dim
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<Attribute id="qiskit_aer.noise.QuantumError.dim">
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Return tuple (input\_shape, output\_shape).
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</Attribute>
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### id
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<Attribute id="qiskit_aer.noise.QuantumError.id">
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Return unique ID string for error
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</Attribute>
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### num\_qubits
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<Attribute id="qiskit_aer.noise.QuantumError.num_qubits">
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Return the number of qubits if a N-qubit operator or None otherwise.
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</Attribute>
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### number\_of\_qubits
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<Attribute id="qiskit_aer.noise.QuantumError.number_of_qubits">
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Return the number of qubits for the error.
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</Attribute>
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### probabilities
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<Attribute id="qiskit_aer.noise.QuantumError.probabilities">
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Return the list of error probabilities.
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</Attribute>
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### qargs
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<Attribute id="qiskit_aer.noise.QuantumError.qargs">
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Return the qargs for the operator.
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</Attribute>
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### rtol
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<Attribute id="qiskit_aer.noise.QuantumError.rtol" attributeValue="1e-05" />
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### size
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<Attribute id="qiskit_aer.noise.QuantumError.size">
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Return the number of error circuit.
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</Attribute>
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</Class>
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