FermionicInstruction

class FermionicInstruction(name, num_qubits, num_clbits, params, label=None)

Bases: Instruction

The base class for all instructions acting on fermionic modes.

This is the type that the fermion-to-qubit synthesis stage dispatches on, so it is what makes an instruction “fermionic” as far as this package is concerned.

Most fermionic instructions are unitary and should subclass FermionicGate instead, which adds the Gate interface on top of this one. Subclass this class directly only for an instruction that cannot be a gate, the motivating case being one that acts on classical bits: Gate fixes its classical-bit count at zero, so a measurement (FermionicMeasure) cannot be a gate.

Caution

Since this is a subclass of Instruction the documentation of its methods may refer to qubits. Those references should be interpreted as referring to fermions in the context of instances of this subclass.

It may also happen that some of the inherited methods may not always make sense because of this re-interpretation. You have been warned.

Deprecated since version 1.3: The parameters duration and unit are deprecated since Qiskit 1.3, and they will be removed in 2.0 or later. An instruction’s duration is defined in a backend’s Target object.

Parameters:

  • name (str) – instruction name

  • num_qubits (int) – instruction’s qubit width

  • num_clbits (int) – instruction’s clbit width

  • params (list[int|float|complex|str|ndarray|list|ParameterExpression]) – list of parameters

  • label (str or None) – An optional label for identifying the instruction.

Raises:

  • CircuitError – when the register is not in the correct format.

  • TypeError – when the optional label is provided, but it is not a string.

Attributes

num_modes

The number of fermionic modes that this instruction acts upon.

Inherited Attributes

base_class

Get the base class of this instruction. This is guaranteed to be in the inheritance tree of self.

The “base class” of an instruction is the lowest class in its inheritance tree that the object should be considered entirely compatible with for _all_ circuit applications. This typically means that the subclass is defined purely to offer some sort of programmer convenience over the base class, and the base class is the “true” class for a behavioral perspective. In particular, you should not override base_class if you are defining a custom version of an instruction that will be implemented differently by hardware, such as an alternative measurement strategy, or a version of a parametrized gate with a particular set of parameters for the purposes of distinguishing it in a Target from the full parametrized gate.

This is often exactly equivalent to type(obj), except in the case of singleton instances of standard-library instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:

>>> isinstance(XGate(), XGate)
True
>>> type(XGate()) is XGate
False
>>> XGate().base_class is XGate
True

In general, you should not rely on the precise class of an instruction; within a given circuit, it is expected that Instruction.name should be a more suitable discriminator in most situations.

decompositions

Get the decompositions of the instruction from the SessionEquivalenceLibrary.

definition

Return definition in terms of other basic gates.

label

Return instruction label

mutable

Is this instance is a mutable unique instance or not.

If this attribute is False the gate instance is a shared singleton and is not mutable.

name

Return the name.

num_clbits

Return the number of clbits.

num_qubits

Return the number of qubits.

params

The parameters of this Instruction. Ideally these will be gate angles.

Inherited Methods

add_decomposition(decomposition)

Add a decomposition of the instruction to the SessionEquivalenceLibrary.

broadcast_arguments(qargs, cargs)

Validation of the arguments.

Parameters:

  • qargs (List) – List of quantum bit arguments.

  • cargs (List) – List of classical bit arguments.

Yields:

Tuple(List, List) – A tuple with single arguments.

Raises:

CircuitError – If the input is not valid. For example, the number of arguments does not match the gate expectation.

copy(name=None)

Copy of the instruction.

Parameters:

name (str) – name to be given to the copied circuit, if None then the name stays the same.

Returns:

a copy of the current instruction, with the name updated if it was provided

Return type:

qiskit.circuit.Instruction

inverse(annotated=False)

Invert this instruction.

If annotated is False, the inverse instruction is implemented as a fresh instruction with the recursively inverted definition.

If annotated is True, the inverse instruction is implemented as AnnotatedOperation, and corresponds to the given instruction annotated with the “inverse modifier”.

Special instructions inheriting from Instruction can implement their own inverse (e.g. T and Tdg, Barrier, etc.) In particular, they can choose how to handle the argument annotated which may include ignoring it and always returning a concrete gate class if the inverse is defined as a standard gate.

Parameters:

annotated (bool) – if set to True the output inverse gate will be returned as AnnotatedOperation.

Returns:

The inverse operation.

Raises:

CircuitError – if the instruction is not composite and an inverse has not been implemented for it.

is_parameterized()

Return whether the Instruction contains compile-time parameters.

repeat(n)

Creates an instruction with self repeated \(n\) times.

Parameters:

n (int) – Number of times to repeat the instruction

Returns:

Containing the definition.

Return type:

qiskit.circuit.Instruction

Raises:

CircuitError – If n < 1.

reverse_ops()

For a composite instruction, reverse the order of sub-instructions.

This is done by recursively reversing all sub-instructions. It does not invert any gate.

Returns:

a new instruction with

sub-instructions reversed.

Return type:

qiskit.circuit.Instruction

soft_compare(other)

Soft comparison between gates. Their names, number of qubits, and classical bit numbers must match. The number of parameters must match. Each parameter is compared. If one is a ParameterExpression then it is not taken into account.

Parameters:

other (instruction) – other instruction.

Returns:

are self and other equal up to parameter expressions.

Return type:

bool

to_mutable()

Return a mutable copy of this gate.

This method will return a new mutable copy of this gate instance. If a singleton instance is being used this will be a new unique instance that can be mutated. If the instance is already mutable it will be a deepcopy of that instance.

validate_parameter(parameter)

Instruction parameter has no validation or normalization.