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SaveExpectationValue

SaveExpectationValue(operator, label='expectation_value', unnormalized=False, pershot=False, conditional=False)

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Bases: qiskit.providers.aer.library.save_instructions.save_data.SaveAverageData

Save expectation value of an operator.

Instruction to save the expectation value of a Hermitian operator.

The expectation value of a Hermitian operator HH for a simulator in quantum state :math`rho`is given by H=Tr[H.ρ]\langle H\rangle = \text{Tr}[H.\rho].

Parameters

  • operator (Pauli orSparsePauliOp orOperator) – a Hermitian operator.
  • label (str) – the key for retrieving saved data from results.
  • unnormalized (bool) – If True return save the unnormalized accumulated or conditional accumulated expectation value over all shot [Default: False].
  • pershot (bool) – if True save a list of expectation values for each shot of the simulation rather than the average over all shots [Default: False].
  • conditional (bool) – if True save the average or pershot data conditional on the current classical register values [Default: False].

Raises

ExtensionError – if the input operator is invalid or not Hermitian.

Note

This instruction can be directly appended to a circuit using the save_expectation_value() circuit method.


Methods

add_decomposition

SaveExpectationValue.add_decomposition(decomposition)

Add a decomposition of the instruction to the SessionEquivalenceLibrary.

assemble

SaveExpectationValue.assemble()

Return the QasmQobjInstruction for the intructions.

broadcast_arguments

SaveExpectationValue.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.

c_if

SaveExpectationValue.c_if(classical, val)

Set a classical equality condition on this instruction between the register or cbit classical and value val.

Note

This is a setter method, not an additive one. Calling this multiple times will silently override any previously set condition; it does not stack.

copy

SaveExpectationValue.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

SaveExpectationValue.inverse()

Special case. Return self.

is_parameterized

SaveExpectationValue.is_parameterized()

Return True .IFF. instruction is parameterized else False

qasm

SaveExpectationValue.qasm()

Return a default OpenQASM string for the instruction.

Derived instructions may override this to print in a different format (e.g. measure q[0] -> c[0];).

repeat

SaveExpectationValue.repeat(n)

Creates an instruction with gate repeated n amount of 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

SaveExpectationValue.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

SaveExpectationValue.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

validate_parameter

SaveExpectationValue.validate_parameter(parameter)

Instruction parameters has no validation or normalization.


Attributes

condition_bits

Get Clbits in condition.

Return type

List[Clbit]

decompositions

Get the decompositions of the instruction from the SessionEquivalenceLibrary.

definition

Return definition in terms of other basic gates.

duration

Get the duration.

label

Return instruction label

Return type

str

name

Return the name.

num_clbits

Return the number of clbits.

num_qubits

Return the number of qubits.

params

return instruction params.

unit

Get the time unit of duration.

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