SaveExpectationValueVariance

class SaveExpectationValueVariance(operator, label='expectation_value_variance', unnormalized=False, pershot=False, conditional=False)

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

Save expectation value and variance of an operator.

Instruction to save the expectation value and variance of a Hermitian operator.

The expectation value of a Hermitian operator \(H\) for a simulator in quantum state :math`rho`is given by \(\langle H\rangle = \mbox{Tr}[H.\rho]\). The variance is given by \(\sigma^2 = \langle H^2 \rangle - \langle H \rangle>^2\).

Parameters

• operator (Pauli or SparsePauliOp or Operator) – 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	Add a decomposition of the instruction to the SessionEquivalenceLibrary.
assemble	Return the QasmQobjInstruction for the intructions.
broadcast_arguments	Validation of the arguments.
c_if	Add classical condition on register or cbit classical and value val.
copy	Copy of the instruction.
inverse	Special case.
is_parameterized	Return True .IFF.
mirror	DEPRECATED: use instruction.reverse_ops().
qasm	Return a default OpenQASM string for the instruction.
repeat	Creates an instruction with gate repeated n amount of times.
reverse_ops	For a composite instruction, reverse the order of sub-instructions.
soft_compare	Soft comparison between gates.
validate_parameter	Instruction parameters has no validation or normalization.

Attributes

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

params

return instruction params.

unit

Get the time unit of duration.