Amplitude estimation

amplitude_estimation

amplitude_estimation(
    oracle: QCallable[QArray[QBit]],
    space_transform: QCallable[QArray[QBit]],
    phase: QNum,
    packed_vars: QArray[QBit],
) -> None

[Qmod Classiq-library function]

Estimate the probability of a state being marked by the operand oracle as a "good state."

The algorithm prepares the state in the packed_vars register and estimates the probability of this state being marked by the oracle as a "good state." This is done using the Quantum Phase Estimation (QPE) algorithm, where the unitary for QPE is the Grover operator, which is composed of the oracle and space_transform operators.

Parameters:

Name	Type	Description	Default
oracle	QCallable[QArray[QBit]]	The oracle operator that marks the "good" state. This operator should flip the sign of the amplitude of the "good" state.	required
space_transform	QCallable[QArray[QBit]]	The space transform operator (which is known also the state preparation operator), which is first applied to prepare the state before the QPE, and then used inside the Grover operator.	required
phase	QNum	Assuming this variable starts from the zero state -this variable output holds the \(phase=\theta\) result in the [0,1] domain, which relates to the estimated probability \(a\) through \(a=\sin^2(\pi \theta)\).	required
packed_vars	QArray[QBit]	The variable that holds the state to be estimated. Assumed to be in the zero state at the beginning of the algorithm.	required