guppyalgos.algorithms.amplitude_amplification.qae

Functions for QAE.

Functions

prepare_and_measure(state_prep, repeat)	Estimate the amplitude by repeated prepare-and-measure sampling.
prepare_and_measure_once(state_prep)	Prepare \(A\ket{0}\) and measure the target qubit once.

guppyalgos.algorithms.amplitude_amplification.qae.prepare_and_measure(state_prep, repeat)

Estimate the amplitude by repeated prepare-and-measure sampling.

Runs prepare_and_measure_once() repeat times and returns the fraction of repetitions in which the target was measured in \(\ket{1}\), i.e. count(1) / repeat. The estimate converges to the amplitude \(a = P(\text{target} = 1)\) with standard error \(\sqrt{a(1-a)/repeat}\).

Parameters:

• state_prep – The state-preparation unitary \(A\); see prepare_and_measure_once().

• repeat – The number of prepare-and-measure repetitions. Must be at least 1.

Returns:

The estimated amplitude in [0, 1].

guppyalgos.algorithms.amplitude_amplification.qae.prepare_and_measure_once(state_prep)

Prepare \(A\ket{0}\) and measure the target qubit once.

Allocates an n-qubit register together with a single target qubit, all in \(\ket{0}\), applies the state-preparation unitary state_prep (\(A\)), and measures the target in the computational basis. The register is discarded.

Parameters:

state_prep – The state-preparation unitary \(A\), acting on the register (assumed to start in \(\ket{0}\)) and the target qubit. It must flag the “good” subspace on the target qubit, i.e. arrange that measuring the target yields \(\ket{1}\) with probability equal to the amplitude.

Returns:

The measured target outcome, True for \(\ket{1}\) and False for \(\ket{0}\).