Randomized Benchmarking

RandomizedBenchmarkingModel - Likelihood for RB experiments

Class Reference

class qinfer.RandomizedBenchmarkingModel(interleaved=False, order=0)

Bases: qinfer.abstract_model.FiniteOutcomeModel, qinfer.abstract_model.DifferentiableModel

Implements the randomized benchmarking or interleaved randomized benchmarking protocol, such that the depolarizing strength \(p\) of the twirled channel is a parameter to be estimated, given a sequnce length \(m\) as an experimental control. In addition, the zeroth-order “fitting”-parameters \(A\) and \(B\) are represented as model parameters to be estimated.

Parameters:

interleaved (bool) – If True, the model implements the interleaved protocol, with \(\tilde{p}\) being the depolarizing parameter for the interleaved gate and with \(p_{\text{ref}}\) being the reference parameter.

Model Parameters:  

• p – Fidelity of the twirled error channel \(\Lambda\), represented as a decay rate \(p = (d F - 1) / (d - 1)\), where \(F\) is the fidelity and \(d\) is the dimension of the Hilbert space.
• A – Scale of the randomized benchmarking decay, defined as \(\Tr[Q \Lambda(\rho - \ident / d)]\), where \(Q\) is the final measurement, and where \(\ident\) is the initial preparation.
• B – Offset of the randomized benchmarking decay, defined as \(\Tr[Q \Lambda(\ident / d)]\).

Experiment Parameters:  

• m (int) – Length of the randomized benchmarking sequence that was measured.

n_modelparams

modelparam_names

is_n_outcomes_constant

expparams_dtype

n_outcomes(expparams)

are_models_valid(modelparams)

likelihood(outcomes, modelparams, expparams)

score(outcomes, modelparams, expparams, return_L=False)

Function Reference

qinfer.rb.p(F, d=2)

Given the fidelity of a gate in \(d\) dimensions, returns the depolarizating probability of the twirled channel.

Parameters:

• F (float) – Fidelity of a gate.
• d (int) – Dimensionality of the Hilbert space on which the gate acts.

qinfer.rb.F(p, d=2)

Given the depolarizating probabilty of a twirled channel in \(d\) dimensions, returns the fidelity of the original gate.

Parameters:

• p (float) – Depolarizing parameter for the twirled channel.
• d (int) – Dimensionality of the Hilbert space on which the gate acts.