T2Fitter¶

class T2Fitter(backend_result, xdata, qubits, fit_p0, fit_bounds, circbasename='t2', time_unit='micro-seconds')[source]¶

Bases: qiskit.ignis.characterization.fitters.BaseCoherenceFitter

Estimate T₂, based on experiments outcomes.

The experiments were created by t2_circuits, and executed on the device.

The probabilities of measuring 0 is assumed to be of the form

\[f(t) = A\mathrm{e}^{-t/T_2}+B,\]

for unknown parameters A, B, and T₂.

Parameters

backend_result (Result) – result of execution of t2_circuits on the backend.
xdata (Union[List[float], array]) – delay times of the T₂ circuits.
qubits (List[int]) – indices of the qubits whose T₂‘s are to be measured.
fit_p0 (List[float]) – initial values to the fit parameters, where the order is \((A, T_2, B)\).
fit_bounds (Tuple[List[float], List[float]]) – bounds on the parameters to fit. The first tuple is the lower bounds, in the order \((A, T_2, B)\). The second tuple is the upper bounds.
circbasename (str) – prefix to all circuit names.
time_unit (str) – unit of delay times in xdata.

Methods

`add_data`	Add new execution results to previous execution results
`fit_data`	Fit the curve.
`plot`	Plot coherence data.
`time`	Return the characteristic time for the given qubit and series
`time_err`	Return the error of characteristic time for the given qubit and series

Attributes

backend_result¶

Return the execution results

Return type: Union[Result, List[Result]]

description¶

Return the fitter’s purpose, e.g. ‘T1’

Return type: str

fit_fun¶

Return the function used in the fit, e.g. BaseFitter._exp_fit_fun

Return type: Callable

measured_qubits¶

Return the indices of the qubits to be characterized

Return type: List[int]

params¶

Return the fit function parameters that were calculated by curve_fit

Return type: List[float]

params_err¶

Return the error of the fit function parameters

Return type: List[float]

series¶

Return the list of series for the data

Return type: Optional[List[str]]

xdata¶

Return the data points on the x-axis, the independenet parameter which is fit against

Return type: Union[List[float], array]

ydata¶

Return the data points on the y-axis

The data points are returning in the form of a list of dictionaries:

ydata[i][‘mean’] is a list, where item
no. j is the probability of success of qubit i for a circuit that lasts xdata[j].

ydata[i][‘std’] is a list, where ydata[‘std’][j] is the
standard deviation of the success of qubit i.

Return type: List[Dict]