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T2Fitter

T2Fitter(backend_result, xdata, qubits, fit_p0, fit_bounds, circbasename='t2', time_unit='micro-seconds') GitHub(opens in a new tab)

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)=Aet/T2+B,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,T2,B)(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,T2,B)(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.

Attributes

backend_result

Union[qiskit.result.result.Result, List[qiskit.result.result.Result]]

Return the execution results

Return type

Union[Result, List[Result]]

description

str

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

Return type

str

fit_fun

Callable

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

Return type

Callable

measured_qubits

List[int]

Return the indices of the qubits to be characterized

Return type

List[int]

params

List[float]

Return the fit function parameters that were calculated by curve_fit

Return type

List[float]

params_err

List[float]

Return the error of the fit function parameters

Return type

List[float]

series

Optional[List[str]]

Return the list of series for the data

Return type

Optional[List[str]]

xdata

Union[List[float], numpy.array]

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

Return type

Union[List[float], array]

ydata

List[Dict]

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]


Methods

add_data

T2Fitter.add_data(results, recalc=True, refit=True)

Add new execution results to previous execution results

Parameters

  • results (Union[Result, List[Result]]) – new execution results
  • recalc (bool) – whether tp recalculate the data
  • refit (bool) – whether to refit the data

fit_data

T2Fitter.fit_data(qid=- 1, p0=None, bounds=None, series=None)

Fit the curve.

Compute self._params and self._params_err

Parameters

  • qid (int) – qubit for fitting. If -1 fit for all the qubits
  • p0 (Optional[List[float]]) – initial guess, equivalent to p0 in scipy.optimize
  • bounds (Optional[Tuple[List[float], List[float]]]) – bounds, equivalent to bounds in scipy.optimize
  • series (Optional[str]) – series to fit (if None fit all)

plot

T2Fitter.plot(qind, series='0', ax=None, show_plot=False)

Plot coherence data.

Parameters

  • qind – qubit index to plot
  • series – which series to plot (if list then plot multiple)
  • ax – plot axes
  • show_plot – whether to call plt.show()

Returns

The axes object

Return type

Axes

Raises

ImportError – if matplotlib is not installed

time

T2Fitter.time(qid=- 1, series='0')

Return the characteristic time for the given qubit and series

Parameters

  • qid (int) – the qubit index (or all qubits if -1)
  • series (str) – the series to get

Return type

Union[float, List[float]]

Returns

The characteristic time of the qubit, or all qubits

time_err

T2Fitter.time_err(qid=- 1, series='0')

Return the error of characteristic time for the given qubit and series

Parameters

  • qid (int) – the qubit index (or all qubits if -1)
  • series (str) – the series to get

Return type

Union[float, List[float]]

Returns

The error of the characteristic time of the qubit, or all qubits

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