Note

This is the documentation for the current state of the development branch of Qiskit Experiments. The documentation or APIs here can change prior to being released.

Tphi

class Tphi(physical_qubits, delays_t1, delays_t2, t2type='hahn', osc_freq=0.0, num_echoes=1, backend=None)

An experiment to measure the qubit dephasing rate in the \(x - y\) plane.

Overview

\(T_\varphi\), or \(1/\Gamma_\varphi\), is the pure dephasing time in the \(x - y\) plane of the Bloch sphere. We compute \(\Gamma_\varphi\) by computing \(\Gamma_2\), the transverse relaxation rate, and subtracting \(\Gamma_1\), the longitudinal relaxation rate. It follows that

\(1/T_\varphi = 1/T_2 - 1/2T_1\).

The transverse relaxation rate can be estimated by either \(T_2\) or \(T_2^*\) experiments. In superconducting qubits, \(T_2^*\) tends to be significantly smaller than \(T_1\), so \(T_2\) is usually used.

Note

In 0.5.0, this experiment changed from using \(T_2^*\) as the default to \(T_2\).

References

[1] Philip Krantz, Morten Kjaergaard, Fei Yan, Terry P. Orlando, Simon Gustavsson, William D. Oliver, A Quantum Engineer’s Guide to Superconducting Qubits, Applied Physics Reviews 6, 021318 (2019), doi: 10.1063/1.5089550 (open)

User manual

Tφ Characterization

Analysis class reference

TPhiAnalysis

Experiment options

These options can be set by the set_experiment_options() method.

Options

• Defined in the class BatchExperiment:

  • separate_jobs (Boolean)

    Default value: False

    Whether to route different sub-experiments to different jobs.

• Defined in the class BaseExperiment:

  • max_circuits (Optional[int])

    Default value: None

    The maximum number of circuits per job when running an experiment on a backend.

See also

• qiskit_experiments.library.characterization.T1

• qiskit_experiments.library.characterization.T2Ramsey

• qiskit_experiments.library.characterization.T2Hahn

Initialization

Initialize the experiment object.

Parameters:

• physical_qubits (Sequence[int]) – A single-element sequence containing the qubit under test.

• t2type (str) – What type of T2/T2* experiment to use. Can be either “ramsey” for T2Ramsey to be used, or “hahn” for T2Hahn. Defaults to “hahn”.

• delays_t1 (List[Union[List[float], array]]) – Delay times of the T1 experiment.

• delays_t2 (List[Union[List[float], array]]) – Delay times of the T2 experiment.

• osc_freq (float) – The oscillation frequency induced for T2Ramsey. Only used when t2type is set to “ramsey”.

• num_echoes (int) – The number of echoes to perform for T2Hahn. Only used when t2type is set to “hahn”.

• backend (Optional[Backend]) – Optional, the backend on which to run the experiment.

Raises:

QiskitError – If an invalid t2type is provided.

Attributes

Tphi.analysis	Return the analysis instance for the experiment
Tphi.backend	Return the backend for the experiment
Tphi.experiment_options	Return the options for the experiment.
Tphi.experiment_type	Return experiment type.
Tphi.num_experiments	Return the number of sub experiments
Tphi.num_qubits	Return the number of qubits for the experiment.
Tphi.physical_qubits	Return the device qubits for the experiment.
Tphi.run_options	Return options values for the experiment run() method.
Tphi.transpile_options	Return the transpiler options for the run() method.

Methods

Tphi.circuits()	Return a list of experiment circuits.
Tphi.component_experiment([index])	Return the component Experiment object.
Tphi.config()	Return the config dataclass for this experiment
Tphi.copy()	Return a copy of the experiment
Tphi.from_config(config)	Initialize an experiment from experiment config
Tphi.run([backend, analysis, timeout])	Run an experiment and perform analysis.
Tphi.set_experiment_options(**fields)	Set the experiment options.
Tphi.set_run_options(**fields)	Set options values for the experiment run() method.
Tphi.set_transpile_options(**fields)	Set the transpiler options for run() method.