Tphi#

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

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

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[List[float] | array]) – Delay times of the T1 experiment.
delays_t2 (List[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 (Backend | None) – Optional, the backend on which to run the experiment.

Raises:

QiskitError – If an invalid t2type is provided.

Attributes

analysis#: Return the analysis instance for the experiment

backend#: Return the backend for the experiment

experiment_options#: Return the options for the experiment.

experiment_type#: Return experiment type.

num_experiments#: Return the number of sub experiments

num_qubits#: Return the number of qubits for the experiment.

physical_qubits#: Return the device qubits for the experiment.

run_options#: Return options values for the experiment run() method.

transpile_options#: Return the transpiler options for the run() method.

Methods

circuits()#

Return a list of experiment circuits.

Returns:: A list of QuantumCircuit.

Note

These circuits should be on qubits [0, .., N-1] for an N-qubit experiment. The circuits mapped to physical qubits are obtained via the internal _transpiled_circuits() method.

component_experiment(index=None)#

Return the component Experiment object.

Parameters:: index (int) – Experiment index, or None if all experiments are to be returned.
Returns:: The component experiment(s).
Return type:: BaseExperiment

config()#

Return the config dataclass for this experiment

Return type:: ExperimentConfig

copy()#

Return a copy of the experiment

Return type:: BaseExperiment

classmethod from_config(config)#

Initialize an experiment from experiment config

Return type:: BaseExperiment

job_info(backend=None)#

Get information about job distribution for the experiment on a specific backend.

Parameters:

backend (Backend) – Optional, the backend for which to get job distribution information. If not specified, the experiment must already have a set backend.

Returns:

A dictionary containing information about job distribution.

”Total number of circuits in the experiment”: Total number of circuits in the experiment.

”Maximum number of circuits per job”: Maximum number of circuits in one job based on backend and experiment settings.

”Total number of jobs”: Number of jobs needed to run this experiment on the currently set backend.

Return type:

dict

Raises:

QiskitError – if backend is not specified.

run(backend=None, analysis='default', timeout=None, **run_options)#

Run an experiment and perform analysis.

Parameters:

backend (Backend | None) – Optional, the backend to run the experiment on. This will override any currently set backends for the single execution.
analysis (BaseAnalysis | None) – Optional, a custom analysis instance to use for performing analysis. If None analysis will not be run. If "default" the experiments analysis() instance will be used if it contains one.
timeout (float | None) – Time to wait for experiment jobs to finish running before cancelling.
run_options – backend runtime options used for circuit execution.

Returns:

The experiment data object.

Raises:

QiskitError – If experiment is run with an incompatible existing ExperimentData container.

Return type:

ExperimentData

set_experiment_options(**fields)[source]#

Set the experiment options. :param fields: The fields defining the options.

Raises:: QiskitError – Invalid input option.

set_run_options(**fields)#

Set options values for the experiment run() method.

Parameters:: fields – The fields to update the options