T2Ramsey#

class T2Ramsey(physical_qubits, delays, backend=None, osc_freq=0.0)[source]#

An experiment to measure the Ramsey frequency and the qubit dephasing time sensitive to inhomogeneous broadening.

Overview

This experiment is used to estimate two properties for a single qubit: \(T_2^*\) and Ramsey frequency. \(T_2^*\) is the dephasing time or the transverse relaxation time of the qubit on the Bloch sphere as a result of both energy relaxation and pure dephasing in the transverse plane. Unlike \(T_2\), which is measured by T2Hahn, \(T_2^*\) is sensitive to inhomogenous broadening.

This experiment consists of a series of circuits of the form

     ┌───┐┌──────────────┐┌──────┐ ░ ┌───┐ ░ ┌─┐
q_0: ┤ H ├┤   DELAY(t)   ├┤ P(λ) ├─░─┤ H ├─░─┤M├
     └───┘└──────────────┘└──────┘ ░ └───┘ ░ └╥┘
c: 1/═════════════════════════════════════════╩═
                                            0

for each t from the specified delay times, where \(\lambda =2 \pi \times {osc\_freq}\), and the delays are specified by the user. The circuits are run on the device or on a simulator backend.

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

T2* Ramsey Characterization

Analysis class reference

T2RamseyAnalysis

Experiment options

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

Options

Defined in the class T2Ramsey:
- delays (Iterable[float])
  
  Default value: None
  
  Delay times of the experiments in seconds.
- osc_freq (float)
  
  Default value: 0.0
  
  Oscillation frequency offset in Hz.
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.

Initialization

Initialize the T2Ramsey class.

Parameters:

physical_qubits (Sequence[int]) – a single-element sequence containing the qubit under test.
delays (List[float] | array) – delay times of the experiments in seconds.
backend (Backend | None) – Optional, the backend to run the experiment on.
osc_freq (float) – the oscillation frequency induced by the user. The frequency is given in Hz.

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_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()[source]#

Return a list of experiment circuits.

Each circuit consists of a Hadamard gate, followed by a fixed delay, a phase gate (with a linear phase), and an additional Hadamard gate.

Returns:: The experiment circuits
Return type:: List[QuantumCircuit]

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)#

Set the experiment options.

Parameters:: fields – The fields to update the options
Raises:: AttributeError – If the field passed in is not a supported options

set_run_options(**fields)#

Set options values for the experiment run() method.

Parameters:: fields – The fields to update the options