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.

RoughDrag

class RoughDrag(physical_qubits, schedule, betas=None, backend=None)

An experiment that scans the DRAG parameter to find the optimal value.

Overview

A Derivative Removal by Adiabatic Gate (DRAG) pulse is designed to minimize phase errors and leakage resulting from the presence of a neighbouring transition. DRAG is a standard pulse with an additional derivative component. The optimal value of the DRAG parameter, $\beta$, is chosen to primarily minimize phase errors resulting from the AC Stark shift and potentially leakage errors. The DRAG pulse is

$$f(t)=\mathrm{\Omega }(t)+1j\beta d/dt\mathrm{\Omega }(t)$$

Here, $\mathrm{\Omega }$ is the envelop of the in-phase component of the pulse and $\beta$ is the strength of the quadrature which we refer to as the DRAG parameter and seek to calibrate in this experiment. The DRAG calibration will run several series of circuits. In a given circuit a Rp(β) - Rm(β) block is repeated $N$ times. Here, Rp is a rotation with a positive angle and Rm is the same rotation with a native angle and is implemented by the gate sequence Rz(π) - Rp(β) - Rz(π) where the Z rotations are virtual. As example the circuit of a single repetition, i.e. $N=1$, is shown below.

           ┌───────┐┌───────┐┌───────┐┌───────┐ ░ ┌─┐
      q_0: ┤ Rp(β) ├┤ Rz(π) ├┤ Rp(β) ├┤ Rz(π) ├─░─┤M├
           └───────┘└───────┘└───────┘└───────┘ ░ └╥┘
measure: 1/════════════════════════════════════════╩═
                                                   0

The parameter β is scanned to find the value that minimizes the unwanted Z-rotation. Note that the analysis class requires this experiment to run with three repetition numbers.

References

[1] J. M. Gambetta, F. Motzoi, S. T. Merkel, F. K. Wilhelm, Analytic control methods for high fidelity unitary operations in a weakly nonlinear oscillator, Phys. Rev. A 83, 012308 (2011), doi: 10.1103/PhysRevA.83.012308 (open)

[2] F. Motzoi, J. M. Gambetta, P. Rebentrost, F. K. Wilhelm, Simple pulses for elimination of leakage in weakly nonlinear qubits, Phys. Rev. Lett. 103, 110501 (2009), doi: 10.1103/PhysRevLett.103.110501 (open)

[3] Zijun Chen, Julian Kelly, Chris Quintana, R. Barends, B. Campbell, Yu Chen, B. Chiaro, A. Dunsworth, A. Fowler, E. Lucero, E. Jeffrey, A. Megrant, J. Mutus, M. Neeley, C. Neill, P. J. J. O’Malley, P. Roushan, D. Sank, A. Vainsencher, J. Wenner, T. C. White, A. N. Korotkov, John M. Martinis, Measuring and Suppressing Quantum State Leakage in a Superconducting Qubit, Phys. Rev. Lett. 116, 020501 (2016), doi: 10.1103/PhysRevLett.116.020501 (open)

User manual

Calibrating the value of the DRAG coefficient

Analysis class reference

DragCalAnalysis

Experiment options

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

Options

• Defined in the class RoughDrag:

  • schedule (ScheduleBlock)

    Default value: None

    The schedule of the rotation.

  • reps (List[int])

    Default value: [1, 3, 5]

    The number of times the Rp - Rm gate sequence is repeated in each series. Note that this list must always have a length of three as otherwise the analysis class will not run.

  • betas (Iterable)

    Default value: array(-5.0, -4.8, -4.6, -4.4, -4.2, ..., size=51)

    the values of the DRAG parameter to scan.

• 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 a Drag experiment in the given qubit.

Parameters:

• physical_qubits (Sequence[int]) – Sequence containing the qubit for which to run the Drag calibration.

• schedule (ScheduleBlock) – The schedule to run. This schedule should have one free parameter corresponding to a DRAG parameter.

• betas (Optional[Iterable[float]]) – The values of the DRAG parameter to scan. If None is given the default range linspace(-5, 5, 51) is used.

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

Raises:

QiskitError – If the schedule does not have a free parameter.

Attributes

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

Methods

RoughDrag.circuits()	Create the circuits for the Drag calibration.
RoughDrag.config()	Return the config dataclass for this experiment
RoughDrag.copy()	Return a copy of the experiment
RoughDrag.enable_restless([rep_delay, ...])	Enables a restless experiment by setting the restless run options and the restless data processor.
RoughDrag.from_config(config)	Initialize an experiment from experiment config
RoughDrag.run([backend, analysis, timeout])	Run an experiment and perform analysis.
RoughDrag.set_experiment_options(**fields)	Set the experiment options.
RoughDrag.set_run_options(**fields)	Set options values for the experiment run() method.
RoughDrag.set_transpile_options(**fields)	Set the transpiler options for run() method.