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.

EchoedCrossResonanceHamiltonian

class EchoedCrossResonanceHamiltonian(physical_qubits, flat_top_widths=None, backend=None, cr_gate=None, durations=None, **kwargs)

Echoed cross resonance Hamiltonian tomography experiment.

Overview

This is a variant of CrossResonanceHamiltonian for which the experiment framework is identical but the cross resonance operation is realized as an echoed sequence to remove unwanted single qubit rotations. The cross resonance circuit looks like:

     ┌────────────────────┐  ┌───┐  ┌────────────────────┐
q_0: ┤0                   ├──┤ X ├──┤0                   ├──────────
     │  cr_tone(duration) │┌─┴───┴─┐│  cr_tone(duration) │┌────────┐
q_1: ┤1                   ├┤ Rz(π) ├┤1                   ├┤ Rz(-π) ├
     └────────────────────┘└───────┘└────────────────────┘└────────┘

Here two cr_tone are applied, where the latter one is with the control qubit state flipped and with a phase flip of the target qubit frame. This operation is equivalent to applying the cr_tone with a negative amplitude. The Hamiltonian for this decomposition has no IX and ZI interactions, and also a reduced IY interaction to some extent (not completely eliminated) [1]. Note that the CR Hamiltonian tomography experiment cannot detect the ZI term. However, it is sensitive to the IX and IY terms.

References

[1] Neereja Sundaresan, Isaac Lauer, Emily Pritchett, Easwar Magesan, Petar Jurcevic, Jay M. Gambetta, Reducing unitary and spectator errors in cross resonance with optimized rotary echoes, PRX Quantum 1, 020318 (2020), doi: 10.1103/PRXQuantum.1.020318 (open)

Analysis class reference

CrossResonanceHamiltonianAnalysis

Experiment options

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

Options

• Defined in the class CrossResonanceHamiltonian:

  • flat_top_widths (np.ndarray)

    Default value: None

    Deprecated. Length of Gaussian flat top to scan.

  • durations (np.ndarray)

    Default value: None

    The total duration of the cross resonance pulse(s) to scan, in units of sec. Values should be longer than pulse ramps.

  • min_durations (int)

    Default value: 6e-08

    The minimum default pulse duration in samples.

  • max_durations (int)

    Default value: 1.2e-06

    The maximum default pulse duration in samples.

  • num_durations (int)

    Default value: 48

    The number of measured durations. The experiment automatically creates durations of linear increment along with min_durations and max_durations when user doesn’t explicitly provide durations.

  • amp (complex)

    Default value: 0.5

    Amplitude of the cross resonance tone.

  • amp_t (complex)

    Default value: 0.0

    Amplitude of the cancellation or rotary drive on target qubit.

  • sigma (float)

    Default value: 64

    Sigma of Gaussian rise and fall edges, in units of dt.

  • risefall (float)

    Default value: 2

    Ratio of edge durations to sigma.

• 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

• Superclass qiskit_experiments.library.characterization.cr_hamiltonian.CrossResonanceHamiltonian

Initialization

Create a new experiment.

Parameters:

• physical_qubits (Tuple[int, int]) – Two-value tuple of qubit indices on which to run tomography. The first index stands for the control qubit.

• flat_top_widths (Optional[Iterable[float]]) – Deprecated. The total duration of the square part of cross resonance pulse(s) to scan, in units of dt. The total pulse duration including Gaussian rising and falling edges is implicitly computed with experiment parameters sigma and risefall.

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

• cr_gate (Optional[Type[Gate]]) – Optional, circuit gate class representing the cross resonance pulse. Providing this object allows us to run this experiment with circuit simulator, and this object might be used for testing, development of analysis protocol, and educational purpose without needing to wait for hardware queueing. Note that this instance must provide matrix representation, such as unitary gate or Hamiltonian gate, and the class is expected to be instantiated with a single parameter width in units of sec.

• durations (Optional[Sequence[int]]) – Optional. The total duration of cross resonance pulse(s) including rising and falling edges. The minimum number should be larger than the total lengths of these ramps. If not provided, then num_durations evenly spaced durations between min_durations and max_durations are automatically generated from these experiment options. The default numbers are chosen to have a good sensitivity for the Hamiltonian coefficient of interest at the rate around 1 MHz. This argument should be provided in units of sec.

• kwargs – Pulse parameters. See experiment_options() for details.

Raises:

QiskitError – When qubits length is not 2.

Attributes

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

Methods

EchoedCrossResonanceHamiltonian.circuits()	Return a list of experiment circuits.
EchoedCrossResonanceHamiltonian.config()	Return the config dataclass for this experiment
EchoedCrossResonanceHamiltonian.copy()	Return a copy of the experiment
EchoedCrossResonanceHamiltonian.from_config(config)	Initialize an experiment from experiment config
EchoedCrossResonanceHamiltonian.run([...])	Run an experiment and perform analysis.
EchoedCrossResonanceHamiltonian.set_experiment_options(...)	Set the experiment options.
EchoedCrossResonanceHamiltonian.set_run_options(...)	Set options values for the experiment run() method.
EchoedCrossResonanceHamiltonian.set_transpile_options(...)	Set the transpiler options for run() method.