class EchoedCrossResonanceHamiltonian(physical_qubits, backend=None, cr_gate=None, durations=None, **kwargs)[source]#

Echoed cross resonance Hamiltonian tomography experiment.


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.


[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


Experiment options

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

  • Defined in the class CrossResonanceHamiltonian:

    • 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


Create a new experiment.

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

  • backend (Backend | None) – Optional, the backend to run the experiment on.

  • cr_gate (Type[Gate] | None) – 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 (Sequence[int] | None) – 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.


QiskitError – When qubits length is not 2.



Return the analysis instance for the experiment


Return the backend for the experiment


Return the options for the experiment.


Return experiment type.

num_pulses = 2#

Return the number of qubits for the experiment.


Return the device qubits for the experiment.


Return options values for the experiment run() method.


Return the transpiler options for the run() method.



Return a list of experiment circuits.


A list of QuantumCircuit.


QiskitError – When the backend is not set and cr gate is CRPulseGate type.

Return type:



Return the config dataclass for this experiment

Return type:



Return a copy of the experiment

Return type:


classmethod from_config(config)#

Initialize an experiment from experiment config

Return type:



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


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


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:



QiskitError – if backend is not specified.

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

Run an experiment and perform analysis.

  • 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.


The experiment data object.


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

Return type:



Set the experiment options.


fields – The fields to update the options


AttributeError – If the field passed in is not a supported options


Set options values for the experiment run() method.


fields – The fields to update the options

See also

The Setting options for your experiment guide for code example.


Set the transpiler options for run() method.


fields – The fields to update the options


QiskitError – If initial_layout is one of the fields.

See also

The Setting options for your experiment guide for code example.