ResonatorSpectroscopy¶

class ResonatorSpectroscopy(physical_qubits, backend=None, frequencies=None, absolute=True, **experiment_options)[source]¶

An experiment to perform frequency spectroscopy of the readout resonator.

Warning

Some backends may not have the required functionality to properly support resonator spectroscopy experiments. The experiment may not work or the resulting resonance may not properly reflect the properties of the readout resonator.

Overview

This experiment does spectroscopy on the readout resonator. It applies the following circuit

     ┌─┐
  q: ┤M├
     └╥┘
c: 1/═╩═
      0

where a spectroscopy pulse is attached to the measurement instruction. An initial circuit can be added before the measurement by setting the initial_circuit experiment option. If set, the experiment applies the following circuit:

     ┌─────────────────┐┌─┐
  q: ┤ initial_circuit ├┤M├
     └─────────────────┘└╥┘
c: 1/════════════════════╩═
                         0

Side note 1: when doing readout resonator spectroscopy, each measured IQ point has a frequency dependent phase. Close to the resonance, the IQ points start rotating around in the IQ plan. This effect must be accounted for in the data processing to produce a meaningful signal. The default data processing workflow will therefore reduce the two- dimensional IQ data to one-dimensional data using the magnitude of each IQ point.

Side node 2: when running readout resonator spectroscopy in a parallel experiment the user will need to specify the memory slot to use. This can easily be done with the code shown below.

specs = []
for slot, qubit in enumerate(qubits):
    specs.append(ResonatorSpectroscopy(
        physical_qubits=[qubit],
        backend=backend2,
        memory_slot=slot,
    ))

exp = ParallelExperiment(specs, backend=backend2)

Analysis class reference

ResonatorSpectroscopyAnalysis

Experiment options

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

Options

Defined in the class ResonatorSpectroscopy:
- amp (float)
  
  Default value: 1
  
  The amplitude of the spectroscopy pulse. Defaults to 1 and must be between 0 and 1.
- duration (float)
  
  Default value: 4.8e-07
  
  The duration in seconds of the spectroscopy pulse.
- sigma (float)
  
  Default value: 6e-08
  
  The standard deviation of the spectroscopy pulse in seconds.
- width (float)
  
  Default value: 3.6e-07
  
  The width of the flat-top part of the GaussianSquare pulse in seconds.
- initial_circuit (QuantumCircuit)
  
  Default value: None
  
  A single-qubit initial circuit to run before the measurement/spectroscopy pulse. The circuit must contain only a single qubit and zero classical bits. If None, no circuit is appended before the measurement. Defaults to None.
- memory_slot (int)
  
  Default value: 0
  
  The memory slot that the acquire instruction uses in the pulse schedule. The default value is 0. This argument allows the experiment to function in a ParallelExperiment.
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.

Example

The resonator spectroscopy experiment can be run by doing:

qubit = 1
spec = ResonatorSpectroscopy([qubit], backend)
exp_data = spec.run().block_for_results()
exp_data.figure(0)

This will measure the resonator attached to qubit 1 and report the resonance frequency as well as the kappa, i.e. the line width, of the resonator.