|
| 1 | +# This code is part of Qiskit. |
| 2 | +# |
| 3 | +# (C) Copyright IBM 2021. |
| 4 | +# |
| 5 | +# This code is licensed under the Apache License, Version 2.0. You may |
| 6 | +# obtain a copy of this license in the LICENSE.txt file in the root directory |
| 7 | +# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0. |
| 8 | +# |
| 9 | +# Any modifications or derivative works of this code must retain this |
| 10 | +# copyright notice, and modified files need to carry a notice indicating |
| 11 | +# that they have been altered from the originals. |
| 12 | + |
| 13 | +"""Rabi amplitude experiment.""" |
| 14 | + |
| 15 | +from typing import Any, Dict, List, Optional, Union |
| 16 | +import numpy as np |
| 17 | + |
| 18 | +from qiskit import QiskitError, QuantumCircuit |
| 19 | +from qiskit.circuit import Gate, Parameter |
| 20 | +from qiskit.qobj.utils import MeasLevel |
| 21 | +from qiskit.providers import Backend |
| 22 | +import qiskit.pulse as pulse |
| 23 | +from qiskit.providers.options import Options |
| 24 | + |
| 25 | +from qiskit_experiments.analysis import ( |
| 26 | + CurveAnalysis, |
| 27 | + CurveAnalysisResult, |
| 28 | + SeriesDef, |
| 29 | + fit_function, |
| 30 | + get_opt_value, |
| 31 | + get_opt_error, |
| 32 | +) |
| 33 | +from qiskit_experiments.base_experiment import BaseExperiment |
| 34 | +from qiskit_experiments.data_processing.processor_library import get_to_signal_processor |
| 35 | + |
| 36 | + |
| 37 | +class RabiAnalysis(CurveAnalysis): |
| 38 | + r"""Rabi analysis class based on a fit to a cosine function. |
| 39 | +
|
| 40 | + Analyse a Rabi experiment by fitting it to a cosine function |
| 41 | +
|
| 42 | + .. math:: |
| 43 | + y = amp \cos\left(2 \pi {\rm freq} x + {\rm phase}\right) + baseline |
| 44 | +
|
| 45 | + Fit Parameters |
| 46 | + - :math:`amp`: Amplitude of the oscillation. |
| 47 | + - :math:`baseline`: Base line. |
| 48 | + - :math:`{\rm freq}`: Frequency of the oscillation. This is the fit parameter of interest. |
| 49 | + - :math:`{\rm phase}`: Phase of the oscillation. |
| 50 | +
|
| 51 | + Initial Guesses |
| 52 | + - :math:`amp`: The maximum y value less the minimum y value. |
| 53 | + - :math:`baseline`: The average of the data. |
| 54 | + - :math:`{\rm freq}`: The frequency with the highest power spectral density. |
| 55 | + - :math:`{\rm phase}`: Zero. |
| 56 | +
|
| 57 | + Bounds |
| 58 | + - :math:`amp`: [-2, 2] scaled to the maximum signal value. |
| 59 | + - :math:`baseline`: [-1, 1] scaled to the maximum signal value. |
| 60 | + - :math:`{\rm freq}`: [0, inf]. |
| 61 | + - :math:`{\rm phase}`: [-pi, pi]. |
| 62 | + """ |
| 63 | + |
| 64 | + __series__ = [ |
| 65 | + SeriesDef( |
| 66 | + fit_func=lambda x, amp, freq, phase, baseline: fit_function.cos( |
| 67 | + x, amp=amp, freq=freq, phase=phase, baseline=baseline |
| 68 | + ), |
| 69 | + plot_color="blue", |
| 70 | + ) |
| 71 | + ] |
| 72 | + |
| 73 | + @classmethod |
| 74 | + def _default_options(cls): |
| 75 | + """Return the default analysis options. |
| 76 | +
|
| 77 | + See :meth:`~qiskit_experiment.analysis.CurveAnalysis._default_options` for |
| 78 | + descriptions of analysis options. |
| 79 | + """ |
| 80 | + default_options = super()._default_options() |
| 81 | + default_options.p0 = {"amp": None, "freq": None, "phase": None, "baseline": None} |
| 82 | + default_options.bounds = {"amp": None, "freq": None, "phase": None, "baseline": None} |
| 83 | + default_options.fit_reports = {"freq": "rate"} |
| 84 | + default_options.xlabel = "Amplitude" |
| 85 | + default_options.ylabel = "Signal (arb. units)" |
| 86 | + |
| 87 | + return default_options |
| 88 | + |
| 89 | + def _setup_fitting(self, **options) -> Union[Dict[str, Any], List[Dict[str, Any]]]: |
| 90 | + """Fitter options.""" |
| 91 | + user_p0 = self._get_option("p0") |
| 92 | + user_bounds = self._get_option("bounds") |
| 93 | + |
| 94 | + max_abs_y = np.max(np.abs(self._data().y)) |
| 95 | + |
| 96 | + # Use a fast Fourier transform to guess the frequency. |
| 97 | + fft = np.abs(np.fft.fft(self._data().y - np.average(self._data().y))) |
| 98 | + damp = self._data().x[1] - self._data().x[0] |
| 99 | + freqs = np.linspace(0.0, 1.0 / (2.0 * damp), len(fft)) |
| 100 | + |
| 101 | + b_guess = np.average(self._data().y) |
| 102 | + a_guess = np.max(self._data().y) - np.min(self._data().y) - b_guess |
| 103 | + f_guess = freqs[np.argmax(fft[0 : len(fft) // 2])] |
| 104 | + |
| 105 | + if user_p0["phase"] is not None: |
| 106 | + p_guesses = [user_p0["phase"]] |
| 107 | + else: |
| 108 | + p_guesses = [0, np.pi / 4, np.pi / 2, 3 * np.pi / 4, np.pi] |
| 109 | + |
| 110 | + fit_options = [] |
| 111 | + for p_guess in p_guesses: |
| 112 | + fit_option = { |
| 113 | + "p0": { |
| 114 | + "amp": user_p0["amp"] or a_guess, |
| 115 | + "freq": user_p0["freq"] or f_guess, |
| 116 | + "phase": p_guess, |
| 117 | + "baseline": user_p0["baseline"] or b_guess, |
| 118 | + }, |
| 119 | + "bounds": { |
| 120 | + "amp": user_bounds["amp"] or (-2 * max_abs_y, 2 * max_abs_y), |
| 121 | + "freq": user_bounds["freq"] or (0, np.inf), |
| 122 | + "phase": user_bounds["phase"] or (-np.pi, np.pi), |
| 123 | + "baseline": user_bounds["baseline"] or (-1 * max_abs_y, 1 * max_abs_y), |
| 124 | + }, |
| 125 | + } |
| 126 | + fit_option.update(options) |
| 127 | + fit_options.append(fit_option) |
| 128 | + |
| 129 | + return fit_options |
| 130 | + |
| 131 | + def _post_analysis(self, analysis_result: CurveAnalysisResult) -> CurveAnalysisResult: |
| 132 | + """Algorithmic criteria for whether the fit is good or bad. |
| 133 | +
|
| 134 | + A good fit has: |
| 135 | + - a reduced chi-squared lower than three, |
| 136 | + - more than a quarter of a full period, |
| 137 | + - less than 10 full periods, and |
| 138 | + - an error on the fit frequency lower than the fit frequency. |
| 139 | + """ |
| 140 | + fit_freq = get_opt_value(analysis_result, "freq") |
| 141 | + fit_freq_err = get_opt_error(analysis_result, "freq") |
| 142 | + |
| 143 | + criteria = [ |
| 144 | + analysis_result["reduced_chisq"] < 3, |
| 145 | + 1.0 / 4.0 < fit_freq < 10.0, |
| 146 | + (fit_freq_err is None or (fit_freq_err < fit_freq)), |
| 147 | + ] |
| 148 | + |
| 149 | + if all(criteria): |
| 150 | + analysis_result["quality"] = "computer_good" |
| 151 | + else: |
| 152 | + analysis_result["quality"] = "computer_bad" |
| 153 | + |
| 154 | + return analysis_result |
| 155 | + |
| 156 | + |
| 157 | +class Rabi(BaseExperiment): |
| 158 | + """An experiment that scans the amplitude of a pulse to calibrate rotations between 0 and 1. |
| 159 | +
|
| 160 | + The circuits that are run have a custom rabi gate with the pulse schedule attached to it |
| 161 | + through the calibrations. The circuits are of the form: |
| 162 | +
|
| 163 | + .. parsed-literal:: |
| 164 | +
|
| 165 | + ┌───────────┐ ░ ┌─┐ |
| 166 | + q_0: ┤ Rabi(amp) ├─░─┤M├ |
| 167 | + └───────────┘ ░ └╥┘ |
| 168 | + measure: 1/═════════════════╩═ |
| 169 | + 0 |
| 170 | +
|
| 171 | + """ |
| 172 | + |
| 173 | + __analysis_class__ = RabiAnalysis |
| 174 | + |
| 175 | + @classmethod |
| 176 | + def _default_run_options(cls) -> Options: |
| 177 | + """Default option values for the experiment :meth:`run` method.""" |
| 178 | + return Options( |
| 179 | + meas_level=MeasLevel.KERNELED, |
| 180 | + meas_return="single", |
| 181 | + ) |
| 182 | + |
| 183 | + @classmethod |
| 184 | + def _default_experiment_options(cls) -> Options: |
| 185 | + """Default values for the pulse if no schedule is given. |
| 186 | +
|
| 187 | + Users can set a schedule by doing |
| 188 | +
|
| 189 | + .. code-block:: |
| 190 | +
|
| 191 | + rabi.set_experiment_options(schedule=rabi_schedule) |
| 192 | +
|
| 193 | + """ |
| 194 | + return Options( |
| 195 | + duration=160, |
| 196 | + sigma=40, |
| 197 | + amplitudes=np.linspace(-0.95, 0.95, 51), |
| 198 | + schedule=None, |
| 199 | + normalization=True, |
| 200 | + ) |
| 201 | + |
| 202 | + def __init__(self, qubit: int): |
| 203 | + """Setup a Rabi experiment on the given qubit. |
| 204 | +
|
| 205 | + Args: |
| 206 | + qubit: The qubit on which to run the Rabi experiment. |
| 207 | + """ |
| 208 | + super().__init__([qubit]) |
| 209 | + |
| 210 | + def circuits(self, backend: Optional[Backend] = None) -> List[QuantumCircuit]: |
| 211 | + """Create the circuits for the Rabi experiment. |
| 212 | +
|
| 213 | + Args: |
| 214 | + backend: A backend object. |
| 215 | +
|
| 216 | + Returns: |
| 217 | + A list of circuits with a rabi gate with an attached schedule. Each schedule |
| 218 | + will have a different value of the scanned amplitude. |
| 219 | +
|
| 220 | + Raises: |
| 221 | + QiskitError: |
| 222 | + - If the user-provided schedule does not contain a channel with an index |
| 223 | + that matches the qubit on which to run the Rabi experiment. |
| 224 | + - If the user provided schedule has more than one free parameter. |
| 225 | + """ |
| 226 | + # TODO this is temporary logic. Need update of circuit data and processor logic. |
| 227 | + self.set_analysis_options( |
| 228 | + data_processor=get_to_signal_processor( |
| 229 | + meas_level=self.run_options.meas_level, |
| 230 | + meas_return=self.run_options.meas_return, |
| 231 | + normalize=self.experiment_options.normalization, |
| 232 | + ) |
| 233 | + ) |
| 234 | + |
| 235 | + schedule = self.experiment_options.get("schedule", None) |
| 236 | + |
| 237 | + if schedule is None: |
| 238 | + amp = Parameter("amp") |
| 239 | + with pulse.build() as default_schedule: |
| 240 | + pulse.play( |
| 241 | + pulse.Gaussian( |
| 242 | + duration=self.experiment_options.duration, |
| 243 | + amp=amp, |
| 244 | + sigma=self.experiment_options.sigma, |
| 245 | + ), |
| 246 | + pulse.DriveChannel(self.physical_qubits[0]), |
| 247 | + ) |
| 248 | + |
| 249 | + schedule = default_schedule |
| 250 | + else: |
| 251 | + if self.physical_qubits[0] not in set(ch.index for ch in schedule.channels): |
| 252 | + raise QiskitError( |
| 253 | + f"User provided schedule {schedule.name} does not contain a channel " |
| 254 | + "for the qubit on which to run Rabi." |
| 255 | + ) |
| 256 | + |
| 257 | + if len(schedule.parameters) != 1: |
| 258 | + raise QiskitError("Schedule in Rabi must have exactly one free parameter.") |
| 259 | + |
| 260 | + param = next(iter(schedule.parameters)) |
| 261 | + |
| 262 | + gate = Gate(name="Rabi", num_qubits=1, params=[param]) |
| 263 | + |
| 264 | + circuit = QuantumCircuit(1) |
| 265 | + circuit.append(gate, (0,)) |
| 266 | + circuit.measure_active() |
| 267 | + circuit.add_calibration(gate, (self.physical_qubits[0],), schedule, params=[param]) |
| 268 | + |
| 269 | + circs = [] |
| 270 | + for amp in self.experiment_options.amplitudes: |
| 271 | + amp = np.round(amp, decimals=6) |
| 272 | + assigned_circ = circuit.assign_parameters({param: amp}, inplace=False) |
| 273 | + assigned_circ.metadata = { |
| 274 | + "experiment_type": self._type, |
| 275 | + "qubit": self.physical_qubits[0], |
| 276 | + "xval": amp, |
| 277 | + "unit": "arb. unit", |
| 278 | + "amplitude": amp, |
| 279 | + "schedule": str(schedule), |
| 280 | + } |
| 281 | + |
| 282 | + if backend: |
| 283 | + assigned_circ.metadata["dt"] = getattr(backend.configuration(), "dt", "n.a.") |
| 284 | + |
| 285 | + circs.append(assigned_circ) |
| 286 | + |
| 287 | + return circs |
0 commit comments