Rabi content has been moved to ReCirq: Delete the items in Cirq (quantumlib#5448)

Rabi Oscillations have been moved per quantumlib/ReCirq#292.
Also update the intro notebook to not use now-moved recirq experiment (replaced with single_qubit_state_tomography)
Also ran a formatter and cleared outputs from intro notebook

Only merge with redirect cl/452988155

Author: augustehirth

cirq-core/cirq/experiments/__init__.py

@@ -20,8 +20,6 @@
 )
 
 from cirq.experiments.qubit_characterizations import (
-    rabi_oscillations,
-    RabiResult,
     RandomizedBenchMarkResult,
     single_qubit_randomized_benchmarking,
     single_qubit_state_tomography,

cirq-core/cirq/experiments/qubit_characterizations.py

@@ -17,13 +17,12 @@
 
 from typing import Any, Iterator, List, Optional, Sequence, Tuple, TYPE_CHECKING
 import numpy as np
-import sympy
 
 from matplotlib import pyplot as plt
 
 # this is for older systems with matplotlib <3.2 otherwise 3d projections fail
 from mpl_toolkits import mplot3d  # pylint: disable=unused-import
-from cirq import circuits, ops, protocols, study
+from cirq import circuits, ops, protocols
 
 if TYPE_CHECKING:
     import cirq
@@ -54,52 +53,6 @@ class Cliffords:
     s1_y: List[List[ops.Gate]]
 
 
-class RabiResult:
-    """Results from a Rabi oscillation experiment."""
-
-    def __init__(self, rabi_angles: Sequence[float], excited_state_probabilities: Sequence[float]):
-        """Inits RabiResult.
-
-        Args:
-            rabi_angles: The rotation angles of the qubit around the x-axis
-                of the Bloch sphere.
-            excited_state_probabilities: The corresponding probabilities that
-                the qubit is in the excited state.
-        """
-        self._rabi_angles = rabi_angles
-        self._excited_state_probs = excited_state_probabilities
-
-    @property
-    def data(self) -> Sequence[Tuple[float, float]]:
-        """Returns a sequence of tuple pairs with the first item being a Rabi
-        angle and the second item being the corresponding excited state
-        probability.
-        """
-        return [(angle, prob) for angle, prob in zip(self._rabi_angles, self._excited_state_probs)]
-
-    def plot(self, ax: Optional[plt.Axes] = None, **plot_kwargs: Any) -> plt.Axes:
-        """Plots excited state probability vs the Rabi angle (angle of rotation
-        around the x-axis).
-
-        Args:
-            ax: the plt.Axes to plot on. If not given, a new figure is created,
-                plotted on, and shown.
-            **plot_kwargs: Arguments to be passed to 'plt.Axes.plot'.
-        Returns:
-            The plt.Axes containing the plot.
-        """
-        show_plot = not ax
-        if not ax:
-            fig, ax = plt.subplots(1, 1, figsize=(8, 8))
-        ax.set_ylim([0, 1])
-        ax.plot(self._rabi_angles, self._excited_state_probs, 'ro-', **plot_kwargs)
-        ax.set_xlabel(r"Rabi Angle (Radian)")
-        ax.set_ylabel('Excited State Probability')
-        if show_plot:
-            fig.show()
-        return ax
-
-
 class RandomizedBenchMarkResult:
     """Results from a randomized benchmarking experiment."""
 
@@ -216,45 +169,6 @@ def plot(self, axes: Optional[List[plt.Axes]] = None, **plot_kwargs: Any) -> Lis
         return axes
 
 
-def rabi_oscillations(
-    sampler: 'cirq.Sampler',
-    qubit: 'cirq.Qid',
-    max_angle: float = 2 * np.pi,
-    *,
-    repetitions: int = 1000,
-    num_points: int = 200,
-) -> RabiResult:
-    """Runs a Rabi oscillation experiment.
-
-    Rotates a qubit around the x-axis of the Bloch sphere by a sequence of Rabi
-    angles evenly spaced between 0 and max_angle. For each rotation, repeat
-    the circuit a number of times and measure the average probability of the
-    qubit being in the |1> state.
-
-    Args:
-        sampler: The quantum engine or simulator to run the circuits.
-        qubit: The qubit under test.
-        max_angle: The final Rabi angle in radians.
-        repetitions: The number of repetitions of the circuit for each Rabi
-            angle.
-        num_points: The number of Rabi angles.
-
-    Returns:
-        A RabiResult object that stores and plots the result.
-    """
-    theta = sympy.Symbol('theta')
-    circuit = circuits.Circuit(ops.X(qubit) ** theta)
-    circuit.append(ops.measure(qubit, key='z'))
-    sweep = study.Linspace(key='theta', start=0.0, stop=max_angle / np.pi, length=num_points)
-    results = sampler.run_sweep(circuit, params=sweep, repetitions=repetitions)
-    angles = np.linspace(0.0, max_angle, num_points)
-    excited_state_probs = np.zeros(num_points)
-    for i in range(num_points):
-        excited_state_probs[i] = np.mean(results[i].measurements['z'])
-
-    return RabiResult(angles, excited_state_probs)
-
-
 def single_qubit_randomized_benchmarking(
     sampler: 'cirq.Sampler',
     qubit: 'cirq.Qid',

cirq-core/cirq/experiments/qubit_characterizations_test.py

@@ -22,28 +22,13 @@
 from cirq import GridQubit
 from cirq import circuits, ops, sim
 from cirq.experiments import (
-    rabi_oscillations,
     single_qubit_randomized_benchmarking,
     two_qubit_randomized_benchmarking,
     single_qubit_state_tomography,
     two_qubit_state_tomography,
 )
 
 
-def test_rabi_oscillations():
-    # Check that the excited state population matches the ideal case within a
-    # small statistical error.
-    simulator = sim.Simulator()
-    qubit = GridQubit(0, 0)
-    results = rabi_oscillations(simulator, qubit, np.pi, repetitions=1000)
-    data = np.asarray(results.data)
-    angles = data[:, 0]
-    actual_pops = data[:, 1]
-    target_pops = 0.5 - 0.5 * np.cos(angles)
-    rms_err = np.sqrt(np.mean((target_pops - actual_pops) ** 2))
-    assert rms_err < 0.1
-
-
 def test_single_qubit_cliffords():
     I = np.eye(2)
     X = np.array([[0, 1], [1, 0]])

docs/tutorials/_index.yaml

@@ -43,11 +43,6 @@ landing_page:
         path: /cirq/tutorials/hidden_linear_function
         icon:
           name: menu_book
-      - heading: Rabi oscillation experiment
-        description: Example of using sweeps and symbols to show rotation of a qubit by different angles.
-        path: /cirq/tutorials/rabi_oscillations
-        icon:
-          name: menu_book
       - heading: Shor's algorithm
         description: Factor numbers using a quantum computer.
         path: /cirq/tutorials/shor