Fix bug that caused XEB to fail when requesting depth > 100. (#6671)

* Pass max_cycle_depth to generate_library_of_2q_circuits

* update default cycle depths

* update default depths

* Make notebook more robust to numerical errors

Author: eliottrosenberg

cirq-core/cirq/experiments/two_qubit_xeb.py

@@ -354,7 +354,7 @@ def parallel_xeb_workflow(
     n_repetitions: int = 10**4,
     n_combinations: int = 10,
     n_circuits: int = 20,
-    cycle_depths: Sequence[int] = tuple(np.arange(3, 100, 20)),
+    cycle_depths: Sequence[int] = (5, 25, 50, 100, 200, 300),
     random_state: 'cirq.RANDOM_STATE_OR_SEED_LIKE' = None,
     ax: Optional[plt.Axes] = None,
     **plot_kwargs,
@@ -402,7 +402,10 @@ def parallel_xeb_workflow(
         ax.plot(**plot_kwargs)
 
     circuit_library = rqcg.generate_library_of_2q_circuits(
-        n_library_circuits=n_circuits, two_qubit_gate=entangling_gate, random_state=rs
+        n_library_circuits=n_circuits,
+        two_qubit_gate=entangling_gate,
+        random_state=rs,
+        max_cycle_depth=max(cycle_depths),
     )
 
     combs_by_layer = rqcg.get_random_combinations_for_device(
@@ -435,7 +438,7 @@ def parallel_two_qubit_xeb(
     n_repetitions: int = 10**4,
     n_combinations: int = 10,
     n_circuits: int = 20,
-    cycle_depths: Sequence[int] = tuple(np.arange(3, 100, 20)),
+    cycle_depths: Sequence[int] = (5, 25, 50, 100, 200, 300),
     random_state: 'cirq.RANDOM_STATE_OR_SEED_LIKE' = None,
     ax: Optional[plt.Axes] = None,
     **plot_kwargs,
@@ -483,7 +486,7 @@ def run_rb_and_xeb(
         np.logspace(np.log10(5), np.log10(1000), 5, dtype=int)
     ),
     entangling_gate: 'cirq.Gate' = ops.CZ,
-    depths_xeb: Sequence[int] = tuple(np.arange(3, 100, 20)),
+    depths_xeb: Sequence[int] = (5, 25, 50, 100, 200, 300),
     xeb_combinations: int = 10,
     random_state: 'cirq.RANDOM_STATE_OR_SEED_LIKE' = None,
 ) -> InferredXEBResult:

docs/noise/qcvv/parallel_xeb.ipynb

@@ -111,8 +111,8 @@
     "# Simulation\n",
     "qubits = cirq.GridQubit.rect(3, 2, 4, 3)\n",
     "result = cirq.experiments.parallel_two_qubit_xeb(\n",
-    "    sampler=cirq.DensityMatrixSimulator(noise=cirq.depolarize(5e-3)),  # Any simulator or a ProcessorSampler.\n",
-    "    qubits=qubits \n",
+    "    sampler=cirq.DensityMatrixSimulator(noise=cirq.depolarize(5e-3), dtype=np.complex128),  # Any simulator or a ProcessorSampler.\n",
+    "    qubits=qubits\n",
     ")"
    ]
   },
@@ -554,7 +554,8 @@
    "toc_visible": true
   },
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
    "name": "python3"
   },
   "language_info": {
@@ -567,9 +568,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.13"
+   "version": "3.11.8"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 4
 }