Remove deprecated experiments (quantumlib#5674)

    - Removes deprecated functions, classes, and modules from experiments.
    - CrossEntropyResult and CrossEntropyResult are still there since they
    need json backwards compatibility.  Will follow up with later PR for it.

Author: dstrain115

cirq/__init__.py

@@ -110,15 +110,10 @@
     estimate_parallel_single_qubit_readout_errors,
     estimate_single_qubit_readout_errors,
     hog_score_xeb_fidelity_from_probabilities,
-    least_squares_xeb_fidelity_from_expectations,
-    least_squares_xeb_fidelity_from_probabilities,
     linear_xeb_fidelity,
     linear_xeb_fidelity_from_probabilities,
     log_xeb_fidelity,
     log_xeb_fidelity_from_probabilities,
-    generate_boixo_2018_supremacy_circuits_v2,
-    generate_boixo_2018_supremacy_circuits_v2_bristlecone,
-    generate_boixo_2018_supremacy_circuits_v2_grid,
     measure_confusion_matrix,
     xeb_fidelity,
 )

cirq/experiments/__init__.py

@@ -13,12 +13,6 @@
 # limitations under the License.
 """Experiments and tools for characterizing quantum operations."""
 
-from cirq.experiments.google_v2_supremacy_circuit import (
-    generate_boixo_2018_supremacy_circuits_v2,
-    generate_boixo_2018_supremacy_circuits_v2_bristlecone,
-    generate_boixo_2018_supremacy_circuits_v2_grid,
-)
-
 from cirq.experiments.qubit_characterizations import (
     RandomizedBenchMarkResult,
     single_qubit_randomized_benchmarking,
@@ -28,29 +22,17 @@
     two_qubit_state_tomography,
 )
 
-from cirq.experiments.cross_entropy_benchmarking import (
-    build_entangling_layers,
-    cross_entropy_benchmarking,
-    CrossEntropyResult,
-    CrossEntropyResultDict,
-)
+from cirq.experiments.cross_entropy_benchmarking import CrossEntropyResult, CrossEntropyResultDict
 
 from cirq.experiments.fidelity_estimation import (
     hog_score_xeb_fidelity_from_probabilities,
-    least_squares_xeb_fidelity_from_expectations,
-    least_squares_xeb_fidelity_from_probabilities,
-    linear_xeb_fidelity,
     linear_xeb_fidelity_from_probabilities,
+    linear_xeb_fidelity,
     log_xeb_fidelity,
     log_xeb_fidelity_from_probabilities,
     xeb_fidelity,
 )
 
-from cirq.experiments.grid_parallel_two_qubit_xeb import (
-    collect_grid_parallel_two_qubit_xeb_data,
-    compute_grid_parallel_two_qubit_xeb_results,
-)
-
 from cirq.experiments.purity_estimation import purity_from_probabilities
 
 from cirq.experiments.random_quantum_circuit_generation import (