MAHOUT-828 Add unit tests for single-qubit gates and swap test functionality (#837)

* Add unit tests for single-qubit gates and swap test functionality

- Implemented comprehensive tests for Pauli X, Y, Z, Hadamard, NOT, U, and T gates, ensuring correct state transitions and probabilities across different backends.
- Added edge case tests for single-qubit gates, including handling uninitialized circuits and invalid qubit indices.
- Introduced a swap test class to validate the behavior of swap tests with identical, orthogonal, and identical one states, including consistency checks across backends.
- Verified the existence and functionality of the CSWAP gate.

* Skip QDP tests if dependencies are not available in pytest configuration

Author: ryankert01

testing/conftest.py

@@ -0,0 +1,32 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+"""Shared pytest configuration and fixtures for all tests."""
+
+# Skip qdp tests if dependencies are not available
+collect_ignore_glob = []
+
+try:
+    import _qdp  # noqa: F401
+    import torch  # noqa: F401
+except ImportError:
+    collect_ignore_glob.append("qdp/*.py")
+
+
+def pytest_configure(config):
+    """Register custom markers."""
+    config.addinivalue_line("markers", "gpu: mark test as requiring GPU")

testing/qdp/__init__.py

@@ -0,0 +1,16 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#

qdp/qdp-python/tests/test_bindings.py testing/qdp/test_bindings.pyqdp/qdp-python/tests/test_bindings.py renamed to testing/qdp/test_bindings.py

@@ -0,0 +1,16 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#

…p/qdp-python/tests/test_high_fidelity.py testing/qdp/test_high_fidelity.pyqdp/qdp-python/tests/test_high_fidelity.py renamed to testing/qdp/test_high_fidelity.py qdp/qdp-python/tests/test_high_fidelity.py renamed to testing/qdp/test_high_fidelity.py

@@ -17,7 +17,7 @@
 
 import pytest
 
-from .utils import TESTING_BACKENDS, get_backend_config
+from ..utils import TESTING_BACKENDS, get_backend_config
 from qumat import QuMat
 
 

qdp/qdp-python/tests/test_numpy.py testing/qdp/test_numpy.pyqdp/qdp-python/tests/test_numpy.py renamed to testing/qdp/test_numpy.py

@@ -19,8 +19,8 @@
 import numpy as np
 from importlib import import_module
 
-from .utils import TESTING_BACKENDS
-from .utils.qumat_helpers import get_qumat_example_final_state_vector
+from ..utils import TESTING_BACKENDS
+from ..utils.qumat_helpers import get_qumat_example_final_state_vector
 
 
 @pytest.mark.parametrize("backend_name", TESTING_BACKENDS)

testing/qumat/__init__.py

@@ -17,7 +17,7 @@
 
 import pytest
 
-from .utils import TESTING_BACKENDS, get_backend_config, get_state_probability
+from ..utils import TESTING_BACKENDS, get_backend_config, get_state_probability
 from qumat import QuMat
 
 

testing/test_create_circuit.py testing/qumat/test_create_circuit.pytesting/test_create_circuit.py renamed to testing/qumat/test_create_circuit.py

@@ -18,7 +18,7 @@
 import pytest
 import numpy as np
 
-from .utils import TESTING_BACKENDS, get_backend_config
+from ..utils import TESTING_BACKENDS, get_backend_config
 from qumat import QuMat