fix: removed toplevel cuquantum import

src/qibotn/backends/cutensornet.py

@@ -1,19 +1,9 @@
-import cuquantum  # pylint: disable=import-error
 import numpy as np
 from qibo.backends.numpy import NumpyBackend
 from qibo.config import raise_error
 from qibo.result import QuantumState
 
-CUDA_TYPES = {
-    "complex64": (
-        cuquantum.cudaDataType.CUDA_C_32F,
-        cuquantum.ComputeType.COMPUTE_32F,
-    ),
-    "complex128": (
-        cuquantum.cudaDataType.CUDA_C_64F,
-        cuquantum.ComputeType.COMPUTE_64F,
-    ),
-}
+CUDA_TYPES = {}
 
 
 class CuTensorNet(NumpyBackend):  # pragma: no cover
@@ -75,6 +65,18 @@ def __init__(self, runcard):
         self.supports_multigpu = True
         self.handle = self.cutn.create()
 
+        global CUDA_TYPES
+        CUDA_TYPES = {
+            "complex64": (
+                self.cuquantum.cudaDataType.CUDA_C_32F,
+                self.cuquantum.ComputeType.COMPUTE_32F,
+            ),
+            "complex128": (
+                self.cuquantum.cudaDataType.CUDA_C_64F,
+                self.cuquantum.ComputeType.COMPUTE_64F,
+            ),
+        }
+
     def apply_gate(self, gate, state, nqubits):  # pragma: no cover
         raise_error(NotImplementedError, "QiboTN cannot apply gates directly.")