diff --git a/src/qibotn/backends/cutensornet.py b/src/qibotn/backends/cutensornet.py
index fc010e9..05f45af 100644
--- a/src/qibotn/backends/cutensornet.py
+++ b/src/qibotn/backends/cutensornet.py
@@ -18,7 +18,9 @@ CUDA_TYPES = {
 
 class CuTensorNet(NumpyBackend):  # pragma: no cover
     # CI does not test for GPU
+    """Creates CuQuantum backend for QiboTN.
 
+    """
     def __init__(self, runcard):
         super().__init__()
         from cuquantum import cutensornet as cutn  # pylint: disable=import-error
@@ -92,6 +94,17 @@ class CuTensorNet(NumpyBackend):  # pragma: no cover
             super().set_precision(precision)
 
     def cuda_type(self, dtype="complex64"):
+        """Get CUDA Type
+
+        Args:
+            dtype (str, optional): Either single ("complex64") or double (complex128) precision. Defaults to "complex64".
+
+        Raises:
+            TypeError: dtype either complex64 or complex128
+
+        Returns:
+            CUDA Type: tuple of cuquantum.cudaDataType and cuquantum.ComputeType
+        """
         if dtype in CUDA_TYPES:
             return CUDA_TYPES[dtype]
         else:
@@ -100,7 +113,7 @@ class CuTensorNet(NumpyBackend):  # pragma: no cover
     def execute_circuit(
         self, circuit, initial_state=None, nshots=None, return_array=False
     ):  # pragma: no cover
-        """Executes a quantum circuit.
+        """Executes a quantum circuit using selected TN backend.
 
         Args:
             circuit (:class:`qibo.models.circuit.Circuit`): Circuit to execute.
@@ -108,7 +121,7 @@ class CuTensorNet(NumpyBackend):  # pragma: no cover
                 If ``None`` the default ``|00...0>`` state is used.
 
         Returns:
-            xxx.
+            QuantumState if return_array=False. Numpy array if return_array=True.
         """
 
         import qibotn.eval as eval
diff --git a/src/qibotn/circuit_convertor.py b/src/qibotn/circuit_convertor.py
index 14af79d..a15e533 100644
--- a/src/qibotn/circuit_convertor.py
+++ b/src/qibotn/circuit_convertor.py
@@ -26,6 +26,11 @@ class QiboCircuitToEinsum:
         self.circuit = circuit
 
     def state_vector_operands(self):
+        """Create the operands for expectation computation in the interleave format.
+
+        Returns:
+            Operands for the contraction in the interleave format.
+        """
         input_bitstring = "0" * len(self.active_qubits)
 
         input_operands = self._get_bitstring_tensors(input_bitstring)
@@ -84,6 +89,17 @@ class QiboCircuitToEinsum:
         return (2, 2) * nqubits
 
     def init_intermediate_circuit(self, circuit):
+        """Initialize the intermediate circuit representation.
+
+        This method initializes the intermediate circuit representation by extracting gate matrices and qubit IDs
+        from the given quantum circuit.
+
+        Parameters:
+            circuit (object): The quantum circuit object.
+
+        Returns:
+            None
+        """
         self.gate_tensors = []
         gates_qubits = []
 
@@ -105,6 +121,18 @@ class QiboCircuitToEinsum:
         self.active_qubits = np.unique(gates_qubits)
 
     def init_basis_map(self, backend, dtype):
+        """Initialize the basis map for the quantum circuit.
+
+        This method initializes a basis map for the quantum circuit, which maps binary
+        strings representing qubit states to their corresponding quantum state vectors.
+
+        Parameters:
+            backend (object): The backend object providing the array conversion method.
+            dtype (object): The data type for the quantum state vectors.
+
+        Returns:
+            None
+        """
         asarray = backend.asarray
         state_0 = asarray([1, 0], dtype=dtype)
         state_1 = asarray([0, 1], dtype=dtype)
@@ -112,6 +140,17 @@ class QiboCircuitToEinsum:
         self.basis_map = {"0": state_0, "1": state_1}
 
     def init_inverse_circuit(self, circuit):
+        """Initialize the inverse circuit representation.
+
+        This method initializes the inverse circuit representation by extracting gate matrices and qubit IDs
+        from the given quantum circuit.
+
+        Parameters:
+            circuit (object): The quantum circuit object.
+
+        Returns:
+            None
+        """
         self.gate_tensors_inverse = []
         gates_qubits_inverse = []
 
@@ -159,6 +198,14 @@ class QiboCircuitToEinsum:
         return gates
 
     def expectation_operands(self, pauli_string):
+        """Create the operands for pauli string expectation computation in the interleave format.
+
+        Args:
+            pauli_string: A string representating the list of pauli gates.
+
+        Returns:
+            Operands for the contraction in the interleave format.
+        """
         input_bitstring = "0" * self.circuit.nqubits
 
         input_operands = self._get_bitstring_tensors(input_bitstring)