Add docstrings

src/qibotn/mps_utils.py

@@ -2,11 +2,10 @@ import cupy as cp
 from cuquantum import contract
 from cuquantum.cutensornet.experimental import contract_decompose
 
-# Reference: https://github.com/NVIDIA/cuQuantum/blob/main/python/samples/cutensornet/tn_algorithms/mps_algorithms.ipynb
 
 
 def initial(num_qubits, dtype):
-    r"""Generate the MPS with an initial state of :math:`\ket{00...00}`"""
+    """Generate the MPS with an initial state of :math:`\ket{00...00}`"""
     state_tensor = cp.asarray([1, 0], dtype=dtype).reshape(1, 2, 1)
     mps_tensors = [state_tensor] * num_qubits
     return mps_tensors
@@ -27,7 +26,9 @@ def mps_site_right_swap(mps_tensors, i, **kwargs):
 
 def apply_gate(mps_tensors, gate, qubits, **kwargs):
     """Apply the gate operand to the MPS tensors in-place.
-
+    
+    # Reference: https://github.com/NVIDIA/cuQuantum/blob/main/python/samples/cutensornet/tn_algorithms/mps_algorithms.ipynb
+    
     Args:
         mps_tensors: A list of rank-3 ndarray-like tensor objects.
             The indices of the ith tensor are expected to be the bonding index to the i-1 tensor,