Add mypy annotations (quantum_info)

qiskit/quantum_info/operators/symplectic/clifford.py

@@ -490,7 +490,7 @@ def _compose_general(cls, first: Clifford, second: Clifford) -> Clifford:
         return Clifford(data, validate=False, copy=False)
 
     @classmethod
-    def _compose_1q(cls, first, second) -> dict[tuple[bytes, bytes], Clifford]:
+    def _compose_1q(cls, first, second) -> Clifford:
         # 1-qubit composition can be done with a simple lookup table; there are 24 elements in the
         # 1q Clifford group, so 576 possible combinations, which is small enough to look up.
         if cls._COMPOSE_1Q_LOOKUP is None:

qiskit/quantum_info/operators/symplectic/pauli.py

@@ -155,7 +155,7 @@ class initialization (``Pauli('-iXYZ')``). A ``Pauli`` object can be
     _VALID_LABEL_PATTERN = re.compile(r"(?P<coeff>[+-]?1?[ij]?)(?P<pauli>[IXYZ]*)")
     _CANONICAL_PHASE_LABEL = {"": 0, "-i": 1, "-": 2, "i": 3}
 
-    def __init__(self, data: str | tuple | Pauli | ScalarOp | QuantumCircuit | None = None):
+    def __init__(self, data: str | tuple | BasePauli | ScalarOp | QuantumCircuit | None = None):
         """Initialize the Pauli.
 
         When using the symplectic array input data both z and x arguments must
@@ -493,7 +493,7 @@ def dot(self, other: Pauli, qargs: list | None = None, inplace: bool = False) ->
         """
         return self.compose(other, qargs=qargs, front=True, inplace=inplace)
 
-    def tensor(self, other: Pauli) -> Pauli:
+    def tensor(self, other) -> Pauli:
         if not isinstance(other, Pauli):
             other = Pauli(other)
         return Pauli(super().tensor(other))

qiskit/quantum_info/states/measures.py

@@ -214,9 +214,9 @@ def concurrence(state: Statevector | DensityMatrix) -> float:
     # If input is a density matrix it must be a 2-qubit state
     if state.dim != 4:
         raise QiskitError("Input density matrix must be a 2-qubit state.")
-    rho = DensityMatrix(state).data
+    rho_d = DensityMatrix(state).data
     yy_mat = np.fliplr(np.diag([-1, 1, 1, -1]))
-    sigma = rho.dot(yy_mat).dot(rho.conj()).dot(yy_mat)
+    sigma = rho_d.dot(yy_mat).dot(rho_d.conj()).dot(yy_mat)
     w = np.sort(np.real(la.eigvals(sigma)))
     w = np.sqrt(np.maximum(w, 0.0))
     return max(0.0, w[-1] - np.sum(w[0:-1]))

qiskit/quantum_info/states/quantum_state.py

@@ -48,7 +48,7 @@ def __init__(self, op_shape: OpShape | None = None):
     # Set higher priority than Numpy array and matrix classes
     __array_priority__ = 20
 
-    def __eq__(self, other) -> bool:
+    def __eq__(self, other: object) -> bool:
         return isinstance(other, self.__class__) and self.dims() == other.dims()
 
     @property