fix xgate in to_quirk (#1760)

xgate should be always X regardless of the value of `allow_global_phase`

Author: NoureldinYosri

qualtran/rotation_synthesis/channels/channel.py

@@ -308,10 +308,7 @@ def to_quirk(self, fmt: str = "xz", allow_global_phase: bool = True) -> str:
             raise ValueError(f"to_quirk is not supported for correction of type {type(correction)}")
         rot = ctr.to_quirk(self.rotation.to_matrix(), fmt, allow_global_phase)
         cor = ctr.to_quirk(correction.to_matrix(), fmt, allow_global_phase)
-        if allow_global_phase:
-            xgate = '"X"'
-        else:
-            xgate = '{"id":"Rzft","arg":"-pi"}'
+        xgate = '"X"'
         first_row = []
         second_row = []
         # CNOT

qualtran/rotation_synthesis/matrix/clifford_t_repr.py

@@ -61,12 +61,11 @@ def _xz_sequence(
     if use_hs:
         cliffords.append(su2_ct.HSqrt2)
         cliffords.append(su2_ct.HSqrt2 @ su2_ct.SSqrt2)
-    candidates = []
     pref = prv.removesuffix('*')
-    for name, t in _T_list:
-        if name.startswith(pref):
-            continue
-        for c in cliffords:
+    for c in cliffords:
+        for name, t in _T_list:
+            if name.startswith(pref):
+                continue
             new = c.adjoint() @ matrix
             new = t.adjoint() @ new
             new = new.scale_down()
@@ -76,11 +75,8 @@ def _xz_sequence(
             if seq is None:
                 continue
             gates = cast(tuple[str, ...], c.gates)
-            candidates.append(seq + (name,) + gates)
-            break
-    if not candidates:
-        return None
-    return min(candidates, key=len)
+            return seq + (name,) + gates
+    return None
 
 
 def to_sequence(matrix: su2_ct.SU2CliffordT, fmt: str = 'xyz') -> tuple[str, ...]: