fix cswap definition bug (#685)

* fix cswap definition bug

* add to changelog

CHANGELOG.rst

@@ -38,6 +38,7 @@ Removed
 Fixed
 -----
 - Fixed ``probabilities_ket`` computation in C++ simulator. (#580)
+- Fixed bug in the definition of ``cswap`` gate and its test (#685).
 - Fixed the examples to be compatible with version 0.5+ (#672)
 
 

qiskit/extensions/standard/cswap.py

@@ -21,7 +21,7 @@ class FredkinGate(Gate):
 
     def __init__(self, ctl, tgt1, tgt2, circ=None):
         """Create new Fredkin gate."""
-        super().__init__("ccx", [], [ctl, tgt1, tgt2], circ)
+        super().__init__("cswap", [], [ctl, tgt1, tgt2], circ)
 
     def qasm(self):
         """Return OPENQASM string."""

test/python/test_extensions_standard.py

@@ -169,7 +169,7 @@ def test_crz_invalid(self):
 
     def test_cswap(self):
         self.circuit.cswap(self.q[0], self.q[1], self.q[2])
-        qasm_txt = 'cx q[2],q[1];\nccx q[0],q[1],q[2];\ncx q[2],q[1];'
+        qasm_txt = 'cswap q[0],q[1],q[2];'
         self.assertResult(FredkinGate, qasm_txt, qasm_txt)
 
     def test_cswap_invalid(self):
@@ -733,19 +733,6 @@ def test_rzz(self):
         c.rzz(pi/2, self.q[1], self.q[2])
         self.assertResult(RZZGate, 'rzz(pi/2) q[1],q[2];', 'rzz(-pi/2) q[1],q[2];')
 
-    def assertResult(self, t, qasm_txt, qasm_txt_):
-        """
-        t: type
-        qasm_txt: qasm representation
-        qasm_txt_: qasm representation of inverse
-        """
-        c = self.circuit
-        self.assertRaises(QISKitError, c.z, self.c[0])
-        self.assertRaises(QISKitError, c.z, self.c)
-        self.assertRaises(QISKitError, c.z, (self.q, 3))
-        self.assertRaises(QISKitError, c.z, (self.q, 'a'))
-        self.assertRaises(QISKitError, c.z, 0)
-
     def test_z_reg(self):
         qasm_txt = 'z q[0];\nz q[1];\nz q[2];'
         instruction_set = self.circuit.z(self.q)