Add internal evolve methods by Clifford gates (#15813)

* add _evolve_sx, _evolve_sxdg, _evolve_dcx, _evolve_iswap

* add tests for _append_circuit method

* rewrite _evolve_dcx

* rewrite _evolve_iswap

* simplify _evolve_iswap phase calc

* update test

* unify tests

* enhance test of a random clifford circuit to include qargs

* enhance test for a random clifford circuit to include h method

* test only evolve and not internal methods

* simlify tests

Author: ShellyGarion

qiskit/quantum_info/operators/symplectic/base_pauli.py

@@ -636,6 +636,22 @@ def _evolve_sdg(base_pauli, qubit):
     return base_pauli
 
 
+def _evolve_sx(base_pauli, qubit):
+    """Update P -> SX.P.SXdg"""
+    z = base_pauli._z[:, qubit]
+    base_pauli._x[:, qubit] ^= z
+    base_pauli._phase -= z.T.astype(base_pauli._phase.dtype)
+    return base_pauli
+
+
+def _evolve_sxdg(base_pauli, qubit):
+    """Update P -> SXdg.P.SX"""
+    z = base_pauli._z[:, qubit]
+    base_pauli._x[:, qubit] ^= z
+    base_pauli._phase += z.T.astype(base_pauli._phase.dtype)
+    return base_pauli
+
+
 def _evolve_i(base_pauli, qubit):
     """Update P -> P"""
     return base_pauli
@@ -690,6 +706,15 @@ def _evolve_cy(base_pauli, qctrl, qtrgt):
     return base_pauli
 
 
+def _evolve_dcx(base_pauli, qctrl, qtrgt):
+    """Update P -> DCX.P.DCXdg"""
+    base_pauli._x[:, qtrgt] ^= base_pauli._x[:, qctrl]
+    base_pauli._z[:, qctrl] ^= base_pauli._z[:, qtrgt]
+    base_pauli._x[:, qctrl] ^= base_pauli._x[:, qtrgt]
+    base_pauli._z[:, qtrgt] ^= base_pauli._z[:, qctrl]
+    return base_pauli
+
+
 def _evolve_swap(base_pauli, q1, q2):
     """Update P -> SWAP.P.SWAP"""
     x1 = base_pauli._x[:, q1].copy()
@@ -701,6 +726,22 @@ def _evolve_swap(base_pauli, q1, q2):
     return base_pauli
 
 
+def _evolve_iswap(base_pauli, q1, q2):
+    """Update P -> iSWAP.P.iSWAP"""
+    x1 = base_pauli._x[:, q1].copy()
+    z1 = base_pauli._z[:, q1].copy()
+    x2 = base_pauli._x[:, q2].copy()
+    z2 = base_pauli._z[:, q2].copy()
+
+    base_pauli._x[:, q1] = x2
+    base_pauli._x[:, q2] = x1
+    base_pauli._z[:, q1] = x1 ^ x2 ^ z2
+    base_pauli._z[:, q2] = x1 ^ x2 ^ z1
+
+    base_pauli._phase += np.logical_xor(x1, x2).T.astype(base_pauli._phase.dtype)
+    return base_pauli
+
+
 def _evolve_ecr(base_pauli, q1, q2):
     """Update P -> ECR.P.ECR"""
     base_pauli = _evolve_s(base_pauli, q1)
@@ -740,13 +781,17 @@ def _count_y(x, z, dtype=None):
     "s": _evolve_s,
     "sdg": _evolve_sdg,
     "sinv": _evolve_sdg,
+    "sx": _evolve_sx,
+    "sxdg": _evolve_sxdg,
 }
 _basis_2q = {
     "cx": _evolve_cx,
     "cz": _evolve_cz,
     "cy": _evolve_cy,
     "swap": _evolve_swap,
+    "iswap": _evolve_iswap,
     "ecr": _evolve_ecr,
+    "dcx": _evolve_dcx,
 }
 
 # Non-Clifford gates

test/python/quantum_info/operators/symplectic/test_pauli.py

@@ -24,6 +24,7 @@
 
 from qiskit import QuantumCircuit
 from qiskit.circuit import Qubit
+from qiskit.circuit.random import random_clifford_circuit
 from qiskit.circuit.library import (
     CXGate,
     CYGate,
@@ -36,6 +37,7 @@
     SGate,
     SwapGate,
     iSwapGate,
+    DCXGate,
     XGate,
     YGate,
     ZGate,
@@ -449,6 +451,7 @@ def test_evolve_clifford1(self, gate, label):
                 SwapGate(),
                 iSwapGate(),
                 ECRGate(),
+                DCXGate(),
                 CPhaseGate(theta=np.pi),
                 CRXGate(theta=np.pi),
                 CRYGate(theta=np.pi),
@@ -489,11 +492,15 @@ def test_evolve_clifford2(self, gate, label):
                 HGate(),
                 SGate(),
                 SdgGate(),
+                SXGate(),
+                SXdgGate(),
                 CXGate(),
                 CYGate(),
                 CZGate(),
                 SwapGate(),
+                iSwapGate(),
                 ECRGate(),
+                DCXGate(),
             ),
             [int, np.int8, np.uint8, np.int16, np.uint16, np.int32, np.uint32, np.int64, np.uint64],
         )
@@ -523,6 +530,19 @@ def test_evolve_clifford_qargs(self):
         self.assertEqual(value, value_h)
         self.assertEqual(value_inv, value_s)
 
+    def test_evolve_clifford_circuit_qargs(self):
+        """Test evolve method for random Clifford circuit"""
+        qargs = [2, 4, 1, 0]
+        qc = random_clifford_circuit(4, 100, seed=123)
+        op = Operator(qc)
+        pauli = random_pauli(5, seed=5678)
+        target_s = Operator(pauli).compose(op, qargs=qargs).dot(op.adjoint(), qargs=qargs)
+        target_h = Operator(pauli).compose(op.adjoint(), qargs=qargs).dot(op, qargs=qargs)
+        value_evolve_s = Operator(pauli.evolve(qc, frame="s", qargs=qargs))
+        value_evolve_h = Operator(pauli.evolve(qc, frame="h", qargs=qargs))
+        self.assertEqual(value_evolve_s, target_s)
+        self.assertEqual(value_evolve_h, target_h)
+
     @data("s", "h")
     def test_evolve_with_misleading_name(self, frame):
         """Test evolve by circuit contents, not by name (fixed bug)."""