From cf0017a3ebd3a6e6f48b59b8dc8aa5a3b637b29e Mon Sep 17 00:00:00 2001
From: Jim Garrison <garrison@ibm.com>
Date: Fri, 30 Jun 2023 15:14:17 -0400
Subject: [PATCH] `CSXGate` (#296)

* sxgate

* Add t rotation

* Tests pass

* Black

---------

Co-authored-by: Caleb Johnson <calebj1524@outlook.com>
---
 circuit_knitting/cutting/qpd/qpd.py    | 10 ++++++++++
 test/cutting/qpd/test_qpd.py           |  3 ++-
 test/cutting/test_cutting_roundtrip.py |  2 ++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/circuit_knitting/cutting/qpd/qpd.py b/circuit_knitting/cutting/qpd/qpd.py
index 6771798c0..9f3d34d01 100644
--- a/circuit_knitting/cutting/qpd/qpd.py
+++ b/circuit_knitting/cutting/qpd/qpd.py
@@ -32,6 +32,7 @@
     ZGate,
     HGate,
     SGate,
+    TGate,
     SdgGate,
     RXGate,
     RYGate,
@@ -46,6 +47,7 @@
     CRXGate,
     CRYGate,
     CRZGate,
+    CSXGate,
 )
 
 from .qpd_basis import QPDBasis
@@ -308,6 +310,14 @@ def _(gate: RXXGate | RYYGate | RZZGate | CRXGate | CRYGate | CRZGate):
     return QPDBasis(maps, coeffs)
 
 
+@_register_qpdbasis_from_gate("csx")
+def _(gate: CSXGate):
+    retval = qpdbasis_from_gate(CRXGate(np.pi / 2))
+    for operations in unique_by_id(m[0] for m in retval.maps):
+        operations.insert(0, TGate())
+    return retval
+
+
 @_register_qpdbasis_from_gate("cx", "cy", "cz", "ch")
 def _(gate: CXGate | CYGate | CZGate | CHGate):
     # Constructing a virtual two-qubit gate by sampling single-qubit operations - Mitarai et al
diff --git a/test/cutting/qpd/test_qpd.py b/test/cutting/qpd/test_qpd.py
index 144b2849d..bed100af5 100644
--- a/test/cutting/qpd/test_qpd.py
+++ b/test/cutting/qpd/test_qpd.py
@@ -283,5 +283,6 @@ def test_qpdbasis_from_gate_unique_maps(
     def test_supported_gates(self):
         gates = supported_gates()
         self.assertEqual(
-            {"rxx", "ryy", "rzz", "crx", "cry", "crz", "cx", "cy", "cz", "ch"}, gates
+            {"rxx", "ryy", "rzz", "crx", "cry", "crz", "cx", "cy", "cz", "ch", "csx"},
+            gates,
         )
diff --git a/test/cutting/test_cutting_roundtrip.py b/test/cutting/test_cutting_roundtrip.py
index be36cbacd..9ce5ecbc7 100644
--- a/test/cutting/test_cutting_roundtrip.py
+++ b/test/cutting/test_cutting_roundtrip.py
@@ -28,6 +28,7 @@
     CRXGate,
     CRYGate,
     CRZGate,
+    CSXGate,
 )
 from qiskit.extensions import UnitaryGate
 from qiskit.quantum_info import PauliList, random_unitary
@@ -54,6 +55,7 @@ def append_random_unitary(circuit: QuantumCircuit, qubits):
         [CYGate()],
         [CZGate()],
         [CHGate()],
+        [CSXGate()],
         [RYYGate(0.0)],
         [RZZGate(np.pi)],
         [RXXGate(np.pi / 3)],