From 6ff471a42c3b6baf1a7d32cfa986d189aace257f Mon Sep 17 00:00:00 2001
From: Caleb Johnson <calebj1524@outlook.com>
Date: Wed, 21 Jun 2023 15:21:21 -0500
Subject: [PATCH] Add a supported_gates function (#277)

* Add a supported_gates function

* use sets instead of tuples

* Fix docstring

* Add release note

* Fix test

* Update circuit_knitting/cutting/qpd/qpd.py

Co-authored-by: Jim Garrison <garrison@ibm.com>

* Add new function to package and sphinx docs

---------

Co-authored-by: Jim Garrison <garrison@ibm.com>
---
 circuit_knitting/cutting/__init__.py                   |  1 +
 circuit_knitting/cutting/qpd/__init__.py               |  2 ++
 circuit_knitting/cutting/qpd/qpd.py                    | 10 ++++++++++
 .../notes/supported-gates-d2156f58bc07fc7a.yaml        |  4 ++++
 test/cutting/qpd/test_qpd.py                           |  4 ++++
 5 files changed, 21 insertions(+)
 create mode 100644 releasenotes/notes/supported-gates-d2156f58bc07fc7a.yaml

diff --git a/circuit_knitting/cutting/__init__.py b/circuit_knitting/cutting/__init__.py
index 1e75ce5f2..14ebc6d7a 100644
--- a/circuit_knitting/cutting/__init__.py
+++ b/circuit_knitting/cutting/__init__.py
@@ -57,6 +57,7 @@
 
     qpd.generate_qpd_samples
     qpd.decompose_qpd_instructions
+    qpd.supported_gates
 
 CutQC
 =====
diff --git a/circuit_knitting/cutting/qpd/__init__.py b/circuit_knitting/cutting/qpd/__init__.py
index 8e0f36960..646abc03a 100644
--- a/circuit_knitting/cutting/qpd/__init__.py
+++ b/circuit_knitting/cutting/qpd/__init__.py
@@ -17,6 +17,7 @@
     decompose_qpd_instructions,
     WeightType,
     qpdbasis_from_gate,
+    supported_gates,
 )
 from .instructions import (
     BaseQPDGate,
@@ -29,6 +30,7 @@
     "qpdbasis_from_gate",
     "generate_qpd_samples",
     "decompose_qpd_instructions",
+    "supported_gates",
     "QPDBasis",
     "BaseQPDGate",
     "TwoQubitQPDGate",
diff --git a/circuit_knitting/cutting/qpd/qpd.py b/circuit_knitting/cutting/qpd/qpd.py
index d66040937..995f5d781 100644
--- a/circuit_knitting/cutting/qpd/qpd.py
+++ b/circuit_knitting/cutting/qpd/qpd.py
@@ -215,6 +215,16 @@ def qpdbasis_from_gate(gate: Gate) -> QPDBasis:
         return f(gate)
 
 
+def supported_gates() -> set[str]:
+    """
+    Return a set of gate names supported for automatic decomposition.
+
+    Returns:
+        Set of gate names supported for automatic decomposition.
+    """
+    return set(_qpdbasis_from_gate_funcs)
+
+
 @_register_qpdbasis_from_gate("rxx", "ryy", "rzz", "crx", "cry", "crz")
 def _(gate: RXXGate | RYYGate | RZZGate | CRXGate | CRYGate | CRZGate):
     # Constructing a virtual two-qubit gate by sampling single-qubit operations - Mitarai et al
diff --git a/releasenotes/notes/supported-gates-d2156f58bc07fc7a.yaml b/releasenotes/notes/supported-gates-d2156f58bc07fc7a.yaml
new file mode 100644
index 000000000..dcb6ba4d5
--- /dev/null
+++ b/releasenotes/notes/supported-gates-d2156f58bc07fc7a.yaml
@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    Addition of :func:`~circuit_knitting.cutting.qpd.supported_gates` function, which returns the names of all gates which may be automatically decomposed using :func:`~circuit_knitting.cutting.qpd.qpdbasis_from_gate`.
diff --git a/test/cutting/qpd/test_qpd.py b/test/cutting/qpd/test_qpd.py
index 12b77d98b..56f4fc555 100644
--- a/test/cutting/qpd/test_qpd.py
+++ b/test/cutting/qpd/test_qpd.py
@@ -279,3 +279,7 @@ def test_qpdbasis_from_gate_unique_maps(
         ]
         assert len(unique_by_eq(a for (a, b) in relevant_maps)) == q0_num_unique
         assert len(unique_by_eq(b for (a, b) in relevant_maps)) == q1_num_unique
+
+    def test_supported_gates(self):
+        gates = supported_gates()
+        self.assertEqual({"rxx", "ryy", "rzz", "crx", "cry", "crz", "cx", "cz"}, gates)