From c4d42ec086c6d501edf30d8e31880af41c4867ec Mon Sep 17 00:00:00 2001
From: Josh Izaac <josh146@gmail.com>
Date: Fri, 16 Apr 2021 20:41:41 +0800
Subject: [PATCH 1/4] Fixes bug where repeated Torch interface after expansion
 caused an error

---
 pennylane/tape/tape.py              |  1 +
 tests/interfaces/test_tape_torch.py | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/pennylane/tape/tape.py b/pennylane/tape/tape.py
index 60764fcf6d7..674575d1b0c 100644
--- a/pennylane/tape/tape.py
+++ b/pennylane/tape/tape.py
@@ -153,6 +153,7 @@ def expand_tape(tape, depth=1, stop_at=None, expand_measurements=False):
         stop_at = lambda obj: False
 
     new_tape = tape.__class__()
+    new_tape.__bare__ = getattr(tape, "__bare__", tape.__class__)
 
     # Check for observables acting on the same wire. If present, observables must be
     # qubit-wise commuting Pauli words. In this case, the tape is expanded with joint
diff --git a/tests/interfaces/test_tape_torch.py b/tests/interfaces/test_tape_torch.py
index 144104e1d78..8e9963d1876 100644
--- a/tests/interfaces/test_tape_torch.py
+++ b/tests/interfaces/test_tape_torch.py
@@ -453,3 +453,24 @@ def test_complex_min_version(self, monkeypatch):
             m.setattr(qml.interfaces.torch, "COMPLEX_SUPPORT", False)
             with pytest.raises(qml.QuantumFunctionError, match=r"Version 1\.6\.0 or above of PyTorch"):
                 TorchInterface.apply(JacobianTape(), dtype=torch.complex128)
+
+    def test_repeated_application_after_expand(self, tol):
+        """Test that the Torch interface continues to work after
+        tape expansions, and repeated torch application"""
+        n_qubits = 2
+        dev = qml.device("default.qubit", wires=n_qubits)
+
+        weights = torch.ones((3,))
+
+        with TorchInterface.apply(qml.tape.QuantumTape()) as tape:
+            qml.U3(*weights, wires=0)
+            qml.expval(qml.PauliZ(wires=0))
+
+        tape = tape.expand()
+
+        res1 = tape.execute(dev)
+
+        TorchInterface.apply(tape)
+        res2 = tape.execute(dev)
+
+        assert np.allclose(res1, res2, atol=tol, rtol=0)

From 1b480180a3253ae136f37fde5cc8b15a0c04fccc Mon Sep 17 00:00:00 2001
From: Josh Izaac <josh146@gmail.com>
Date: Fri, 16 Apr 2021 20:42:24 +0800
Subject: [PATCH 2/4] update changelog

---
 .github/CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
index 49086b34e1f..918ee7eb296 100644
--- a/.github/CHANGELOG.md
+++ b/.github/CHANGELOG.md
@@ -770,6 +770,9 @@
   second-order observable.
   [(#1197)](https://github.com/PennyLaneAI/pennylane/pull/1197)
 
+* Fixes a bug where repeated Torch interface after expansion caused an error.
+  [(#)](https://github.com/PennyLaneAI/pennylane/pull/)
+
 <h3>Documentation</h3>
 
 - Typos addressed in templates documentation.

From 3613fd50805a8dd68f702467b3403954c9060a3e Mon Sep 17 00:00:00 2001
From: Josh Izaac <josh146@gmail.com>
Date: Fri, 16 Apr 2021 20:48:33 +0800
Subject: [PATCH 3/4] Update .github/CHANGELOG.md

---
 .github/CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
index 918ee7eb296..1addc2d3a52 100644
--- a/.github/CHANGELOG.md
+++ b/.github/CHANGELOG.md
@@ -771,7 +771,7 @@
   [(#1197)](https://github.com/PennyLaneAI/pennylane/pull/1197)
 
 * Fixes a bug where repeated Torch interface after expansion caused an error.
-  [(#)](https://github.com/PennyLaneAI/pennylane/pull/)
+  [(#1223)](https://github.com/PennyLaneAI/pennylane/pull/1223)
 
 <h3>Documentation</h3>
 

From b828b2ebec5bbc80c0e0841b1a227a25bd2b771b Mon Sep 17 00:00:00 2001
From: Josh Izaac <josh146@gmail.com>
Date: Fri, 16 Apr 2021 22:24:43 +0800
Subject: [PATCH 4/4] Update .github/CHANGELOG.md

Co-authored-by: Tom Bromley <49409390+trbromley@users.noreply.github.com>
---
 .github/CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
index 1addc2d3a52..c5ab0bf1f94 100644
--- a/.github/CHANGELOG.md
+++ b/.github/CHANGELOG.md
@@ -770,7 +770,7 @@
   second-order observable.
   [(#1197)](https://github.com/PennyLaneAI/pennylane/pull/1197)
 
-* Fixes a bug where repeated Torch interface after expansion caused an error.
+* Fixes a bug where repeated Torch interface applications after expansion caused an error.
   [(#1223)](https://github.com/PennyLaneAI/pennylane/pull/1223)
 
 <h3>Documentation</h3>