From a2078319046db6a2b702ca18579ff9a12102207a Mon Sep 17 00:00:00 2001
From: Douglas Wilson <douglas.wilson@quantinuum.com>
Date: Tue, 22 Aug 2023 08:46:10 +0100
Subject: [PATCH 1/2] TKET-3469 Allow setting of RNG seed

---
 docs/changelog.rst                            |  5 +++
 .../qulacs/backends/qulacs_backend.py         | 18 +++++++++--
 tests/test_qulacs_backend.py                  | 31 +++++++++++++++++--
 3 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index c857a39..3a84aa2 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,6 +1,11 @@
 Changelog
 ~~~~~~~~~
 
+0.30.0 (August 2023)
+--------------------
+
+* Allow setting of rng seed in qulacs backend.
+
 0.29.0 (June 2023)
 ------------------
 
diff --git a/pytket/extensions/qulacs/backends/qulacs_backend.py b/pytket/extensions/qulacs/backends/qulacs_backend.py
index 859383e..552af9b 100644
--- a/pytket/extensions/qulacs/backends/qulacs_backend.py
+++ b/pytket/extensions/qulacs/backends/qulacs_backend.py
@@ -15,8 +15,9 @@
 """Methods to allow tket circuits to be ran on the Qulacs simulator
 """
 
-from typing import List, Optional, Sequence, Union
+from typing import List, Optional, Sequence, Union, cast
 from logging import warning
+from random import Random
 from uuid import uuid4
 import numpy as np
 from sympy import Expr  # type: ignore
@@ -181,6 +182,9 @@ def process_circuits(
         if valid_check:
             self._check_all_circuits(circuits, nomeasure_warn=False)
 
+        seed = cast(Optional[int], kwargs.get("seed"))
+        rng = Random(seed) if seed else None
+
         handle_list = []
         for circuit, n_shots_circ in zip(circuits, n_shots_list):
             qulacs_state = self._sim(circuit.n_qubits)
@@ -205,7 +209,9 @@ def process_circuits(
                 else:
                     bits, choose_indices = zip(*bits2index)
 
-                    samples = qulacs_state.sampling(n_shots_circ)
+                    samples = self._sample_quantum_state(
+                        qulacs_state, n_shots_circ, rng
+                    )
                     shots = OutcomeArray.from_ints(samples, circuit.n_qubits)
                     shots = shots.choose_indices(choose_indices)
             try:
@@ -228,6 +234,14 @@ def process_circuits(
             del qulacs_circ
         return handle_list
 
+    def _sample_quantum_state(
+        self, quantum_state: QuantumState, n_shots: int, rng: Optional[Random]
+    ) -> List[int]:
+        if rng:
+            return quantum_state.sampling(n_shots, rng.randint(0, 2**32 - 1))
+        else:
+            return quantum_state.sampling(n_shots)
+
     def circuit_status(self, handle: ResultHandle) -> CircuitStatus:
         if handle in self._cache:
             return CircuitStatus(StatusEnum.COMPLETED)
diff --git a/tests/test_qulacs_backend.py b/tests/test_qulacs_backend.py
index 8e251ff..2244bb2 100644
--- a/tests/test_qulacs_backend.py
+++ b/tests/test_qulacs_backend.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from collections import Counter
+from typing import List, Sequence, Union, Optional
 import warnings
 import math
 from hypothesis import given, strategies
@@ -20,18 +21,43 @@
 import pytest
 from openfermion.ops import QubitOperator  # type: ignore
 from openfermion.linalg import eigenspectrum  # type: ignore
+from pytket.backends import ResultHandle
 from pytket.circuit import Circuit, BasisOrder, OpType, Qubit  # type: ignore
 from pytket.pauli import Pauli, QubitPauliString  # type: ignore
 from pytket.passes import CliffordSimp  # type: ignore
 from pytket.utils.operators import QubitPauliOperator
+from pytket.utils.results import KwargTypes
 from pytket.extensions.qulacs import QulacsBackend
 
-backends = [QulacsBackend()]
+
+def make_seeded_QulacsBackend(base: type[QulacsBackend]) -> type:
+    class SeededQulacsBackend(base):  # type: ignore
+        def __init__(self, seed: int):
+            base.__init__(self)
+            self._seed = seed
+
+        def process_circuits(
+            self,
+            circuits: Sequence[Circuit],
+            n_shots: Union[None, int, Sequence[Optional[int]]] = None,
+            valid_check: bool = True,
+            **kwargs: KwargTypes
+        ) -> List[ResultHandle]:
+            if not "seed" in kwargs:
+                kwargs["seed"] = self._seed
+            return base.process_circuits(self, circuits, n_shots, valid_check, **kwargs)
+
+    return SeededQulacsBackend
+
+
+backends = [QulacsBackend(), make_seeded_QulacsBackend(QulacsBackend)(-1)]
 
 try:
     from pytket.extensions.qulacs import QulacsGPUBackend
 
-    backends.append(QulacsGPUBackend())
+    backends.extend(
+        [QulacsGPUBackend(), make_seeded_QulacsBackend(QulacsGPUBackend)(1)]
+    )
 except ImportError:
     warnings.warn("local settings failed to import QulacsGPUBackend", ImportWarning)
 
@@ -266,7 +292,6 @@ def test_shots_bits_edgecases(n_shots, n_bits) -> None:
     c = Circuit(n_bits, n_bits)
 
     for qulacs_backend in backends:
-
         # TODO TKET-813 add more shot based backends and move to integration tests
         h = qulacs_backend.process_circuit(c, n_shots)
         res = qulacs_backend.get_result(h)

From 1622df2cb2c717a2b0be56bdc3ae429d8f7fe842 Mon Sep 17 00:00:00 2001
From: doug-q <141026920+doug-q@users.noreply.github.com>
Date: Tue, 22 Aug 2023 16:14:39 +0100
Subject: [PATCH 2/2] Update docs/changelog.rst

Co-authored-by: yao-cqc <75305462+yao-cqc@users.noreply.github.com>
---
 docs/changelog.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 3a84aa2..bc2378f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,7 +1,7 @@
 Changelog
 ~~~~~~~~~
 
-0.30.0 (August 2023)
+Unreleased
 --------------------
 
 * Allow setting of rng seed in qulacs backend.