Uncompute (bug/feature)

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v0.3.1 (2024-02-25)
+
+Bug fix / feature addition: "uncompute" after observable calculation (to allow different bases of observation for the same qubits).
+
 ## v0.3.0 (2024-02-25)
 
 Features added:

src/braket/qrack_simulator/_version.py

@@ -1 +1 @@
-0.3.0
+0.3.1

src/braket/qrack_simulator/qrack_simulator.py

@@ -191,8 +191,12 @@ def run(self, ir: OQ3Program, shots=1, is_reactively_separated=False, sdrp=-1, n
                         obs = Observable.H()
                     else:
                         raise ValueError("BraketQrackSimulator only allows x, y, z, i, and h basis sample, variance, and expectation return values!")
+
+                    # "Compute" must "uncompute" to restore original state (for outer loop).
+                    # We "compute" by `basis_rotation_gates`, then we uncompute later.
                     for g in obs.basis_rotation_gates:
                         qsim.mtrx(g.to_matrix().flatten().tolist(), b[0])
+
                     if tensor_product is None:
                         tensor_product = obs
                     else:
@@ -233,6 +237,12 @@ def run(self, ir: OQ3Program, shots=1, is_reactively_separated=False, sdrp=-1, n
                     else:
                         resultTypes.append(jaqcd.Expectation.construct(observable=tensor_product.to_ir(), targets=qubits))
 
+                for b in qubit_bases:
+                    # "Compute" must "uncompute" to restore original state (for outer loop).
+                    # We "uncompute" by reversed gate order and conjugate transposition of elements with getH().
+                    for g in reversed(obs.basis_rotation_gates):
+                        qsim.mtrx(g.getH().to_matrix().flatten().tolist(), b[0])
+
         return GateModelTaskResult.construct(
             taskMetadata=TaskMetadata(
                 id=str(uuid.uuid4()),