Avoid implicitly converting 2-D arrays of single value to scalars

NumPy 2 raises deprecation warnings about converting an ndarray with
dimension > 0 of values likle `[[0]]` to a scalar value like `0`. The
solution is to get the value using `.item()`.

Author: mhucka

cirq-core/cirq/sim/simulator.py

@@ -912,7 +912,7 @@ def __repr__(self) -> str:
     def __str__(self) -> str:
         def bitstring(vals):
             separator = ' ' if np.max(vals) >= 10 else ''
-            return separator.join(str(int(v)) for v in vals)
+            return separator.join(str(int(v.item())) for v in vals)
 
         results = sorted([(key, bitstring(val)) for key, val in self.measurements.items()])
         if not results:

examples/bb84.py

@@ -128,7 +128,7 @@ def main(num_qubits=8):
     repetitions = 1
 
     result = cirq.Simulator().run(program=circuit, repetitions=repetitions)
-    result_bitstring = bitstring([int(result.measurements[str(q)]) for q in qubits])
+    result_bitstring = bitstring([int(result.measurements[str(q)][0].item()) for q in qubits])
 
     # Take only qubits where bases match
     obtained_key = ''.join(
@@ -158,14 +158,14 @@ def main(num_qubits=8):
     # Run simulations.
     repetitions = 1
     result = cirq.Simulator().run(program=alice_eve_circuit, repetitions=repetitions)
-    eve_state = [int(result.measurements[str(q)]) for q in qubits]
+    eve_state = [int(result.measurements[str(q)][0].item()) for q in qubits]
 
     eve_bob_circuit = make_bb84_circ(num_qubits, eve_basis, bob_basis, eve_state)
 
     # Run simulations.
     repetitions = 1
     result = cirq.Simulator().run(program=eve_bob_circuit, repetitions=repetitions)
-    result_bitstring = bitstring([int(result.measurements[str(q)]) for q in qubits])
+    result_bitstring = bitstring([int(result.measurements[str(q)][0].item()) for q in qubits])
 
     # Take only qubits where bases match
     obtained_key = ''.join(