Deprecate ignore_measurement_results (quantumlib#4978)

This can now be done in the measurement transformers, which also handle classically controlled operations. The simulator option does not (and can not) handle classical controls. This no longer should be a simulator option.

Fixes quantumlib#4975

Author: daxfohl

cirq/sim/act_on_args.py

@@ -33,7 +33,7 @@
 import numpy as np
 
 from cirq import ops, protocols, value
-from cirq._compat import deprecated
+from cirq._compat import deprecated, deprecated_parameter
 from cirq.protocols.decompose_protocol import _try_decompose_into_operations_and_qubits
 from cirq.sim.operation_target import OperationTarget
 
@@ -46,6 +46,12 @@
 class ActOnArgs(OperationTarget[TSelf]):
     """State and context for an operation acting on a state tensor."""
 
+    @deprecated_parameter(
+        deadline='v0.15',
+        fix='Use cirq.dephase_measurements to transform the circuit before simulating.',
+        parameter_desc='ignore_measurement_results',
+        match=lambda args, kwargs: 'ignore_measurement_results' in kwargs or len(args) > 4,
+    )
     def __init__(
         self,
         prng: Optional[np.random.RandomState] = None,

cirq/sim/act_on_density_matrix_args.py

@@ -33,6 +33,12 @@ class ActOnDensityMatrixArgs(ActOnArgs):
     storing the density matrix of the quantum system with one axis per qubit.
     """
 
+    @_compat.deprecated_parameter(
+        deadline='v0.15',
+        fix='Use cirq.dephase_measurements to transform the circuit before simulating.',
+        parameter_desc='ignore_measurement_results',
+        match=lambda args, kwargs: 'ignore_measurement_results' in kwargs or len(args) > 7,
+    )
     @_compat.deprecated_parameter(
         deadline='v0.15',
         fix='Use initial_state instead and specify all the arguments with keywords.',
@@ -86,13 +92,21 @@ def __init__(
             ValueError: The dimension of `target_tensor` is not divisible by 2
                 and `qid_shape` is not provided.
         """
-        super().__init__(
-            prng=prng,
-            qubits=qubits,
-            log_of_measurement_results=log_of_measurement_results,
-            ignore_measurement_results=ignore_measurement_results,
-            classical_data=classical_data,
-        )
+        if ignore_measurement_results:
+            super().__init__(
+                prng=prng,
+                qubits=qubits,
+                log_of_measurement_results=log_of_measurement_results,
+                ignore_measurement_results=ignore_measurement_results,
+                classical_data=classical_data,
+            )
+        else:
+            super().__init__(
+                prng=prng,
+                qubits=qubits,
+                log_of_measurement_results=log_of_measurement_results,
+                classical_data=classical_data,
+            )
         if target_tensor is None:
             qubits_qid_shape = protocols.qid_shape(self.qubits)
             initial_matrix = qis.to_valid_density_matrix(

cirq/sim/density_matrix_simulator.py

@@ -17,7 +17,7 @@
 import numpy as np
 
 from cirq import ops, protocols, study, value
-from cirq._compat import deprecated, proper_repr
+from cirq._compat import deprecated, deprecated_parameter, proper_repr
 from cirq.sim import (
     simulator,
     act_on_density_matrix_args,
@@ -117,6 +117,12 @@ class DensityMatrixSimulator(
            # step_result.density_matrix()
     """
 
+    @deprecated_parameter(
+        deadline='v0.15',
+        fix='Use cirq.dephase_measurements to transform the circuit before simulating.',
+        parameter_desc='ignore_measurement_results',
+        match=lambda _, kwargs: 'ignore_measurement_results' in kwargs,
+    )
     def __init__(
         self,
         *,
@@ -162,13 +168,21 @@ def __init__(
            when `ignore_measurement_results` has been set to True
            (for more see https://github.com/quantumlib/Cirq/issues/2777).
         """
-        super().__init__(
-            dtype=dtype,
-            noise=noise,
-            seed=seed,
-            ignore_measurement_results=ignore_measurement_results,
-            split_untangled_states=split_untangled_states,
-        )
+        if ignore_measurement_results:
+            super().__init__(
+                dtype=dtype,
+                noise=noise,
+                seed=seed,
+                ignore_measurement_results=ignore_measurement_results,
+                split_untangled_states=split_untangled_states,
+            )
+        else:
+            super().__init__(
+                dtype=dtype,
+                noise=noise,
+                seed=seed,
+                split_untangled_states=split_untangled_states,
+            )
         if dtype not in {np.complex64, np.complex128}:
             raise ValueError(f'dtype must be complex64 or complex128, was {dtype}')
 
@@ -195,11 +209,19 @@ def _create_partial_act_on_args(
         if isinstance(initial_state, act_on_density_matrix_args.ActOnDensityMatrixArgs):
             return initial_state
 
+        if self._ignore_measurement_results:
+            return act_on_density_matrix_args.ActOnDensityMatrixArgs(
+                qubits=qubits,
+                prng=self._prng,
+                classical_data=classical_data,
+                ignore_measurement_results=self._ignore_measurement_results,
+                initial_state=initial_state,
+                dtype=self._dtype,
+            )
         return act_on_density_matrix_args.ActOnDensityMatrixArgs(
             qubits=qubits,
             prng=self._prng,
             classical_data=classical_data,
-            ignore_measurement_results=self._ignore_measurement_results,
             initial_state=initial_state,
             dtype=self._dtype,
         )

cirq/sim/density_matrix_simulator_test.py

@@ -73,9 +73,10 @@ def test_invalid_dtype():
 @pytest.mark.parametrize('split', [True, False])
 def test_run_with_ignore_measurement_results(dtype: Type[np.number], split: bool):
     q0, q1 = cirq.LineQubit.range(2)
-    simulator = cirq.DensityMatrixSimulator(
-        dtype=dtype, ignore_measurement_results=True, split_untangled_states=split
-    )
+    with cirq.testing.assert_deprecated('ignore_measurement_results', deadline='v0.15', count=2):
+        simulator = cirq.DensityMatrixSimulator(
+            dtype=dtype, ignore_measurement_results=True, split_untangled_states=split
+        )
 
     circuit = cirq.Circuit(cirq.X(q0), cirq.X(q1), cirq.measure(q0))
     with pytest.raises(ValueError, match="ignore_measurement_results = True"):
@@ -517,26 +518,32 @@ def test_simulate(dtype: Type[np.number], split: bool):
 @pytest.mark.parametrize('split', [True, False])
 def test_simulate_ignore_measurements(split: bool):
     q0 = cirq.LineQubit(0)
-    simulator = cirq.DensityMatrixSimulator(
-        split_untangled_states=split, ignore_measurement_results=True
-    )
-    circuit = cirq.Circuit(cirq.H(q0), cirq.measure(q0))
-    result = simulator.simulate(circuit)
-    np.testing.assert_almost_equal(result.final_density_matrix, np.eye(2) * 0.5)
-    assert len(result.measurements) == 0
+    with cirq.testing.assert_deprecated(
+        'ignore_measurement_results', deadline='v0.15', count=6 if split else 4
+    ):
+        simulator = cirq.DensityMatrixSimulator(
+            split_untangled_states=split, ignore_measurement_results=True
+        )
+        circuit = cirq.Circuit(cirq.H(q0), cirq.measure(q0))
+        result = simulator.simulate(circuit)
+        np.testing.assert_almost_equal(result.final_density_matrix, np.eye(2) * 0.5)
+        assert len(result.measurements) == 0
 
 
 @pytest.mark.parametrize('split', [True, False])
 def test_simulate_ignore_measurements_subcircuits(split: bool):
     q0 = cirq.LineQubit(0)
-    simulator = cirq.DensityMatrixSimulator(
-        split_untangled_states=split, ignore_measurement_results=True
-    )
-    circuit = cirq.Circuit(cirq.H(q0), cirq.measure(q0))
-    circuit = cirq.Circuit(cirq.CircuitOperation(circuit.freeze()))
-    result = simulator.simulate(circuit)
-    np.testing.assert_almost_equal(result.final_density_matrix, np.eye(2) * 0.5)
-    assert len(result.measurements) == 0
+    with cirq.testing.assert_deprecated(
+        'ignore_measurement_results', deadline='v0.15', count=6 if split else 4
+    ):
+        simulator = cirq.DensityMatrixSimulator(
+            split_untangled_states=split, ignore_measurement_results=True
+        )
+        circuit = cirq.Circuit(cirq.H(q0), cirq.measure(q0))
+        circuit = cirq.Circuit(cirq.CircuitOperation(circuit.freeze()))
+        result = simulator.simulate(circuit)
+        np.testing.assert_almost_equal(result.final_density_matrix, np.eye(2) * 0.5)
+        assert len(result.measurements) == 0
 
 
 @pytest.mark.parametrize('dtype', [np.complex64, np.complex128])
@@ -573,24 +580,25 @@ def test_reset_one_qubit_does_not_affect_partial_trace_of_other_qubits(
 
 def test_ignore_measurements_remains_entangled():
     q0, q1 = cirq.LineQubit.range(2)
-    simulator1 = cirq.DensityMatrixSimulator(
-        ignore_measurement_results=True, split_untangled_states=False
-    )
-    simulator2 = cirq.DensityMatrixSimulator(
-        ignore_measurement_results=True, split_untangled_states=True
-    )
-    circuit = cirq.Circuit(
-        cirq.H(q0),
-        cirq.CX(q0, q1),
-        cirq.measure(q0),
-    )
-    result1 = simulator1.simulate(circuit)
-    result2 = simulator2.simulate(circuit)
-    np.testing.assert_almost_equal(result2.final_density_matrix, result1.final_density_matrix)
-    expected = np.zeros((4, 4))
-    expected[0, 0] = 0.5
-    expected[3, 3] = 0.5
-    np.testing.assert_almost_equal(result2.final_density_matrix, expected)
+    with cirq.testing.assert_deprecated('ignore_measurement_results', deadline='v0.15', count=12):
+        simulator1 = cirq.DensityMatrixSimulator(
+            ignore_measurement_results=True, split_untangled_states=False
+        )
+        simulator2 = cirq.DensityMatrixSimulator(
+            ignore_measurement_results=True, split_untangled_states=True
+        )
+        circuit = cirq.Circuit(
+            cirq.H(q0),
+            cirq.CX(q0, q1),
+            cirq.measure(q0),
+        )
+        result1 = simulator1.simulate(circuit)
+        result2 = simulator2.simulate(circuit)
+        np.testing.assert_almost_equal(result2.final_density_matrix, result1.final_density_matrix)
+        expected = np.zeros((4, 4))
+        expected[0, 0] = 0.5
+        expected[3, 3] = 0.5
+        np.testing.assert_almost_equal(result2.final_density_matrix, expected)
 
 
 @pytest.mark.parametrize(
@@ -1225,13 +1233,14 @@ def with_qubits(self, *new_qubits):
         def _kraus_(self):
             return cirq.kraus(cirq.H)
 
-    s = cirq.DensityMatrixSimulator(ignore_measurement_results=True)
-    c = cirq.Circuit(HAsOp(cirq.LineQubit(0)))
-    np.testing.assert_allclose(
-        s.simulate(c).final_density_matrix,
-        [[0.5 + 0.0j, 0.5 + 0.0j], [0.5 + 0.0j, 0.5 + 0.0j]],
-        atol=1e-8,
-    )
+    with cirq.testing.assert_deprecated('ignore_measurement_results', deadline='v0.15', count=6):
+        s = cirq.DensityMatrixSimulator(ignore_measurement_results=True)
+        c = cirq.Circuit(HAsOp(cirq.LineQubit(0)))
+        np.testing.assert_allclose(
+            s.simulate(c).final_density_matrix,
+            [[0.5 + 0.0j, 0.5 + 0.0j], [0.5 + 0.0j, 0.5 + 0.0j]],
+            atol=1e-8,
+        )
 
 
 def test_works_on_pauli_string_phasor():

cirq/sim/simulator_base.py

@@ -36,6 +36,7 @@
 import numpy as np
 
 from cirq import ops, protocols, study, value, devices
+from cirq._compat import deprecated_parameter
 from cirq.sim import ActOnArgsContainer
 from cirq.sim.operation_target import OperationTarget
 from cirq.sim.simulator import (
@@ -92,6 +93,12 @@ class SimulatorBase(
     `_core_iterator` and `_run` methods.
     """
 
+    @deprecated_parameter(
+        deadline='v0.15',
+        fix='Use cirq.dephase_measurements to transform the circuit before simulating.',
+        parameter_desc='ignore_measurement_results',
+        match=lambda _, kwargs: 'ignore_measurement_results' in kwargs,
+    )
     def __init__(
         self,
         *,

cirq/transformers/measurement_transformers_test.py

@@ -39,18 +39,19 @@ def assert_equivalent_to_deferred(circuit: cirq.Circuit):
 
 def assert_equivalent_to_dephased(circuit: cirq.Circuit):
     qubits = list(circuit.all_qubits())
-    sim = cirq.DensityMatrixSimulator(ignore_measurement_results=True)
-    num_qubits = len(qubits)
-    backwards = list(circuit.all_operations())[::-1]
-    for j in range(num_qubits):
-        backwards.append(cirq.H(qubits[j]) ** np.random.rand())
-    modified = cirq.Circuit(backwards[::-1])
-    for j in range(num_qubits):
-        modified.append(cirq.H(qubits[j]) ** np.random.rand())
-    dephased = cirq.dephase_measurements(modified)
-    result = sim.simulate(modified)
-    result1 = sim.simulate(dephased)
-    np.testing.assert_almost_equal(result.final_density_matrix, result1.final_density_matrix)
+    with cirq.testing.assert_deprecated('ignore_measurement_results', deadline='v0.15', count=14):
+        sim = cirq.DensityMatrixSimulator(ignore_measurement_results=True)
+        num_qubits = len(qubits)
+        backwards = list(circuit.all_operations())[::-1]
+        for j in range(num_qubits):
+            backwards.append(cirq.H(qubits[j]) ** np.random.rand())
+        modified = cirq.Circuit(backwards[::-1])
+        for j in range(num_qubits):
+            modified.append(cirq.H(qubits[j]) ** np.random.rand())
+        dephased = cirq.dephase_measurements(modified)
+        result = sim.simulate(modified)
+        result1 = sim.simulate(dephased)
+        np.testing.assert_almost_equal(result.final_density_matrix, result1.final_density_matrix)
 
 
 def test_basic():