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Add cirq.toggle_tags helper to apply transformers on specific subsets of operations in a circuit #4973

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merged 3 commits into from
Feb 10, 2022
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Add cirq.toggle_tags helper to apply transformers on specific subsets of operations in a circuit #4973

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d84e9c7
Add helper to apply transformers on specific subsets of operations i…
tanujkhattar Feb 10, 2022
9a3c54e
Merge branch 'master' of https://github.com/quantumlib/cirq into xor_…
tanujkhattar Feb 10, 2022
64297ae
Rename to toggle_tags and address feedback
tanujkhattar Feb 10, 2022
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1 change: 1 addition & 0 deletions cirq-core/cirq/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,7 @@
unroll_circuit_op,
unroll_circuit_op_greedy_earliest,
unroll_circuit_op_greedy_frontier,
xor_ops_with_tags,
)

from cirq.qis import (
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1 change: 1 addition & 0 deletions cirq-core/cirq/transformers/__init__.py
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Expand Up @@ -77,4 +77,5 @@
unroll_circuit_op,
unroll_circuit_op_greedy_earliest,
unroll_circuit_op_greedy_frontier,
xor_ops_with_tags,
)
34 changes: 34 additions & 0 deletions cirq-core/cirq/transformers/align_test.py
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Expand Up @@ -71,6 +71,40 @@ def test_align_left_no_compile_context():
)


def test_align_left_subset_of_operations():
q1 = cirq.NamedQubit('q1')
q2 = cirq.NamedQubit('q2')
tag = "op_to_align"
c_orig = cirq.Circuit(
[
cirq.Moment([cirq.Y(q1)]),
cirq.Moment([cirq.X(q2)]),
cirq.Moment([cirq.X(q1).with_tags(tag)]),
cirq.Moment([cirq.Y(q2)]),
cirq.measure(*[q1, q2], key='a'),
]
)
c_exp = cirq.Circuit(
[
cirq.Moment([cirq.Y(q1)]),
cirq.Moment([cirq.X(q1).with_tags(tag), cirq.X(q2)]),
cirq.Moment(),
cirq.Moment([cirq.Y(q2)]),
cirq.measure(*[q1, q2], key='a'),
]
)
cirq.testing.assert_same_circuits(
cirq.xor_ops_with_tags(
cirq.align_left(
cirq.xor_ops_with_tags(c_orig, [tag]),
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What is going on here? Is the xor a necessary step for alignment, or just a test element to verify proper behavior of align_left?

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So in the example here, directly doing an align_left on the entire circuit would cause both X(q1) and Y(q2) in moments 2 & 3 (0-based indexing) to move left. But by adding a tag to X(q1) and using xor_ops_with_tags to toggle tags --> do optimization --> toggle tags again, we are able to do the transformation only the subset of operations that are tagged -- therefore only X(q1) aligns to the left but Y(q2) stays in-place.

context=cirq.TransformerContext(tags_to_ignore=[tag]),
),
[tag],
),
c_exp,
)


def test_align_right_no_compile_context():
q1 = cirq.NamedQubit('q1')
q2 = cirq.NamedQubit('q2')
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15 changes: 15 additions & 0 deletions cirq-core/cirq/transformers/transformer_primitives.py
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Expand Up @@ -426,3 +426,18 @@ def unroll_circuit_op_greedy_frontier(
)
frontier = unrolled_circuit.insert_at_frontier(sub_circuit.all_operations(), idx, frontier)
return _to_target_circuit_type(unrolled_circuit, circuit)


def xor_ops_with_tags(circuit: CIRCUIT_TYPE, tags: Sequence[Hashable], *, deep: bool = False):
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Please add a function docstring.

Also, I'm not sure about this name - we're not xor'ing ops, we're xor'ing their tags. Maybe (as used in the test) "flip_tags" or "toggle_tags" would be clearer?

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Yeah, naming this method is hard. changed to toggle_tags and added a docstring

tags_to_xor = set(tags)

def map_func(op: 'cirq.Operation', _) -> 'cirq.Operation':
op_tags = set(op.tags)
new_tags = (op_tags - tags_to_xor) | (tags_to_xor - op_tags)
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return (
op
if deep and isinstance(op, circuits.CircuitOperation)
else op.untagged.with_tags(*new_tags)
)

return map_operations(circuit, map_func, deep=deep)
16 changes: 16 additions & 0 deletions cirq-core/cirq/transformers/transformer_primitives_test.py
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Expand Up @@ -166,6 +166,22 @@ def test_map_operations_respects_tags_to_ignore():
)


def test_apply_tag_to_inverted_op_set():
q = cirq.LineQubit.range(2)
op = cirq.CNOT(*q)
tag = "tag_to_flip"
c_orig = cirq.Circuit(op, op.with_tags(tag), cirq.CircuitOperation(cirq.FrozenCircuit(op)))
c_flipped_with_deep = cirq.Circuit(
op.with_tags(tag), op, cirq.CircuitOperation(cirq.FrozenCircuit(op.with_tags(tag)))
)
c_flipped_without_deep = cirq.Circuit(
op.with_tags(tag), op, cirq.CircuitOperation(cirq.FrozenCircuit(op)).with_tags(tag)
)
for c_flip, deep in zip([c_flipped_with_deep, c_flipped_without_deep], [True, False]):
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cirq.testing.assert_same_circuits(cirq.xor_ops_with_tags(c_orig, [tag], deep=deep), c_flip)
cirq.testing.assert_same_circuits(cirq.xor_ops_with_tags(c_flip, [tag], deep=deep), c_orig)


def test_unroll_circuit_op_and_variants():
q = cirq.LineQubit.range(2)
c = cirq.Circuit(cirq.X(q[0]), cirq.CNOT(q[0], q[1]), cirq.X(q[0]))
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