Add functionalty for determining whether pairs of moments commute #6679
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## main #6679 +/- ##
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Coverage 97.82% 97.82%
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Files 1072 1072
Lines 92047 92075 +28
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| # Decompose both moments onto each disjoint set of qubits and | ||
| # check for commutation using the unitary representation | ||
| if all( | ||
| definitely_commutes( |
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would this code raise an error if the operations are not unitary?
| @@ -669,25 +676,92 @@ def _commutes_(self, other: Any, *, atol: float = 1e-8) -> Union[bool, NotImplem | |||
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| Returns: | |||
| True: The Moment and Operation commute OR they don't have shared | |||
| quibits. | |||
| qubits. | |||
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can you fix the formatting?
| # Decompose into disjoint overlapping sets of qubits | ||
| qubit_subsets = [list(op.qubits) for op in self.operations + other.operations] | ||
| disjoint_set = DisjointSet(itertools.chain.from_iterable(qubit_subsets)) | ||
| for subset in qubit_subsets: |
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what happens if a qubit appears in both moments in operations with different qubits?
so in m1: op1 acting on (q1, q0) in m2 op2 acting on q3, q4, q0)
| if isinstance(other, ops.Operation): | ||
| # If an Operation is provided, convert this to a Moment consisting only | ||
| # of the given Operation | ||
| return self._commutes_(Moment(other), atol=atol) |
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why not preserve the old code? ... perhaps in a def _commutes_with_op
| @@ -693,6 +693,18 @@ def test_commutes(): | |||
| assert not cirq.commutes(moment, cirq.X(c)) | |||
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| def test_commutes_multiqubit_gates(): | |||
| a = cirq.NamedQubit('a') | |||
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this test case is very simple and doesn't cover the more complex cases ... see above
Currently it is not possible to determine if pairs of moments can commute which may be useful for when collections of operations commute as a group but not individually
For instance a pair of single qubit Z gates commute with a two qubit RXX gate together but not separately.
This PR fixes this challenge by decomposing two moments into operations that act on disjoint sets of qubits and then testing whether their unitary representations on these sets of qubits commute.
Closes #6659