Function that applies the pattern matching algorithm and returns the list of maximal matches.
circuit_dag (CommutationDAG) – A commutation DAG representing the circuit to be optimized.
pattern_dag (CommutationDAG) – A commutation DAG representing the pattern.
the list of maximal matches.
- Return type
First let’s consider the following circuit
def circuit(): qml.S(wires=0) qml.PauliZ(wires=0) qml.S(wires=1) qml.CZ(wires=[0, 1]) qml.S(wires=1) qml.S(wires=2) qml.CZ(wires=[1, 2]) qml.S(wires=2) return qml.expval(qml.PauliX(wires=0))
Assume that we want to find all maximal matches of a pattern containing a sequence of two
Sgates and a
def pattern(): qml.S(wires=0) qml.S(wires=0) qml.PauliZ(wires=0)
>>> circuit_dag = qml.commutation_dag(circuit)() >>> pattern_dag = qml.commutation_dag(pattern)() >>> all_max_matches = qml.pattern_matching(circuit_dag, pattern_dag)
The matches are accessible by looping through the list outputted by
qml.pattern_matching. This output is a list of lists containing indices. Each list represents a match between a gate in the pattern with a gate in the circuit. The first indices represent the gates in the pattern and the second indices provide indices for the gates in the circuit (by order of appearance).
>>> for match_conf in all_max_matches: ... print(match_conf.match) [[0, 0], [2, 1]] [[0, 2], [1, 4]] [[0, 4], [1, 2]] [[0, 5], [1, 7]] [[0, 7], [1, 5]]
The first match of this list corresponds to match the first gate (
S) in the pattern with the first gate in the circuit and also the third gate in the pattern (
PauliZ) with the second circuit gate.
 Iten, R., Moyard, R., Metger, T., Sutter, D. and Woerner, S., 2022. Exact and practical pattern matching for quantum circuit optimization. doi.org/10.1145/3498325
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