Fault-tolerant quantum computation using two-dimensional topological quantum error correcting codes can benefit from multi-qubit long-range operations. By using simple commutation rules, a quantum circuit can be transpiled into a sequence of solely non-Clifford multi-qubit gates. Prior work on fault-tolerant compilation avoids optimal scheduling of such gates since they reduce the parallelizability of the circuit. We observe that the reduced parallelization potential is outweighed by the significant reduction in the number of gates. We therefore devise a method for scheduling multi-qubit lattice surgery using an earliest-available-first policy, solving the associated forest packing problem using a representation of the multi-qubit gates as Steiner trees. Our extensive testing on random and various Hamiltonian simulation circuits demonstrates the method’s scalability and performance. We show that the transpilation significantly reduces the circuit length on the set of circuits tested, and that the resulting circuit of multi-qubit gates has a further reduction in the expected circuit execution time compared to serial execution.
@InProceedings{silva_et_al:LIPIcs.TQC.2024.1, author = {Silva, Allyson and Zhang, Xiangyi and Webb, Zak and Kramer, Mia and Yang, Chan-Woo and Liu, Xiao and Lemieux, Jessica and Chen, Ka-Wai and Scherer, Artur and Ronagh, Pooya}, title = {{Multi-qubit Lattice Surgery Scheduling}}, booktitle = {19th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2024)}, pages = {1:1--1:22}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-328-7}, ISSN = {1868-8969}, year = {2024}, volume = {310}, editor = {Magniez, Fr\'{e}d\'{e}ric and Grilo, Alex Bredariol}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2024.1}, URN = {urn:nbn:de:0030-drops-206712}, doi = {10.4230/LIPIcs.TQC.2024.1}, annote = {Keywords: Scheduling, Large-Scale Optimization, Surface Code, Quantum Compilation, Circuit Optimization} }
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