eprintid: 10198915 rev_number: 15 eprint_status: archive userid: 699 dir: disk0/10/19/89/15 datestamp: 2024-10-25 15:55:16 lastmod: 2024-10-25 16:00:21 status_changed: 2024-10-25 15:55:16 type: article metadata_visibility: show sword_depositor: 699 creators_name: Feinstein, Natasha creators_name: Fry-Bouriaux, Louis creators_name: Bose, Sougato creators_name: Warburton, PA title: Effects of Effects of XX catalysts on quantum annealing spectra with perturbative crossings ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F46 divisions: F60 divisions: F64 note: Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. abstract: In adiabatic quantum computation the required run-time to reach a given ground-state fidelity is dictated by the size of the minimum gap that appears between the ground and first-excited state in the annealing spectrum. In general the presence of avoided level crossings demands an exponential increase in the annealing time with the system size which has consequences both for the efficiency of the algorithm and the required qubit coherence times. One promising avenue being explored to produce more favorable gap scaling is the introduction of nonstoquastic XX couplings in the form of a catalyst—of particular interest are catalysts which utilize accessible information about the optimization problem in their construction. Here we show extreme sensitivity of the effect of an XX catalyst to subtle changes in the encoding of the optimization problem. In particular, we observe that a targeted catalyst containing a single coupling can significantly reduce the gap closing with system size at an avoided level crossing. For slightly different encodings of the same problems however, these same catalysts result in closing gaps in the annealing spectrum. To understand the origin of these closing gaps, we study how the evolution of the ground-state vector is altered by the presence of the catalyst and find that the negative components of the ground-state vector are key to understanding the response of the gap spectrum. We also consider how and when these closing gaps could be utilized in diabatic quantum annealing protocols—a promising alternative to adiabatic quantum annealing in which transitions to higher energy levels are exploited to reduce the run time of the algorithm. date: 2024-10-10 date_type: published publisher: American Physical Society (APS) official_url: https://doi.org/10.1103/PhysRevA.110.042609 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 2327224 doi: 10.1103/physreva.110.042609 lyricists_name: Bose, Sougato lyricists_name: Warburton, Paul lyricists_name: Feinstein, Natasha lyricists_id: SBOSE77 lyricists_id: PAWAR27 lyricists_id: NJSFE43 actors_name: Feinstein, Natasha actors_id: NJSFE43 actors_role: owner full_text_status: public publication: Physical Review A volume: 110 number: 4 article_number: 042609 issn: 2469-9926 citation: Feinstein, Natasha; Fry-Bouriaux, Louis; Bose, Sougato; Warburton, PA; (2024) Effects of Effects of XX catalysts on quantum annealing spectra with perturbative crossings. Physical Review A , 110 (4) , Article 042609. 10.1103/physreva.110.042609 <https://doi.org/10.1103/physreva.110.042609>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10198915/1/effects_of_XX_catalysts_on_perturbative_crossings.pdf