[{"type":"conference","publication":"16th Innovations in Theoretical Computer Science (ITCS)","status":"public","abstract":[{"lang":"eng","text":"Despite the fundamental role the Quantum Satisfiability (QSAT) problem has\r\nplayed in quantum complexity theory, a central question remains open: At which\r\nlocal dimension does the complexity of QSAT transition from \"easy\" to \"hard\"?\r\nHere, we study QSAT with each constraint acting on a $k$-dimensional and\r\n$l$-dimensional qudit pair, denoted $(k,l)$-QSAT. Our first main result shows\r\nthat, surprisingly, QSAT on qubits can remain $\\mathsf{QMA}_1$-hard, in that\r\n$(2,5)$-QSAT is $\\mathsf{QMA}_1$-complete. In contrast, $2$-SAT on qubits is\r\nwell-known to be poly-time solvable [Bravyi, 2006]. Our second main result\r\nproves that $(3,d)$-QSAT on the 1D line with $d\\in O(1)$ is also\r\n$\\mathsf{QMA}_1$-hard. Finally, we initiate the study of 1D $(2,d)$-QSAT by\r\ngiving a frustration-free 1D Hamiltonian with a unique, entangled ground state.\r\n  Our first result uses a direct embedding, combining a novel clock\r\nconstruction with the 2D circuit-to-Hamiltonian construction of [Gosset, Nagaj,\r\n2013]. Of note is a new simplified and analytic proof for the latter (as\r\nopposed to a partially numeric proof in [GN13]). This exploits Unitary Labelled\r\nGraphs [Bausch, Cubitt, Ozols, 2017] together with a new \"Nullspace Connection\r\nLemma\", allowing us to break low energy analyses into small patches of\r\nprojectors, and to improve the soundness analysis of [GN13] from\r\n$\\Omega(1/T^6)$ to $\\Omega(1/T^2)$, for $T$ the number of gates. Our second\r\nresult goes via black-box reduction: Given an arbitrary 1D Hamiltonian $H$ on\r\n$d'$-dimensional qudits, we show how to embed it into an effective null-space\r\nof a 1D $(3,d)$-QSAT instance, for $d\\in O(1)$. Our approach may be viewed as a\r\nweaker notion of \"simulation\" (\\`a la [Bravyi, Hastings 2017], [Cubitt,\r\nMontanaro, Piddock 2018]). As far as we are aware, this gives the first\r\n\"black-box simulation\"-based $\\mathsf{QMA}_1$-hardness result, i.e. for\r\nfrustration-free Hamiltonians."}],"user_id":"71541","external_id":{"arxiv":["2401.02368"]},"_id":"50272","language":[{"iso":"eng"}],"issue":"85","publication_status":"published","citation":{"apa":"Rudolph, D., Gharibian, S., &#38; Nagaj, D. (2025). Quantum 2-SAT on low dimensional systems is $\\mathsf{QMA}_1$-complete:  Direct embeddings and black-box simulation. <i>16th Innovations in Theoretical Computer Science (ITCS)</i>, <i>325</i>(85), 1–24. <a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">https://doi.org/10.4230/LIPIcs.ITCS.2025.85</a>","bibtex":"@inproceedings{Rudolph_Gharibian_Nagaj_2025, title={Quantum 2-SAT on low dimensional systems is $\\mathsf{QMA}_1$-complete:  Direct embeddings and black-box simulation}, volume={325}, DOI={<a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">10.4230/LIPIcs.ITCS.2025.85</a>}, number={85}, booktitle={16th Innovations in Theoretical Computer Science (ITCS)}, author={Rudolph, Dorian and Gharibian, Sevag and Nagaj, Daniel}, year={2025}, pages={1–24} }","mla":"Rudolph, Dorian, et al. “Quantum 2-SAT on Low Dimensional Systems Is $\\mathsf{QMA}_1$-Complete:  Direct Embeddings and Black-Box Simulation.” <i>16th Innovations in Theoretical Computer Science (ITCS)</i>, vol. 325, no. 85, 2025, pp. 1–24, doi:<a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">10.4230/LIPIcs.ITCS.2025.85</a>.","short":"D. Rudolph, S. Gharibian, D. Nagaj, in: 16th Innovations in Theoretical Computer Science (ITCS), 2025, pp. 1–24.","ama":"Rudolph D, Gharibian S, Nagaj D. Quantum 2-SAT on low dimensional systems is $\\mathsf{QMA}_1$-complete:  Direct embeddings and black-box simulation. In: <i>16th Innovations in Theoretical Computer Science (ITCS)</i>. Vol 325. ; 2025:1-24. doi:<a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">10.4230/LIPIcs.ITCS.2025.85</a>","chicago":"Rudolph, Dorian, Sevag Gharibian, and Daniel Nagaj. “Quantum 2-SAT on Low Dimensional Systems Is $\\mathsf{QMA}_1$-Complete:  Direct Embeddings and Black-Box Simulation.” In <i>16th Innovations in Theoretical Computer Science (ITCS)</i>, 325:1–24, 2025. <a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">https://doi.org/10.4230/LIPIcs.ITCS.2025.85</a>.","ieee":"D. Rudolph, S. Gharibian, and D. Nagaj, “Quantum 2-SAT on low dimensional systems is $\\mathsf{QMA}_1$-complete:  Direct embeddings and black-box simulation,” in <i>16th Innovations in Theoretical Computer Science (ITCS)</i>, 2025, vol. 325, no. 85, pp. 1–24, doi: <a href=\"https://doi.org/10.4230/LIPIcs.ITCS.2025.85\">10.4230/LIPIcs.ITCS.2025.85</a>."},"page":"1-24","intvolume":"       325","year":"2025","date_created":"2024-01-07T20:09:13Z","author":[{"first_name":"Dorian","full_name":"Rudolph, Dorian","last_name":"Rudolph"},{"last_name":"Gharibian","orcid":"0000-0002-9992-3379","id":"71541","full_name":"Gharibian, Sevag","first_name":"Sevag"},{"last_name":"Nagaj","full_name":"Nagaj, Daniel","first_name":"Daniel"}],"volume":325,"date_updated":"2025-02-11T07:21:23Z","doi":"10.4230/LIPIcs.ITCS.2025.85","title":"Quantum 2-SAT on low dimensional systems is $\\mathsf{QMA}_1$-complete:  Direct embeddings and black-box simulation"}]