conference paper published Sevag Gharibian author 715410000-0002-9992-3379 Dorian Rudolph author 623 department 7 department Savitch's theorem states that NPSPACE computations can be simulated in PSPACE. We initiate the study of a quantum analogue of NPSPACE, denoted Streaming-QCMASPACE (SQCMASPACE), where an exponentially long classical proof is streamed to a poly-space quantum verifier. Besides two main results, we also show that a quantum analogue of Savitch's theorem is unlikely to hold, as SQCMASPACE=NEXP. For completeness, we introduce Streaming-QMASPACE (SQMASPACE) with an exponentially long streamed quantum proof, and show SQMASPACE=QMA_EXP (quantum analogue of NEXP). Our first main result shows, in contrast to the classical setting, the solution space of a quantum constraint satisfaction problem (i.e. a local Hamiltonian) is always connected when exponentially long proofs are permitted. For this, we show how to simulate any Lipschitz continuous path on the unit hypersphere via a sequence of local unitary gates, at the expense of blowing up the circuit size. This shows quantum error-correcting codes can be unable to detect one codeword erroneously evolving to another if the evolution happens sufficiently slowly, and answers an open question of [Gharibian, Sikora, ICALP 2015] regarding the Ground State Connectivity problem. Our second main result is that any SQCMASPACE computation can be embedded into "unentanglement", i.e. into a quantum constraint satisfaction problem with unentangled provers. Formally, we show how to embed SQCMASPACE into the Sparse Separable Hamiltonian problem of [Chailloux, Sattath, CCC 2012] (QMA(2)-complete for 1/poly promise gap), at the expense of scaling the promise gap with the streamed proof size. As a corollary, we obtain the first systematic construction for obtaining QMA(2)-type upper bounds on arbitrary multi-prover interactive proof systems, where the QMA(2) promise gap scales exponentially with the number of bits of communication in the interactive proof. 2023 eng 2206.0524310.4230/LIPIcs.ITCS.2023.53 25153:1-53:23 Gharibian S, Rudolph D. Quantum space, ground space traversal, and how to embed multi-prover  interactive proofs into unentanglement. In: <i>14th Innovations in Theoretical Computer Science (ITCS)</i>. Vol 251. ; 2023:53:1-53:23. doi:<a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">10.4230/LIPIcs.ITCS.2023.53</a> @inproceedings{Gharibian_Rudolph_2023, title={Quantum space, ground space traversal, and how to embed multi-prover  interactive proofs into unentanglement}, volume={251}, DOI={<a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">10.4230/LIPIcs.ITCS.2023.53</a>}, booktitle={14th Innovations in Theoretical Computer Science (ITCS)}, author={Gharibian, Sevag and Rudolph, Dorian}, year={2023}, pages={53:1-53:23} } Gharibian, Sevag, and Dorian Rudolph. “Quantum Space, Ground Space Traversal, and How to Embed Multi-Prover  Interactive Proofs into Unentanglement.” <i>14th Innovations in Theoretical Computer Science (ITCS)</i>, vol. 251, 2023, p. 53:1-53:23, doi:<a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">10.4230/LIPIcs.ITCS.2023.53</a>. S. Gharibian, D. Rudolph, in: 14th Innovations in Theoretical Computer Science (ITCS), 2023, p. 53:1-53:23. Gharibian, Sevag, and Dorian Rudolph. “Quantum Space, Ground Space Traversal, and How to Embed Multi-Prover  Interactive Proofs into Unentanglement.” In <i>14th Innovations in Theoretical Computer Science (ITCS)</i>, 251:53:1-53:23, 2023. <a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">https://doi.org/10.4230/LIPIcs.ITCS.2023.53</a>. Gharibian, S., &#38; Rudolph, D. (2023). Quantum space, ground space traversal, and how to embed multi-prover  interactive proofs into unentanglement. <i>14th Innovations in Theoretical Computer Science (ITCS)</i>, <i>251</i>, 53:1-53:23. <a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">https://doi.org/10.4230/LIPIcs.ITCS.2023.53</a> S. Gharibian and D. Rudolph, “Quantum space, ground space traversal, and how to embed multi-prover  interactive proofs into unentanglement,” in <i>14th Innovations in Theoretical Computer Science (ITCS)</i>, 2023, vol. 251, p. 53:1-53:23, doi: <a href="https://doi.org/10.4230/LIPIcs.ITCS.2023.53">10.4230/LIPIcs.ITCS.2023.53</a>. 318722022-06-13T14:40:46Z2023-02-28T11:06:55Z