20.500.12556/RUL-144712 Fastest local entanglement scrambler, multistage thermalization, and a non-Hermitian phantom We study random quantum circuits and their rate of producing bipartite entanglement, specifically with respect to the choice of 2-qubit gates and the order (protocol) in which these are applied. The problem is mapped to a Markovian process, and we prove that there are large spectral equivalence classes—different configurations have the same spectrum. Optimal gates and the protocol that generate entanglement with the fastest theoretically possible rate are identified. Relaxation towards the asymptotic thermal entanglement proceeds via a series of phase transitions in the local relaxation rate, which is a consequence of non-Hermiticity. In particular, non-Hermiticity can cause the rate to be either faster or, even more interestingly, slower than predicted by the matrix eigenvalue gap. This result is caused by expansion coefficients that grow exponentially with system size, resulting in a “phantom” eigenvalue and is due to nonorthogonality of non-Hermitian eigenvectors. We numerically demonstrate that the phenomenon also occurs in random circuits with nonoptimal generic gates, random U(4) gates, and also without spatial or temporal randomness, suggesting that it could be of wide importance in other non-Hermitian settings, including correlations. statistical physics quantum physics quantum information quantum entanglement quantum gates quantum phase transitions quantum quench general physics condensed matter materials applied physics statistična fizika kvantna fizika true false true Angleški jezik Slovenski jezik Članek v reviji 2023-03-09 08:42:45 2023-03-09 08:42:46 2023-03-10 03:35:47 0000-00-00 00:00:00 2021 0 0 28 str. iss. 3, art. 031019 Vol. 11 2021 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 536.9 2160-3308 10.1103/PhysRevX.11.031019 72645891 PhysRevX.11.031019.pdf PhysRevX.11.031019.pdf 1 0C0E7F4F9A36E537D48B47CC0FD8601E 878a762a3f2f2e3bd27f1c86de91dbc562d792a19f4fb7f532d51a99790ba32a 57221a70-be4e-11ed-a314-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=167182 https://journals.aps.org/prx/abstract/10.1103/PhysRevX.11.031019 0 49283873-be4e-11ed-a314-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=167181 Fakulteta za matematiko in fiziko 0 0 0