text: 377,7,1378103690221998080,899120403649404928,Sam Cree,"New paper! To build a good quantum computer, we need to encode information so that it can be processed without getting corrupted. We found that certain codes inspired by quantum gravity only allow very limited kinds of fault-tolerant processing. 💻⚛️🤔 <LINK> 1/4 <LINK> Context: theorists have been using holographic codes as toy models of quantum gravity for the last few years. They do a decent job at protecting information from errors/environmental noise, but their usefulness for fault-tolerant quantum computing is unclear. 2/4 Our contribution: The kinds of fault-tolerant operations you can do most easily in holographic codes are very restricted - you can't implement non-Clifford gates, which are often the ""magic ingredient"" in universal fault-tolerant quantum computation strategies. 3/4 So holographic codes might yet find a practical application for quantum computing, but we've ruled out the most straightforward way we might have hoped for. 4/4 Thanks to coauthors, @DomJWilliamson, @KfirDolev and Vlad Calvera #quantph #quantum #scicomm #sciencetwitter #arxiv",https://arxiv.org/abs/2103.13404,"We evaluate the usefulness of holographic stabilizer codes for practical purposes by studying their allowed sets of fault-tolerantly implementable gates. We treat them as subsystem codes and show that the set of transversally implementable logical operations is contained in the Clifford group for sufficiently localized logical subsystems. As well as proving this concretely for several specific codes, we argue that this restriction naturally arises in any stabilizer subsystem code that comes close to capturing certain properties of holography. We extend these results to approximate encodings, locality-preserving gates, certain codes whose logical algebras have non-trivial centers, and discuss cases where restrictions can be made to other levels of the Clifford hierarchy. A few auxiliary results may also be of interest, including a general definition of entanglement wedge map for any subsystem code, and a thorough classification of different correctability properties for regions in a subsystem code. ","Fault-tolerant logical gates in holographic stabilizer codes are