{"title":"Homological product codes","authors":"S. Bravyi, M. Hastings","doi":"10.1145/2591796.2591870","DOIUrl":"https://doi.org/10.1145/2591796.2591870","url":null,"abstract":"Quantum codes with low-weight stabilizers known as LDPC codes have been actively studied recently due to their potential applications in fault-tolerant quantum computing. However, all families of quantum LDPC codes known to this date suffer from a poor distance scaling limited by the square-root of the code length. This is in a sharp contrast with the classical case where good families of LDPC codes are known that combine constant encoding rate and linear distance. Here we propose the first family of good quantum codes with low-weight stabilizers. The new codes have a constant encoding rate, linear distance, and stabilizers acting on at most O(√n) qubits, where n is the code length. For comparison, all previously known families of good quantum codes have stabilizers of linear weight. Our proof combines two techniques: randomized constructions of good quantum codes and the homological product operation from algebraic topology. We conjecture that similar methods can produce good stabilizer codes with stabilizer weight O(nα) for any α > 0.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115672913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bandits with switching costs: T2/3 regret","authors":"O. Dekel, Jian Ding, Tomer Koren, Y. Peres","doi":"10.1145/2591796.2591868","DOIUrl":"https://doi.org/10.1145/2591796.2591868","url":null,"abstract":"We study the adversarial multi-armed bandit problem in a setting where the player incurs a unit cost each time he switches actions. We prove that the player's T-round minimax regret in this setting is [EQUATION], thereby closing a fundamental gap in our understanding of learning with bandit feedback. In the corresponding full-information version of the problem, the minimax regret is known to grow at a much slower rate of Θ(√T). The difference between these two rates provides the first indication that learning with bandit feedback can be significantly harder than learning with full information feedback (previous results only showed a different dependence on the number of actions, but not on T.) In addition to characterizing the inherent difficulty of the multi-armed bandit problem with switching costs, our results also resolve several other open problems in online learning. One direct implication is that learning with bandit feedback against bounded-memory adaptive adversaries has a minimax regret of [EQUATION]. Another implication is that the minimax regret of online learning in adversarial Markov decision processes (MDPs) is [EQUATION]. The key to all of our results is a new randomized construction of a multi-scale random walk, which is of independent interest and likely to prove useful in additional settings.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"47 43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123996715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The asymptotic k-SAT threshold","authors":"A. Coja-Oghlan","doi":"10.1145/2591796.2591822","DOIUrl":"https://doi.org/10.1145/2591796.2591822","url":null,"abstract":"Since the early 2000s physicists have developed an ingenious but non-rigorous formalism called the cavity method to put forward precise conjectures as to the phase transitions in random constraint satisfaction problems (\"CSPs\"). The cavity method comes in two versions: the simpler replica symmetric variant, and the more intricate 1-step replica symmetry breaking (\"1RSB\") version. While typically the former only gives upper and lower bounds, the latter is conjectured to yield precise results in many cases. By now, there are a number of examples where the replica symmetric bounds have been verified rigorously. However, verifications of 1RSB predictions are scarce. Perhaps the most prominent challenge in this context is that of pinning down the random k-SAT threshold rk--SAT. Here we prove that rk--SAT = 2k ln 2--1/2 (1 + ln 2) + ok(1), which matches the 1RSB prediction up to the ok(1) error term. The proof directly employs ideas from the 1RSB cavity method, such as the notion of covers (relaxed satisfying assignments) and bits of the Survey Propagation calculations. The best previous lower bound was rk--SAT ≥ 2k ln 2--3/2 ln 2 + ok(1), matching the replica symmetric lower bound asymptotically [Coja-Oghlan, Panagiotou: STOC 2013].","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126601615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Every list-decodable code for high noise has abundant near-optimal rate puncturings","authors":"A. Rudra, Mary Wootters","doi":"10.1145/2591796.2591797","DOIUrl":"https://doi.org/10.1145/2591796.2591797","url":null,"abstract":"We show that any q-ary code with sufficiently good distance can be randomly punctured to obtain, with high probability, a code that is list decodable up to radius 1 --- 1/q --- ε with near-optimal rate and list sizes. Our results imply that \"most\" Reed-Solomon codes are list decodable beyond the Johnson bound, settling the longstanding open question of whether any Reed Solomon codes meet this criterion. More precisely, we show that a Reed-Solomon code with random evaluation points is, with high probability, list decodable up to radius 1 --- ε with list sizes O(1/ε) and rate Ω(ε). As a second corollary of our argument, we obtain improved bounds on the list decodability of random linear codes over large fields. Our approach exploits techniques from high dimensional probability. Previous work used similar tools to obtain bounds on the list decodability of random linear codes, but the bounds did not scale with the size of the alphabet. In this paper, we use a chaining argument to deal with large alphabet sizes.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115051991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multiway cut, pairwise realizable distributions, and descending thresholds","authors":"Ankit Sharma, J. Vondrák","doi":"10.1145/2591796.2591866","DOIUrl":"https://doi.org/10.1145/2591796.2591866","url":null,"abstract":"We design new approximation algorithms for the Multiway Cut problem, improving the previously known factor of 1.32388 [Buchbinder et al., 2013]. We proceed in three steps. First, we analyze the rounding scheme of Buchbinder et al. [2013] and design a modification that improves the approximation to [EQUATION]. We also present a tight example showing that this is the best approximation one can achieve with the type of cuts considered by Buchbinder et al. [2013]: (1) partitioning by exponential clocks, and (2) single-coordinate cuts with equal thresholds. Then, we prove that this factor can be improved by introducing a new rounding scheme: (3) single-coordinate cuts with descending thresholds. By combining these three schemes, we design an algorithm that achieves a factor of [EQUATION]. This is the best approximation factor that we are able to verify by hand. Finally, we show that by combining these three rounding schemes with the scheme of independent thresholds from Karger et al. [2004], the approximation factor can be further improved to 1.2965. This approximation factor has been verified only by computer.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132900314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Testing surface area with arbitrary accuracy","authors":"Joe Neeman","doi":"10.1145/2591796.2591807","DOIUrl":"https://doi.org/10.1145/2591796.2591807","url":null,"abstract":"Recently, Kothari et al. gave an algorithm for testing the surface area of an arbitrary set A ⊂ [0,1]n. Specifically, they gave a randomized algorithm such that if A's surface area is less than S then the algorithm will accept with high probability, and if the algorithm accepts with high probability then there is some perturbation of A with surface area at most κnS. Here, κn is a dimension-dependent constant which is strictly larger than 1 if n ≥ 2, and grows to 4/π as n → ∞. We give an improved analysis of Kothari et al.'s algorithm. In doing so, we replace the constant κn with 1+η for η > 0 arbitrary. We also extend the algorithm to more general measures on Riemannian manifolds.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"412 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133401940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A strongly polynomial algorithm for generalized flow maximization","authors":"László A. Végh","doi":"10.1145/2591796.2591806","DOIUrl":"https://doi.org/10.1145/2591796.2591806","url":null,"abstract":"A strongly polynomial algorithm is given for the generalized flow maximization problem. It uses a new variant of the scaling technique, called continuous scaling. The main measure of progress is that within a strongly polynomial number of steps, an arc can be identified that must be tight in every dual optimal solution, and thus can be contracted.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134019065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Query complexity of approximate nash equilibria","authors":"Y. Babichenko","doi":"10.1145/2591796.2591829","DOIUrl":"https://doi.org/10.1145/2591796.2591829","url":null,"abstract":"We study the query complexity of approximate notions of Nash equilibrium in games with a large number of players n and a constant number of actions m. Our main result states that even for constant ε, the query complexity of an ε-well-supported Nash equilibrium is exponential in n.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"365 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134518484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fourier PCA and robust tensor decomposition","authors":"Navin Goyal, S. Vempala, Ying Xiao","doi":"10.1145/2591796.2591875","DOIUrl":"https://doi.org/10.1145/2591796.2591875","url":null,"abstract":"Fourier PCA is Principal Component Analysis of a matrix obtained from higher order derivatives of the logarithm of the Fourier transform of a distribution. To make this algorithmic, we develop a robust tensor decomposition method; this is also of independent interest. Our main application is the first provably polynomial-time algorithm for underdetermined ICA, i.e., learning an n × m matrix A from observations y = Ax where x is drawn from an unknown product distribution with arbitrary non-Gaussian components. The number of component distributions m can be arbitrarily higher than the dimension n and the columns of A only need to satisfy a natural and efficiently verifiable nondegeneracy condition. As a second application, we give an alternative algorithm for learning mixtures of spherical Gaussians with linearly independent means. These results also hold in the presence of Gaussian noise.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126315002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Communication is bounded by root of rank","authors":"Shachar Lovett","doi":"10.1145/2591796.2591799","DOIUrl":"https://doi.org/10.1145/2591796.2591799","url":null,"abstract":"We prove that any total boolean function of rank r can be computed by a deterministic communication protocol of complexity O(√r · log(r)). Similarly, any graph whose adjacency matrix has rank r has chromatic number at most 2O(√r · log(r)). This gives a nearly quadratic improvement in the dependence on the rank over previous results.","PeriodicalId":123501,"journal":{"name":"Proceedings of the forty-sixth annual ACM symposium on Theory of computing","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129116875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}