ترغب بنشر مسار تعليمي؟ اضغط هنا

The Garden Hose Complexity for the Equality Function

52   0   0.0 ( 0 )
 نشر من قبل Yixin Xu
 تاريخ النشر 2013
والبحث باللغة English




اسأل ChatGPT حول البحث

The garden hose complexity is a new communication complexity introduced by H. Buhrman, S. Fehr, C. Schaffner and F. Speelman [BFSS13] to analyze position-based cryptography protocols in the quantum setting. We focus on the garden hose complexity of the equality function, and improve on the bounds of O. Margalit and A. Matsliah[MM12] with the help of a new approach and of our handmade simulated annealing based solver. We have also found beautiful symmetries of the solutions that have lead us to develop the notion of garden hose permutation groups. Then, exploiting this new concept, we get even further, although several interesting open problems remain.

قيم البحث

اقرأ أيضاً

In this paper, we study quantum query complexity of the following rather natural tripartite generalisations (in the spirit of the 3-sum problem) of the hidden shift and the set equality problems, which we call the 3-shift-sum and the 3-matching-sum p roblems. The 3-shift-sum problem is as follows: given a table of $3times n$ elements, is it possible to circularly shift its rows so that the sum of the elements in each column becomes zero? It is promised that, if this is not the case, then no 3 elements in the table sum up to zero. The 3-matching-sum problem is defined similarly, but it is allowed to arbitrarily permute elements within each row. For these problems, we prove lower bounds of $Omega(n^{1/3})$ and $Omega(sqrt n)$, respectively. The second lower bound is tight. The lower bounds are proven by a novel application of the dual learning graph framework and by using representation-theoretic tools.
We investigate the randomized and quantum communication complexities of the well-studied Equality function with small error probability $epsilon$, getting the optimal constant factors in the leading terms in a number of different models. In the ran domized model, 1) we give a general technique to convert public-coin protocols to private-coin protocols by incurring a small multiplicative error, at a small additive cost. This is an improvement over Newmans theorem [Inf. Proc. Let.91] in the dependence on the error parameter. 2) Using this we obtain a $(log(n/epsilon^2)+4)$-cost private-coin communication protocol that computes the $n$-bit Equality function, to error $epsilon$. This improves upon the $log(n/epsilon^3)+O(1)$ upper bound implied by Newmans theorem, and matches the best known lower bound, which follows from Alon [Comb. Prob. Comput.09], up to an additive $loglog(1/epsilon)+O(1)$. In the quantum model, 1) we exhibit a one-way protocol of cost $log(n/epsilon)+4$, that uses only pure states and computes the $n$-bit Equality function to error $epsilon$. This bound was implicitly already shown by Nayak [PhD thesis99]. 2) We show that any $epsilon$-error one-way protocol for $n$-bit Equality that uses only pure states communicates at least $log(n/epsilon)-loglog(1/epsilon)-O(1)$ qubits. 3) We exhibit a one-way protocol of cost $log(sqrt{n}/epsilon)+3$, that uses mixed states and computes the $n$-bit Equality function to error $epsilon$. This is also tight up to an additive $loglog(1/epsilon)+O(1)$, which follows from Alons result. Our upper bounds also yield upper bounds on the approximate rank and related measures of the Identity matrix. This also implies improved upper bounds on these measures for the distributed SINK function, which was recently used to refute the randomized and quant
We study the quantum query complexity of finding a certificate for a d-regular, k-level balanced NAND formula. Up to logarithmic factors, we show that the query complexity is Theta(d^{(k+1)/2}) for 0-certificates, and Theta(d^{k/2}) for 1-certificate s. In particular, this shows that the zero-error quantum query complexity of evaluating such formulas is O(d^{(k+1)/2}) (again neglecting a logarithmic factor). Our lower bound relies on the fact that the quantum adversary method obeys a direct sum theorem.
Inspired by connections to two dimensional quantum theory, we define several models of computation based on permuting distinguishable particles (which we call balls), and characterize their computational complexity. In the quantum setting, we find th at the computational power of this model depends on the initial input states. More precisely, with a standard basis input state, we show how to approximate the amplitudes of this model within additive error using the model DQC1 (the class of problems solvable with one clean qubit), providing evidence that the model in this case is weaker than universal quantum computing. However, for specific choices of input states, the model is shown to be universal for BQP in an encoded sense. We use representation theory of the symmetric group to partially classify the computational complexity of this model for arbitrary input states. Interestingly, we find some input states which yield a model intermediate between DQC1 and BQP. Furthermore, we consider a restricted version of this model based on an integrable scattering problem in 1+1 dimensions. We show it is universal under postselection, if we allow intermediate destructive measurements and specific input states. Therefore, the existence of any classical procedure to sample from the output distribution of this model within multiplicative error implies collapse of polynomial hierarchy to its third level. Finally, we define a classical version of this model in which one can probabilistically permute balls. We find this yields a complexity class which is intermediate between L and BPP. Moreover, we find a nondeterministic version of this model is NP-complete.
We identify a formal connection between physical problems related to the detection of separable (unentangled) quantum states and complexity classes in theoretical computer science. In particular, we show that to nearly every quantum interactive proof complexity class (including BQP, QMA, QMA(2), and QSZK), there corresponds a natural separability testing problem that is complete for that class. Of particular interest is the fact that the problem of determining whether an isometry can be made to produce a separable state is either QMA-complete or QMA(2)-complete, depending upon whether the distance between quantum states is measured by the one-way LOCC norm or the trace norm. We obtain strong hardness results by proving that for each n-qubit maximally entangled state there exists a fixed one-way LOCC measurement that distinguishes it from any separable state with error probability that decays exponentially in n.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا