Optimal Quantum Adversary Lower Bounds for Ordered Search

  • Andrew M. Childs
  • Troy Lee
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5125)


The goal of the ordered search problem is to find a particular item in an ordered list of n items. Using the adversary method, Høyer, Neerbek, and Shi proved a quantum lower bound for this problem of \(\frac{1}{\pi} \ln n + {\it \Theta}(1)\). Here, we find the exact value of the best possible quantum adversary lower bound for a symmetrized version of ordered search (whose query complexity differs from that of the original problem by at most 1). Thus we show that the best lower bound for ordered search that can be proved by the adversary method is \(\frac{1}{\pi} \ln n + O(1)\). Furthermore, we show that this remains true for the generalized adversary method allowing negative weights.


Automorphism Group Query Complexity Spectral Norm Negative Weight Principal Eigenvector 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Andrew M. Childs
    • 1
  • Troy Lee
    • 2
  1. 1.Department of Combinatorics & Optimization and Institute for Quantum ComputingUniversity of WaterlooCanada
  2. 2.Department of Computer ScienceRutgers UniversityUSA

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