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The Weakness of CTC Qubits and the Power of Approximate Counting

Published:23 May 2018Publication History
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Abstract

We present results in structural complexity theory concerned with the following interrelated topics: computation with postselection/restarting, closed timelike curves (CTCs), and approximate counting. The first result is a new characterization of the lesser known complexity class BPPpath in terms of more familiar concepts. Precisely, BPPpath is the class of problems that can be efficiently solved with a nonadaptive oracle for the approximate counting problem. Similarly, PP equals the class of problems that can be solved efficiently with nonadaptive queries for the related approximate difference problem. Another result is concerned with the computational power conferred by CTCs, or equivalently, the computational complexity of finding stationary distributions for quantum channels. Using the preceding characterization of PP, we show that any poly(n)-time quantum computation using a CTC of O(log n) qubits may as well just use a CTC of 1 classical bit. This result essentially amounts to showing that one can find a stationary distribution for a poly(n)-dimensional quantum channel in PP.

References

  1. Scott Aaronson. 2004. Is Quantum Mechanics an Island in Theoryspace? Technical Report quant-ph/0401062. arXiv.Google ScholarGoogle Scholar
  2. Scott Aaronson. 2004. Limits on Efficient Computation in the Physical World. Ph.D. Dissertation. University of California, Berkeley. Google ScholarGoogle ScholarDigital LibraryDigital Library
  3. Scott Aaronson. 2005. NP-complete problems and physical reality. ACM SIGACT News 36, 1, 30--52. Google ScholarGoogle ScholarDigital LibraryDigital Library
  4. Scott Aaronson. 2005. Quantum computing, postselection, and probabilistic polynomial-time. Proceedings of the Royal Society A 461, 2063, 3473--3482.Google ScholarGoogle ScholarCross RefCross Ref
  5. Scott Aaronson. 2014. PostBQP Postscripts: A Confession of Mathematical Errors. Retrieved March 21, 2018, from http://www.scottaaronson.com/blog/?p=2072.Google ScholarGoogle Scholar
  6. Scott Aaronson and Alex Arkhipov. 2011. The computational complexity of linear optics. In Proceedings of the 43rd Annual ACM Symposium on Theory of Computing. 333--342. Google ScholarGoogle ScholarDigital LibraryDigital Library
  7. Scott Aaronson and John Watrous. 2009. Closed timelike curves make quantum and classical computing equivalent. Proceedings of the Royal Society A 465, 2102, 631--647.Google ScholarGoogle ScholarCross RefCross Ref
  8. Eric Allender, Vikraman Arvind, and Meena Mahajan. 2003. Arithmetic complexity, Kleene closure, and formal power series. Theory of Computing Systems 36, 4, 303--328.Google ScholarGoogle ScholarCross RefCross Ref
  9. James Aspnes, David Fischer, Michael Fischer, Ming-Yang Kao, and Alok Kumar. 2001. Towards understanding the predictability of stock markets from the perspective of computational complexity. In Proceedings of the 12th Annual ACM-SIAM Symposium on Discrete Algorithms. 745--754. Google ScholarGoogle ScholarDigital LibraryDigital Library
  10. Dave Bacon. 2004. Quantum computational complexity in the presence of closed timelike curves. Physical Review A 70, 3, 032309.Google ScholarGoogle ScholarCross RefCross Ref
  11. Richard Beigel, Nick Reingold, and Daniel Spielman. 1995. PP is closed under intersection. Journal of Computer and System Sciences 50, 2, 191--202. Google ScholarGoogle ScholarDigital LibraryDigital Library
  12. Elmar Böhler, Christian Glaßer, and Daniel Meister. 2003. Error-bounded probabilistic computations between MA and AM. In Proceedings of the 28th Annual International Symposium on Mathematical Foundations of Computer Science. 249--258.Google ScholarGoogle ScholarCross RefCross Ref
  13. Michael Bremner, Richard Jozsa, and Dan Shepherd. 2010. Classical simulation of commuting quantum computations implies collapse of the polynomial hierarchy. Proceedings of the Royal Society A. 467, 2126, 459--472.Google ScholarGoogle Scholar
  14. David Deutsch. 1991. Quantum mechanics near closed timelike lines. Physical Review D 44, 10, 3197--3217.Google ScholarGoogle ScholarCross RefCross Ref
  15. Stephen Fenner, Frederic Green, Steven Homer, and Randall Pruim. 1999. Determining acceptance possibility for a quantum computation is hard for the polynomial hierarchy. Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 455, 1991, 3953--3966.Google ScholarGoogle ScholarCross RefCross Ref
  16. Lance Fortnow and Nick Reingold. 1996. PP is closed under truth-table reductions. Information and Computation 124, 1, 1--6. Google ScholarGoogle ScholarDigital LibraryDigital Library
  17. Lance Fortnow and John Rogers. 1999. Complexity limitations on quantum computation. Journal of Computer and System Sciences 59, 2, 240--252. Google ScholarGoogle ScholarDigital LibraryDigital Library
  18. John Gill. 1974. Computational complexity of probabilistic turing machines. In Proceedings of the 6th Annual ACM Symposium on Theory of Computing. 91--95. Google ScholarGoogle ScholarDigital LibraryDigital Library
  19. Kurt Gödel. 1949. An example of a new type of cosmological solutions of Einstein’s field equations of gravitation. Reviews of Modern Physics 21, 3, 447--450.Google ScholarGoogle ScholarCross RefCross Ref
  20. Carla Gomes, Ashish Sabharwal, and Bart Selman. 2006. Model counting: A new strategy for obtaining good bounds. In Proceedings of the National Conference on Artificial Intelligence, Vol. 21. 54. Google ScholarGoogle ScholarDigital LibraryDigital Library
  21. Yenjo Han, Lane Hemaspaandra, and Thomas Thierauf. 1997. Threshold computation and cryptographic security. SIAM Journal on Computing 26, 1, 59--78. Google ScholarGoogle ScholarDigital LibraryDigital Library
  22. Yenjo Ham, Lane Hemaspaandra, and Thomas Thierauf. 1993. Threshold computation and cryptographic security. In Proceedings of the 4th Annual International Symposium on Algorithms and Computation. 230--239. Google ScholarGoogle ScholarDigital LibraryDigital Library
  23. Ryan O’Donnell and A. C. Cem Say. 2014. One time-traveling bit is as good as logarithmically many. In Proceedings of the 35th Annual IARCS Conference on Foundations of Software Technology and Theoretical Computer Science.Google ScholarGoogle Scholar
  24. Claudia Peschiera, Luca Pulina, Armando Tacchella, Uwe Bubeck, Oliver Kullmann, and Inês Lynce. 2010. The seventh QBF solvers evaluation (QBFEVAL’10). In Theory and Applications of Satisfiability Testing—SAT 2010. Springer, 237--250. Google ScholarGoogle ScholarDigital LibraryDigital Library
  25. A. C. Cem Say and Abuzer Yakaryılmaz. 2012. Computation with multiple CTCs of fixed length and width. Natural Computing 11, 4, 579--594. Google ScholarGoogle ScholarDigital LibraryDigital Library
  26. Ronen Shaltiel and Christopher Umans. 2006. Pseudorandomness for approximate counting and sampling. Computational Complexity 15, 4, 298--341. Google ScholarGoogle ScholarDigital LibraryDigital Library
  27. Janos Simon. 1975. On Some Central Problems in Computational Complexity. Ph.D. Dissertation. Cornell University. Google ScholarGoogle ScholarDigital LibraryDigital Library
  28. Carsten Sinz and Uwe Egly (Eds.). 2014. Theory and Applications of Satisfiability Testing—SAT 2014. Lecture Notes in Computer Science, Vol. 8561. Springer.Google ScholarGoogle Scholar
  29. Michael Sipser. 1983. A complexity theoretic approach to randomness. In Proceedings of the 15th Annual ACM Symposium on Theory of Computing. 330--335. Google ScholarGoogle ScholarDigital LibraryDigital Library
  30. Larry Stockmeyer. 1983. The complexity of approximate counting. In Proceedings of the 15th Annual ACM Symposium on Theory of Computing. 118--126. Google ScholarGoogle ScholarDigital LibraryDigital Library
  31. Larry Stockmeyer. 1985. On approximation algorithms for #P. SIAM Journal on Computing 14, 4, 849--861.Google ScholarGoogle ScholarCross RefCross Ref
  32. Seinosuke Toda. 1991. PP is as hard as the polynomial-time hierarchy. SIAM Journal on Computing 20, 5, 865--877. Google ScholarGoogle ScholarDigital LibraryDigital Library
  33. John Watrous. 2008. Quantum Computational Complexity. Technical Report 0804.3401. arXiv.Google ScholarGoogle Scholar
  34. Michael Wolf. 2012. Quantum Channels and Operations: Guided Tour. Retrieved March 21, 2018, from http://www-m5.ma.tum.de/foswiki/pub/M5/Allgemeines/MichaelWolf/QChannelLecture.pdf.Google ScholarGoogle Scholar
  35. Abuzer Yakaryılmaz and A. C. Cem Say. 2013. Proving the power of postselection. Fundamenta Informaticae 123, 1, 107--134. Google ScholarGoogle ScholarDigital LibraryDigital Library

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      • Published in

        cover image ACM Transactions on Computation Theory
        ACM Transactions on Computation Theory  Volume 10, Issue 2
        June 2018
        122 pages
        ISSN:1942-3454
        EISSN:1942-3462
        DOI:10.1145/3208321
        Issue’s Table of Contents

        Copyright © 2018 ACM

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        Publication History

        • Published: 23 May 2018
        • Accepted: 1 December 2017
        • Revised: 1 November 2017
        • Received: 1 September 2016
        Published in toct Volume 10, Issue 2

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