Quantum online memory checking

  • Authors:
  • Wim van Dam;Qingqing Yuan

  • Affiliations:
  • Department of Computer Science, University of California, Santa Barbara;Department of Computer Science, University of California, Santa Barbara

  • Venue:
  • TQC'09 Proceedings of the 4th international conference on Theory of Quantum Computation, Communication, and Cryptography
  • Year:
  • 2009

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Abstract

The problem of memory checking considers storing files on an unreliable public server whose memory can be modified by a malicious party. The main task is to design an online memory checker with the capability to verify that the information on the server has not been corrupted. To store n bits of public information, the memory checker has s private reliable bits for verification purpose; while to retrieve each bit of public information the checker communicates t bits with the public memory. Earlier work showed that, for classical memory checkers, the lower bound s×t∈Ω(n) holds. In this article we study quantum memory checkers that have s private qubits and that are allowed to quantum query the public memory using t qubits. We prove an exponential improvement over the classical setting by showing the existence of a quantum checker that, using quantum fingerprints, requires only s∈O(logn) qubits of local memory and t∈O(polylog n) qubits of communication with the public memory.