Measurement-device-independent quantum private queries by rotation-invariant twisted photons

Sijia Sun,Yuguang Yang,J Heled,A Yuan

doi:10.1051/matecconf/201817303024

Abstract

Quantum private query is an important cryptography protocol aiming to protect both user’s and database’s privacy. However, to execute even the simplest quantum private queries, one must establish and maintain a shared reference frame. Here we propose a rotation-invariant Measurement-device-independent quantum private queries with hybrid encoding approach, combined polarization and transverse spatial modes to overcome the polarization misalignment associated with random rotations in long-distance transmission. The initial encoding and final decoding of information in our protocol can be conveniently performed in the polarization space. Furthermore, our hybrid encoding approach only needs to insert four q-plates in practical experiment and to overcome the polarization misalignment problem.

Highlights

A symmetrically private information retrieval protocol (SPIR) [1] allows a user say Alice to retrieve an element of a database held by a database provider, Bob, but does not want him to learn anything about the item Alice is interested in
Classical solutions to the SPIR problem are generally based on some computational complexity theoretic assumption, which might be susceptible to the strong ability of quantum computation
Lo has proven that quantum mechanics alone cannot provide unconditionally secure perfect quantum oblivious transfer [4], this implies the impossibility of perfect quantum SPIR

Summary

Introduction

A symmetrically private information retrieval protocol (SPIR) [1] allows a user say Alice to retrieve an element of a database held by a database provider, Bob, but does not want him to learn anything about the item Alice is interested in. Lo has proven that quantum mechanics alone cannot provide unconditionally secure perfect quantum oblivious transfer [4], this implies the impossibility of perfect quantum SPIR It can be concluded from Lo’s proof that if a quantum SPIR has perfect user privacy, Alice can perform an attack to access the entire database without being detected. Though the GLM-protocol exhibit significant advantages in theory, it is difficult to implement because when large database is concerned the dimension of the oracle operation will be very high To solve this problem, Jakobi et al proposed an interesting strategy (J-protocol) [9]based on SARG04 protocol [10]. Practical QKD protocol proposed have in common the need for a shared reference frame between Alice and Bob, which requires the transmission of an infinite amount of information. This in turn means that encoding and decoding procedure in our protocol can be convenient performed in the polarization space, while the transmission is done in the rotation invariant hybrid space

Logical qubit encoding

Discussion

Database security

User security

Conclusions