W-state Analyzer and Multi-party Measurement-device-independent Quantum Key Distribution

Changhua Zhu, Feihu Xu, Changxing Pei
2015 Scientific Reports  
W-state is an important resource for many quantum information processing tasks. In this paper, we for the first time propose a multi-party measurement-device-independent quantum key distribution (MDI-QKD) protocol based on W-state. With linear optics, we design a W-state analyzer in order to distinguish the four-qubit W-state. This analyzer constructs the measurement device for four-party MDI-QKD. Moreover, we derived a complete security proof of the four-party MDI-QKD, and performed a
more » ... simulation to study its performance. The results show that four-party MDI-QKD is feasible over 150 km standard telecom fiber with off-the-shelf single photon detectors. This work takes an important step towards multi-party quantum communication and a quantum network. The quantum key distribution (QKD) protocol, which is based on the principles of quantum mechanism, is unconditionally secure in theory 1,2 . For a review, see, e.g. Ref. 3. In practice, however, a QKD system still has security loopholes due to the gap between theory and practice. Various attacks have been successfully launched through the exploration of these loopholes, e.g. a time-shift attack 4,5 , a phase-remapping attack 6 , a blinding attack 7,8 , and so forth 9-11 . To close this gap, the first method is to build precise mathematical models for all the devices and refine the security proofs to include these models 12 . However, this method is challenging to implement due to the complexity of QKD components. In addition, a device-independent QKD (DI-QKD) was proposed 13,14 . In DI-QKD, the legitimate participants during the process of communication, namely, Alice and Bob, do not need to obtain precise mathematical models for their devices, and all side-channels can be removed from QKD implementations if certain requirements can be satisfied. However, the implementation requires a loophole-free Bell test, which is still out the scope of current technology. Instead, a new protocol, measurement-device-independent QKD (MDI-QKD) 15 (for a review, see ref. 16), was proposed. This protocol is fully practicable with current technology. Unlike security patches 17,18 , MDI-QKD can remove all detector side-channel attacks. This kind of attack is arguably the most important security loophole in conventional QKD implementations [7] [8] [9] [10] [11] 19 . The measurement setup in MDI-QKD can be fully untrusted and even manufactured by Eve. The experimental feasibility of MDI-QKD has been demonstrated in both the laboratory and field tests 20-23 . MDI-QKD has also attracted a lot of scientific attention from theoretical side 24-31 . In addition to the application in QKD, MDI technique can also be used in other quantum information processing tasks, such as MDI entanglement-witness 32 . In addition to the two-party QKD protocol, researchers have also proposed various multi-party QKD protocols. Generally, there are three types of multi-party QKD schemes. The first one is based on a trusted center (TC) 33 , in which each user shares a secret key with the TC and builds a common session key. The second one is an entanglement-based multi-party QKD protocol. Cabello proposed a multi-party QKD protocol that uses Greenberger-Horne-Zeilinger (GHZ) states 34 and that is an extension of a two-party entanglement-based QKD protocol 2 . Chen and Lo proposed a wide class of distillation schemes for multi-party entanglement, which have been applied to implement conference key agreement 35, 36 . The third one is a multi-party QKD protocol without the use of entanglement and TC. Matsumoto proposed a QKD protocol in which Alice sends the same qubits sequence to Bob and Charlie respectively, and the qubits with coincident bases are used to build a secret key after post-processing 37 . In the first type of scheme, information may be leaked since pre-shared secret bits are used repeatedly. In the second type, a perfect GHZ state should be prepared. In the third type, two prepare-and-measure QKD processes are implemented. Nevertheless, up until now, a key weakness of all multi-party quantum cryptographic protocols is
doi:10.1038/srep17449 pmid:26644289 pmcid:PMC4672340 fatcat:xttbyd5l4napvl3zl7qzpfbkjy