3,624 research outputs found
Enhanced No-Go Theorem for Quantum Position Verification
Based on the instantaneous nonlocal quantum computation (INQC), Buhrman et
al. proposed an excellent attack strategy to quantum position verification
(QPV) protocols in 2011, and showed that, if the colluding adversaries are
allowed to previously share unlimited entangled states, it is impossible to
design an unconditionally secure QPV protocol in the previous model. Here,
trying to overcome this no-go theorem, we find some assumptions in the INQC
attack, which are implicit but essential for the success of this attack, and
present three different QPV protocols where these assumptions are not
satisfied. We show that for the general adversaries, who execute the attack
operations at every common time slot or the time when they detect the arrival
of the challenge signals from the verifiers, secure QPV is achievable. This
implies practically secure QPV can be obtained even if the adversaries is
allowed to share unlimited entanglement previously. Here by "practically" we
mean that in a successful attack the adversaries need launch a new round of
attack on the coming qubits with extremely high frequency so that none of the
possible qubits, which may be sent at random time, will be missed. On the other
side, using such Superdense INQC (SINQC) attack, the adversaries can still
attack the proposed protocols successfully in theory. The particular attack
strategies to our protocols are presented respectively. On this basis, we
demonstrate the impossibility of secure QPV with looser assumptions, i.e. the
enhanced no-go theorem for QPV.Comment: 19 pages, single column, 3 tables, 6 figure
Cryptanalysis of a multi-party quantum key agreement protocol with single particles
Recently, Sun et al. [Quant Inf Proc DOI: 10.1007/s11128-013-0569-x]
presented an efficient multi-party quantum key agreement (QKA) protocol by
employing single particles and unitary operations. The aim of this protocol is
to fairly and securely negotiate a secret session key among parties with a
high qubit efficiency. In addition, the authors claimed that no participant can
learn anything more than his/her prescribed output in this protocol, i.e., the
sub-secret keys of the participants can be kept secret during the protocol.
However, here we points out that the sub-secret of a participant in Sun et
al.'s protocol can be eavesdropped by the two participants next to him/her. In
addition, a certain number of dishonest participants can fully determine the
final shared key in this protocol. Finally, we discuss the factors that should
be considered when designing a really fair and secure QKA protocol.Comment: 7 page
The Oblique Corrections from Heavy Scalars in Irreducible Representations
The contributions to , , and from heavy scalars in any irreducible
representation of the electroweak gauge group are
obtained. We find that in the case of a heavy scalar doublet there is a slight
difference between the parameter we have obtained and that in previous
works.Comment: 6 pages, 2 axodraw figures; minor changes, references update
Identifying vital edges in Chinese air route network via memetic algorithm
Due to its rapid development in the past decade, air transportation system
has attracted considerable research attention from diverse communities. While
most of the previous studies focused on airline networks, here we
systematically explore the robustness of the Chinese air route network, and
identify the vital edges which form the backbone of Chinese air transportation
system. Specifically, we employ a memetic algorithm to minimize the network
robustness after removing certain edges hence the solution of this model is the
set of vital edges. Counterintuitively, our results show that the most vital
edges are not necessarily the edges of highest topological importance, for
which we provide an extensive explanation from the microscope of view. Our
findings also offer new insights to understanding and optimizing other
real-world network systems
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