Fast Quantum Byzantine Agreement: Difference between revisions

Fast Quantum Byzantine Agreement (edit)

Revision as of 04:58, 18 April 2019

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 '''Tags:''' [[:Category: Quantum Enhanced Classical Functionality|Quantum Enhanced Classical Functionality]][[Category: Quantum Enhanced Classical Functionality]], [[:Category: Multi Party Protocols|Multi Party Protocols]] [[Category: Multi Party Protocols]],  [[:Category:Specific Task|Specific Task]][[Category:Specific Task]], consensus task, failure resistant distributed computing
 ==Assumptions==
-* We assume that the original input qubit is unknown and the protocol is independent of the original input state (universality).
+* '''Network:''' The network consists of <math>n</math> players that are fully identified and [[completely connected]] with pairwise [[authenticated]] classical and quantum channels.
-* The output copies are not identical and we are able to control the likelihood (fidelity) of the output copies to the original state by pre-preparing the ancillary states with special coefficients.
+* '''Timing:''' [[Synchronous]] and [[asynchronous]] setting are both considered.
+* '''Message size:''' The size of messages (quantum and classical) are unbounded.
+* '''Shared resources:''' The nodes do not share any prior entanglement or classical correlations.
+* '''Failure:''' At most <math>t < n/3</math> (synchronous) or <math>t < n/4</math> (asynchronous) Byzantine node failures are assumed. Byzantine failures are allowed to behave arbitrarily and collude to try and prevent the honest players from reaching agreement. The most severe model is used: Byzantine failures are [[adaptive]], [[computationally unbounded]] and have [[full-information]] (full information of quantum states is modeled by giving a classical description of the state to the adversaries). [[Link failures]] are not considered.
 ==Outline==
 In this protocol, there are three main stages. The first stage is a preparation stage. we prepare two ancillary states with special coefficients which will lead to the desired flow of the information between copied states. The original state will not be engaged at this stage. At the second stage the cloner circuit will act on all the three states (the original and two other states) and at the second stage the two copied state will appear at two of the outputs and one of the outputs should be discarded. The Procedure will be as following: