title: Quantum clock synchronization with a single qudit.
abstract: Clock synchronization for nonfaulty processes in multiprocess networks is indispensable for a variety of technologies. A reliable system must be able to resynchronize the nonfaulty processes upon some components failing causing the distribution of incorrect or conflicting information in the network. The task of synchronizing such networks is related to Byzantine agreement (BA), which can classically be solved using recursive algorithms if and only if less than one-third of the processes are faulty. Here we introduce a nonrecursive quantum algorithm, based on a quantum solution of the detectable BA, which achieves clock synchronization in the presence of arbitrary many faulty processes by using only a single quantum system.
authors.affiliation: Physics Department, Stockholm University, S-10691, Stockholm, Sweden.
authors.forename: Armin
authors.initials: A
authors.lastname: Tavakoli
authors.affiliation: Departamento de Física Aplicada II, Universidad de Sevilla, E-41012 Sevilla, Spain.
authors.forename: Adán
authors.initials: A
authors.lastname: Cabello
authors.affiliation: Instytut Fizyki Teoretycznej i Astrofizyki, Uniwersytet Gdański, PL-80-952 Gdańsk, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Żukowski
authors.affiliation: Physics Department, Stockholm University, S-10691, Stockholm, Sweden.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bourennane