Quantum Clock Synchronization In Multiparty Relativistic Quantum System

The emerging field of relativistic quantum information combines general relativity,quantum information,quantum optics and quantum mechanics.It is further explored in non-inertial systems and in curved spacetime.It not only discusses the quantum information problem,but also promotes the solution of the black hole entropy and other difficult problems.In this paper,multi-body quantum entanglement,quantum clock synchronization and other problems are studied systematically.We mainly completed the following aspects of work:The multiparty quantum system modeled by Unruh-DeWitt detectors where one of atoms has been accelerated is studied.Each Unruh-DeWitt detector is composed of a two-level non-interacting atom.We consider the evolution of entire multiparty quantum entangled system with a symmetric multiparty state-Z state as the initial state.The Z state we choosing is assumed to have k atoms lie in the excited state in the n-party system and n-k atoms be in the ground state,where k can take any integer from 1 to n.Compared to another symmetric form of the multiparty state,known as W-state,where only one atom is presented in the excited state and the remaining atoms are in the ground state,Z state is more general.And then we give the final state of a multiparty system in which any one atom performs accelerated motion and interacts with the surrounding field.With quantum metrology,we estimate Unruh temperature and interaction between the accelerated atom and the scalar field of our relativistic multiparty quantum system.We find: a)With the more total atoms n and the less excited atoms k in multiparty system,the precision for estimating Unruh temperature is higher.That's to say,multiparty system is better than two-party system,and W-type initial state performs better than Ztype initial state when we estimate Unruh temperature.b)Different from the estimation of Unruh temperature,multiparty system must modeled by less total atoms n and more excited atoms k when we want to obtain the higher precision of estimating the effective coupling.This paper also studies the clock synchronization for the accelerated atomic clock in the multiparty system.Since one of the detectors experiences the accelerated motion and the rest detectors remain static,we need to consider the relativistic effect caused by time delay of the accelerated clock,and its synchronization with the rest static clocks.We use a set of dual measurement basis firstly for the standard clock,choosen from the static clocks,and then for the accelerated clock.We end up with a time probability that implies the time difference information.With this observable time probability,we can figure out the time difference between two clocks We analyzed influences of the initial state and the accelerated motion on the time probability we obtain.We find: a)The accelerated motion and the interaction between the atom and a scalar field would effect on us to select the optimal multiparty state and obtain the most clock adjustment accuracy for the time difference;b)The entanglement between the accelerated clock and the standard clock enhances the clock adjustment accuracy of quantum clock synchronization;c)In other similar cases,quantum clock synchronization with the two-party system always owns more clock adjustment accuracy than that of multiparty system.Finally,we estimate the time difference of multiparty quantum clock synchronization.We find: a)For a multiparty system with a certain size n,we could choose the proper excited atoms k to maximal the accuracy of estimating the time difference;b)When the acceleration a ? 1 and the effective coupling parameter ? ? 0.1,both lead to the sharp drop of accuracy for estimating the time diiference.