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arXiv:1411.3186 · Physical Review A

Operation-triggered quantum clock synchronization

Jie-Dong Yue, Yu-Ran Zhang, Heng Fan

Published Sep 21, 2015• 10 citations
arXivHTMLPDF

Abstract

We present a quantum clock synchronization scheme of multiple parties which uses operation as the trigger to start the evolution of the initial state. In comparison, the existing protocols use measurement to start the evolution. We show that our protocol links the problem to a multiple-phase estimation problem, such that we have provided a general framework for the study of quantum clock synchronization. We can use the Fisher information to give the precision of the synchronization, and we explicitly show that the Heisenberg scale of synchronization is achieved in the two-party case. We prove that the measurement-triggered quantum clock synchronization is included in the operation-triggered quantum clock synchronization, so the operation-triggered quantum clock synchronization is, in general, more powerful than measurement-triggered quantum clock synchronization. We show that our protocol is very efficient in synchronizing a clock to the average time of other clocks.

DOI
10.1103/physreva.92.032321

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We present a quantum clock synchronization scheme of multiple parties which uses operation as the trigger to start the evolution of the initial state. In comparison, the existing protocols use measurement to start the evolution. We show that our protocol links the problem to a multiple-phase estimation problem, such that we have provided a general framework for the study of quantum clock synchronization. We can use the Fisher information to give the precision of the synchronization, and we explicitly show that the Heisenberg scale of synchronization is achieved in the two-party case. We prove that the measurement-triggered quantum clock synchronization is included in the operation-triggered quantum clock synchronization, so the operation-triggered quantum clock synchronization is, in general, more powerful than measurement-triggered quantum clock synchronization. We show that our protocol is very efficient in synchronizing a clock to the average time of other clocks.
Industrial networks are frequently utilized for safety-critical applications that demand real-time requirements. Message scheduling or timestamp is typically a key component of such applications, which are typically time-triggered. Timestamps at each party in quantum communication must be synchronized or share a common understanding of time for secure communication. Clock synchronization is thus a key component of real-time networks. Despite the benefits of time synchronization, enforcing clock synchronization on behalf of several quantum channel parties and preventing attacks from an adversary is still tricky. This paper identifies a possible attack on time synchronization and a way to solve the aforementioned issues. Therefore, we need a protocol that establishes a secure environment in terms of security with time synchronization so that various parties may freely and openly communicate. This paper also addresses significant research gaps in time synchronization and how it might be realized and applied to quantum communication. These include recommendations for new directions to be taken based on existing protocols.
We propose a multiparty quantum clock synchronization protocol that makes optimal use of the maximal multipartite entanglement of GHZ-type states. To realize the protocol, different versions of maximally entangled eigenstates of collective energy are generated by local transformations that distinguish among different groupings of the parties. The maximal sensitivity of the entangled states to time differences between the local clocks can then be accessed if all parties share the results of their local time-dependent measurements. The efficiency of the protocol is evaluated in terms of the statistical errors in the estimation of time differences and the performance of the protocol is compared to alternative protocols proposed previously.
Abstract A major outstanding problem for many quantum clock synchronization protocols is the hidden assumption of a common phase reference between the parties to be synchronized. In general, the definition of the quantum states between two parties do not have consistent phase definitions, which can lead to an unknown systematic error. We show that despite prior arguments to the contrary, it is possible to remove this unknown phase via entanglement purification. This closes the loophole for entanglement based quantum clock synchronization protocols, which is a non-local approach to synchronize two clocks independent of the properties of the intervening medium. Starting with noisy Bell pairs, we show that the scheme produces a singlet state for any combination of (i) differing basis conventions for Alice and Bob; (ii) an overall time offset in the execution of the purification algorithm; and (iii) the presence of a noisy channel. Error estimates reveal that better performance than existing classical Einstein synchronization protocols should be achievable using current technology.
The ability to synchronize remote clocks plays an increasingly important role in our infrastructure, from maintaining coherence in the electrical grid to allowing precise positioning and navigation for civilian and military applications. However, many of the techniques to establish and maintain this time synchronization have been shown to be susceptible to interference by malicious parties. Here we propose a protocol that builds on techniques from quantum communication to provide a verified and secure time synchronization protocol. In contrast with classical protocols aimed at increasing the security of time distribution, we need not make any assumptions about the distance or propagation times between the clocks. In order to compromise the security of the protocol, an adversary must be able to perform quantum non-demolition measurements of the presence of a singe photon with high probability. The requirement of such quantum measurements raises a serious technological barrier for any would-be adversary
Abstract This paper investigates multipartite quantum clock synchronization (QCS) procedures using a new class of quantum states called collective symmetric (CS) states, which generalize Dicke and N00N-type states. Among all the QCS techniques proposed in the literature, the focus here is on procedures relying on local operations and classical communication (LOCC). Two synchronization scenarios that are particularly useful for quantum networks are considered: (i) pair synchronization where multiple arbitrarily chosen disjoint pairs of nodes aim to align their clocks, and (ii) network synchronization where all nodes aim to synchronize their clocks to a common average time. First, the paper discusses the use of CS states in QCS procedures previously proposed in the literature for both scenarios. Second, possible limitations of the QCS procedures are considered in terms of insufficient robustness and estimation ambiguity. Third, a new procedure, referred to as efficient synchronization procedure (ESP), is designed for each of the two synchronization scenarios. The ESP is shown to address the aforementioned limitations and to outperform the state-of-the-art LOCC-based multipartite QCS procedures in terms of synchronization precision.