We initiate the study of asynchronous quantum distributed systems, focusing on the case of implementing atomic quantum global operations that can be decomposed into a collection of local operations on the components of the system. A simple example of such an operation is a quantum snapshot in which the whole system is instantaneously measured. Based on the classical snapshot algorithm of Chandy and Lamport, we design a quantum distributed algorithm to implement such decomposable global operations, which we call the QGO Algorithm. The analysis of our algorithm shows that arguments based on Lamport's computational causality remain valid in the quantum world, even though, due to entanglement, causality is not manifest from the standard description of the system in terms of a (global) quantum state. Our other contributions include a formal model of quantum distributed computing, and a formal specification for the desired behavior of a global operation, which may be of interest even in classical settings (such as in the setting of randomized algorithms).

翻译：我们开启了异步量子分布式系统的研究，着重于实现可分解为系统组件上局部操作集合的原子量子全局操作。这类操作的一个简单示例是量子快照，其中整个系统被瞬时测量。基于Chandy和Lamport的经典快照算法，我们设计了一种量子分布式算法来实现此类可分解的全局操作，称之为QGO算法。对该算法的分析表明，基于Lamport计算因果性的论证在量子世界中仍然有效，尽管由于纠缠，因果性在从（全局）量子态对系统的标准描述中并不显式体现。我们的其他贡献包括一个量子分布式计算的形式化模型，以及全局操作期望行为的形式化规范——即便在经典设置中（例如随机化算法的设置），这一规范也可能具有意义。