We construct a formal framework for investigating epistemic and temporal notions in the context of distributed quantum computation. While we rely on structures developed earlier, we stress that our notion of quantum knowledge makes sense more generally in any agent-based model for distributed quantum systems. Several arguments are given to support our view that an agent's possibility relation should not be based on the reduced density matrix, but rather on local classical states and local quantum operations. In this way, we are able to analyse distributed primitives such as superdense coding and teleportation, obtaining interesting conclusions as to how the knowledge of individual agents evolves. We show explicitly that the knowledge transfer in teleportation is essentially classical, in that eventually, the receiving agent knows that its state is equal to the initial state of the sender. The relevant epistemic statements for teleportation deal with this correlation rather than with the actual quantum state, which is unknown throughout the protocol.
We construct a formal framework for investigating epistemic and temporal notions in the context of distributed quantum computation. While we rely on structures developed earlier, we stress that our notion of quantum knowledge makes sense more generally in any agent-based model for distributed quantum systems. Several arguments are given to support our view that an agent's possibility relation should not be based on the reduced density matrix, but rather on local classical states and local quantum operations. In this way, we are able to analyse distributed primitives such as superdense coding and teleportation, obtaining interesting conclusions as to how the knowledge of individual agents evolves. We show explicitly that the knowledge transfer in teleportation is essentially classical, in that eventually, the receiving agent knows that its state is equal to the initial state of the sender. The relevant epistemic statements for teleportation deal with this correlation rather than with the actual quantum state, which is unknown throughout the protocol.
This paper applies to quantum systems a modelling for the logic of knowledge, originally developed for reasoning about distributed systems, but since then applied to game theory, computer security and artificial intelligence. A formal model of quantum message passing systems is developed and the question of how one might define the semantics of a modal operator for knowledge in this model is considered. It is argued that there are at least two plausible semantics, depending on whether the agents are permitted to make use of their quantum state in determining what they know, and on whether one is dealing with single instances of quantum systems, or ensembles. The framework is illustrated using a number of examples from the quantum computing literature, including protocols for quantum key distribution and teleportation.
This paper applies to quantum systems a modelling for the logic of knowledge, originally developed for reasoning about distributed systems, but since then applied to game theory, computer security and artificial intelligence. A formal model of quantum message passing systems is developed and the question of how one might define the semantics of a modal operator for knowledge in this model is considered. It is argued that there are at least two plausible semantics, depending on whether the agents are permitted to make use of their quantum state in determining what they know, and on whether one is dealing with single instances of quantum systems, or ensembles. The framework is illustrated using a number of examples from the quantum computing literature, including protocols for quantum key distribution and teleportation.
This paper applies to quantum systems a modelling for the logic of knowledge, originally developed for reasoning about distributed systems, but since then applied to game theory, computer security and artificial intelligence. A formal model of quantum message passing systems is developed and the question of how one might define the semantics of a modal operator for knowledge in this model is considered. It is argued that there are at least two plausible semantics, depending on whether the agents are permitted to make use of their quantum state in determining what they know, and on whether one is dealing with single instances of quantum systems, or ensembles. The framework is illustrated using a number of examples from the quantum computing literature, including protocols for quantum key distribution and teleportation. 1
We develop a formal model for distributed measurement-based quantum computations, adopting an agent-based view, such that computations are described locally where possible. Because the network quantum state is in general entangled, we need to model it as a global structure, reminiscent of global memory in classical agent systems. Local quantum computations are described as measurement patterns. Since measurement-based quantum computation is inherently distributed, this allows us to extend naturally several concepts of the measurement calculus, a formal model for such computations. Our goal is to define an assembly language, i.e. we assume that computations are well-defined and we do not concern ourselves with verification techniques. The operational semantics for systems of agents is given by a probabilistic transition system, and we define operational equivalence in a way that it corresponds to the notion of bisimilarity. With this in place, we prove that teleportation is bisimilar to a direct quantum channel, and this also within the context of larger networks.
Abstract Quantum information gives rise to some puzzling epistemic problems that can be interestingly investigated from a logical point of view. A characteristic example is represented by teleportation phenomena, where knowledge and actions of observers (epistemic agents) play a relevant role. By abstracting from teleportation, we propose a simplified semantics for a language that consists of two parts: 1)the quantum computational sub-language, whose sentences α represent pieces of quantum information (which are supposed to be stored by some quantum systems)2)the classical epistemic sub-language, whose atomic sentences have the following forms: agent a has a probabilistic information about the sentence α; agent a knows the sentence α. Interestingly enough, some conceptual difficulties of standard epistemic logics can be avoided in this framework.
The Distributed Temporal Logic DTL allows one to reason about temporal properties of a distributed system from the local point of view of the system's agents, which are assumed to execute independently and to interact by means of event sharing. In this paper, we introduce the Quantum Branching Distributed Temporal Logic QBDTL, a variant of DTL able to represent quantum state transformations in an abstract, qualitative way. In QBDTL, each agent represents a distinct quantum bit (the unit of quantum information theory), which evolves by means of quantum transformations and possibly interacts with other agents, and n-ary quantum operators act as communication/synchronization points between agents. We endow QBDTL with a DTL-style semantics, which fits the intrinsically distributed nature of quantum computing, we formalize a labeled deduction system for QBDTL, and we prove the soundness and completeness of this deduction system with respect to the given semantics. We give a number of examples and, finally, we discuss possible extensions of our logic in order to reason about entangle-ment phenomena.