31,139 research outputs found
Entanglement of spin waves among four quantum memories
Quantum networks are composed of quantum nodes that interact coherently by
way of quantum channels and open a broad frontier of scientific opportunities.
For example, a quantum network can serve as a `web' for connecting quantum
processors for computation and communication, as well as a `simulator' for
enabling investigations of quantum critical phenomena arising from interactions
among the nodes mediated by the channels. The physical realization of quantum
networks generically requires dynamical systems capable of generating and
storing entangled states among multiple quantum memories, and of efficiently
transferring stored entanglement into quantum channels for distribution across
the network. While such capabilities have been demonstrated for diverse
bipartite systems (i.e., N=2 quantum systems), entangled states with N > 2 have
heretofore not been achieved for quantum interconnects that coherently `clock'
multipartite entanglement stored in quantum memories to quantum channels. Here,
we demonstrate high-fidelity measurement-induced entanglement stored in four
atomic memories; user-controlled, coherent transfer of atomic entanglement to
four photonic quantum channels; and the characterization of the full
quadripartite entanglement by way of quantum uncertainty relations. Our work
thereby provides an important tool for the distribution of multipartite
entanglement across quantum networks.Comment: 4 figure
The Quantum Internet
Quantum networks offer a unifying set of opportunities and challenges across
exciting intellectual and technical frontiers, including for quantum
computation, communication, and metrology. The realization of quantum networks
composed of many nodes and channels requires new scientific capabilities for
the generation and characterization of quantum coherence and entanglement.
Fundamental to this endeavor are quantum interconnects that convert quantum
states from one physical system to those of another in a reversible fashion.
Such quantum connectivity for networks can be achieved by optical interactions
of single photons and atoms, thereby enabling entanglement distribution and
quantum teleportation between nodes.Comment: 15 pages, 6 figures Higher resolution versions of the figures can be
downloaded from the following link:
http://www.its.caltech.edu/~hjkimble/QNet-figures-high-resolutio
Measuring quantumness: from theory to observability in interferometric setups
We investigate the notion of quantumness based on the non-commutativity of
the algebra of observables and introduce a measure of quantumness based on the
mutual incompatibility of quantum states. We show that such a quantity can be
experimentally measured with an interferometric setup and that, when an
arbitrary bipartition of a given composite system is introduced, it detects the
one-way quantum correlations restricted to one of the two subsystems. We
finally show that, by combining only two projective measurements and carrying
out the interference procedure, our measure becomes an efficient universal
witness of quantum discord and non-classical correlations.Comment: 5 pages, 1 figur
Energy efficient mining on a quantum-enabled blockchain using light
We outline a quantum-enabled blockchain architecture based on a consortium of
quantum servers. The network is hybridised, utilising digital systems for
sharing and processing classical information combined with a fibre--optic
infrastructure and quantum devices for transmitting and processing quantum
information. We deliver an energy efficient interactive mining protocol enacted
between clients and servers which uses quantum information encoded in light and
removes the need for trust in network infrastructure. Instead, clients on the
network need only trust the transparent network code, and that their devices
adhere to the rules of quantum physics. To demonstrate the energy efficiency of
the mining protocol, we elaborate upon the results of two previous experiments
(one performed over 1km of optical fibre) as applied to this work. Finally, we
address some key vulnerabilities, explore open questions, and observe
forward--compatibility with the quantum internet and quantum computing
technologies.Comment: 25 pages, 5 figure
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