693 research outputs found
Recursive quantum repeater networks
Internet-scale quantum repeater networks will be heterogeneous in physical
technology, repeater functionality, and management. The classical control
necessary to use the network will therefore face similar issues as Internet
data transmission. Many scalability and management problems that arose during
the development of the Internet might have been solved in a more uniform
fashion, improving flexibility and reducing redundant engineering effort.
Quantum repeater network development is currently at the stage where we risk
similar duplication when separate systems are combined. We propose a unifying
framework that can be used with all existing repeater designs. We introduce the
notion of a Quantum Recursive Network Architecture, developed from the emerging
classical concept of 'recursive networks', extending recursive mechanisms from
a focus on data forwarding to a more general distributed computing request
framework. Recursion abstracts independent transit networks as single relay
nodes, unifies software layering, and virtualizes the addresses of resources to
improve information hiding and resource management. Our architecture is useful
for building arbitrary distributed states, including fundamental distributed
states such as Bell pairs and GHZ, W, and cluster states.Comment: 14 page
Quantum Repeaters using Coherent-State Communication
We investigate quantum repeater protocols based upon atomic
qubit-entanglement distribution through optical coherent-state communication.
Various measurement schemes for an optical mode entangled with two spatially
separated atomic qubits are considered in order to nonlocally prepare
conditional two-qubit entangled states. In particular, generalized measurements
for unambiguous state discrimination enable one to completely eliminate
spin-flip errors in the resulting qubit states, as they would occur in a
homodyne-based scheme due to the finite overlap of the optical states in phase
space. As a result, by using weaker coherent states, high initial fidelities
can still be achieved for larger repeater spacing, at the expense of lower
entanglement generation rates. In this regime, the coherent-state-based
protocols start resembling single-photon-based repeater schemes.Comment: 11 pages, 8 figure
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