19,228 research outputs found
Information Cascades on Arbitrary Topologies
In this paper, we study information cascades on graphs. In this setting, each
node in the graph represents a person. One after another, each person has to
take a decision based on a private signal as well as the decisions made by
earlier neighboring nodes. Such information cascades commonly occur in practice
and have been studied in complete graphs where everyone can overhear the
decisions of every other player. It is known that information cascades can be
fragile and based on very little information, and that they have a high
likelihood of being wrong.
Generalizing the problem to arbitrary graphs reveals interesting insights. In
particular, we show that in a random graph , for the right value of
, the number of nodes making a wrong decision is logarithmic in . That
is, in the limit for large , the fraction of players that make a wrong
decision tends to zero. This is intriguing because it contrasts to the two
natural corner cases: empty graph (everyone decides independently based on his
private signal) and complete graph (all decisions are heard by all nodes). In
both of these cases a constant fraction of nodes make a wrong decision in
expectation. Thus, our result shows that while both too little and too much
information sharing causes nodes to take wrong decisions, for exactly the right
amount of information sharing, asymptotically everyone can be right. We further
show that this result in random graphs is asymptotically optimal for any
topology, even if nodes follow a globally optimal algorithmic strategy. Based
on the analysis of random graphs, we explore how topology impacts global
performance and construct an optimal deterministic topology among layer graphs
Quantum information processing architecture with endohedral fullerenes in a carbon nanotube
A potential quantum information processor is proposed using a fullerene
peapod, i.e., an array of the endohedral fullerenes 15N@C60 or 31P@C60
contained in a single walled carbon nanotube (SWCNT). The qubits are encoded in
the nuclear spins of the doped atoms, while the electronic spins are used for
initialization and readout, as well as for two-qubit operations.Comment: 8 pages, 8 figure
One-step implementation of multi-qubit conditional phase gating with nitrogen-vacancy centers coupled to a high-Q silica microsphere cavity
The diamond nitrogen-vacancy (NV) center is an excellent candidate for
quantum information processing, whereas entangling separate NV centers is still
of great experimental challenge. We propose an one-step conditional phase flip
with three NV centers coupled to a whispering-gallery mode cavity by virtue of
the Raman transition and smart qubit encoding. As decoherence is much
suppressed, our scheme could work for more qubits. The experimental feasibility
is justified.Comment: 3 pages, 2 figures, Accepted by Appl. Phys. Let
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