1,075 research outputs found
Reliable entanglement transfer between pure quantum states
The problem of the reliable transfer of entanglement from one pure bipartite
quantum state to another using local operations is analyzed. It is shown that
in the case of qubits the amount that can be transferred is restricted to the
difference between the entanglement of the two states. In the presence of a
catalytic state the range of the transferrable amount broadens to a certain
degree.Comment: 6 pages, 4 pictures; revised version; to appear in Phys. Rev.
Tavis-Cummings model and collective multi-qubit entanglement in trapped ions
We present a method of generating collective multi-qubit entanglement via
global addressing of an ion chain following the guidelines of the
Tavis-Cummings model, where several qubits are coupled to a collective motional
mode. We show that a wide family of Dicke states and irradiant states can be
generated by single global laser pulses, unitarily or helped with suitable
postselection techniques.Comment: 6 pages, 3 figures. Accepted for publication in Physical Review
Production of \phi Mesons in Near-Threshold \pi N and N N Reactions
We analyze the production of mesons in and NN reactions in the
near-threshold region, using throughout the conventional ``non-strange''
dynamics based on such processes which are allowed by the non-ideal
mixing. We show that the occurrence of the direct
interaction may show up in different unpolarized and polarization observables
in reactions. We find a strong non-trivial difference between
observables in the reactions and caused by the
different role of the spin singlet and triplet states in the entrance channel.
A series of predictions for the experimental study of this effect is presented.Comment: 35 pages including 18 figure
A classical analog to topological non-local quantum interference effect
The two main features of the Aharonov-Bohm effect are the topological
dependence of accumulated phase on the winding number around the magnetic
fluxon, and non-locality -- local observations at any intermediate point along
the trajectories are not affected by the fluxon. The latter property is usually
regarded as exclusive to quantum mechanics. Here we show that both the
topological and non-local features of the Aharonov-Bohm effect can be
manifested in a classical model that incorporates random noise. The model also
suggests new types of multi-particle topological non-local effects which have
no quantum analog.Comment: 4 pages, to be published in Phys. Rev. Let
A probabilistic and information theoretic interpretation of quantum evolutions
In quantum mechanics, outcomes of measurements on a state have a
probabilistic interpretation while the evolution of the state is treated
deterministically. Here we show that one can also treat the evolution as being
probabilistic in nature and one can measure `which unitary' happened. Likewise,
one can give an information-theoretic interpretation to evolutions by defining
the entropy of a completely positive map. This entropy gives the rate at which
the informational content of the evolution can be compressed. One cannot
compress this information and still have the evolution act on an unknown state,
but we demonstrate a general scheme to do so probabilistically. This allows one
to generalize super-dense coding to the sending of quantum information. One can
also define the ``interaction-entanglement'' of a unitary, and concentrate this
entanglement.Comment: 9 page
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