1,011 research outputs found
Deterministic Quantum Dense Coding Networks
We consider the scenario of deterministic classical information transmission
between multiple senders and a single receiver, when they a priori share a
multipartite quantum state -- an attempt towards building a deterministic dense
coding network. Specifically, we prove that in the case of two or three senders
and a single receiver, generalized Greenberger-Horne-Zeilinger (gGHZ) states
are not beneficial for sending classical information deterministically beyond
the classical limit, except when the shared state is the GHZ state itself. On
the other hand, three- and four-qubit generalized W (gW) states with specific
parameters as well as the four-qubit Dicke states can provide a quantum
advantage of sending the information in deterministic dense coding.
Interestingly however, numerical simulations in the three-qubit scenario reveal
that the percentage of states from the GHZ-class that are deterministic dense
codeable is higher than that of states from the W-class.Comment: 11 pages, 2 figures, close to published versio
Probabilistic instantaneous quantum computation
The principle of teleportation can be used to perform a quantum computation
even before its quantum input is defined. The basic idea is to perform the
quantum computation at some earlier time with qubits which are part of an
entangled state. At a later time a generalized Bell state measurement is
performed jointly on the then defined actual input qubits and the rest of the
entangled state. This projects the output state onto the correct one with a
certain exponentially small probability. The sufficient conditions are found
under which the scheme is of benefit.Comment: 4 pages, 1 figur
Optimal finite measurements and Gauss quadratures
We exhibit measurements for optimal state estimation which have a finite
number of outcomes. This is achieved by a connection between finite optimal
measurements and Gauss quadratures. The example we consider to illustrate this
connection is that of state estimation on qubits, all in a same pure state.
Extensions to state estimation of mixed states are also discussed.Comment: 7 pages, 2 figures, paragraph added at the end of the article
(extension of the problem to general states
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