57 research outputs found
Reply to Marinatto's comment on "Bell's theorem without inequalities and without alignments"
Marinatto claims that in the proof of Bell's theorem without inequalities and
without alignments [A. Cabello, Phys. Rev. Lett. 91, 230403 (2003)], local
observables cannot be measured by means of tests on individual qubits.
Marinatto's claim is incorrect. To support this, the proof is explicitly
rewritten in terms of tests on individual qubits.Comment: REVTeX4, 1 pag
Reply to Marinatto's comment on "Bell's theorem without inequalities and without probabilities for two observers"
It is shown that Marinatto's claim [Phys. Rev. Lett. 90, 258901 (2003)] that
the proof of "Bell's theorem without inequalities and without probabilities for
two observers" [A. Cabello, Phys. Rev. Lett. 86, 1911 (2001)] requires four
spacelike separated observers rather than two is unjustified.Comment: REVTeX4, 1 pag
Backwards-induction outcome in a quantum game
In economics duopoly is a market dominated by two firms large enough to
influence the market price. Stackelberg presented a dynamic form of duopoly
that is also called `leader-follower' model. We give a quantum perspective on
Stackelberg duopoly that gives a backwards-induction outcome same as the Nash
equilibrium in static form of duopoly also known as Cournot's duopoly. We find
two qubit quantum pure states required for this purpose.Comment: Revised in the light of referee's comments. Latex, 16 pages, 2
figures, To appear in Phy. Rev.
p-Branes Electric-Magnetic Duality and Stueckelberg/Higgs Mechanism: a Path-Integral Approach
We study the vacuum functional for a system of p-branes interacting with
Maxwell fields of higher rank. This system represents a generalization of the
usual electrodynamics of point particles, with one essential difference:
namely, that the world-history of a p-brane, due to the spatial extension of
the object, may possess a physical boundary. Thus, the objective of this study
is twofold: first, we wish to exploit the breaking of gauge invariance due to
the presence of a physical boundary, in order to generate mass as an
alternative to the Higgs mechanism; second, we wish to investigate how the new
mechanism of mass generation is affected by the duality transformation between
electric and magnetic branes. The whole analysis is performed by using the
path-integral method, as opposed to the more conventional canonical approach.
The advantage of the path integral formulation is that it enables us to Fourier
transform the field strength directly, rather than the gauge potential. To our
knowledge, this field strength formulation represents a new application of the
path integral method, and leads, in a straightforward way, to the dual
representation of the vacuum functional. We find that the effect of the dual
transformation is essentially that of exchanging the role of the gauge fields
defined respectively on the " bulk'' and "boundary" of the p-brane history.Comment: 17pages, Revtex, no figures. Added refrences. To appear in
Progr.Th.Phy
General criterion for the entanglement of two indistinguishable particles
We relate the notion of entanglement for quantum systems composed of two
identical constituents to the impossibility of attributing a complete set of
properties to both particles. This implies definite constraints on the
mathematical form of the state vector associated with the whole system. We then
analyze separately the cases of fermion and boson systems, and we show how the
consideration of both the Slater-Schmidt number of the fermionic and bosonic
analog of the Schmidt decomposition of the global state vector and the von
Neumann entropy of the one-particle reduced density operators can supply us
with a consistent criterion for detecting entanglement. In particular, the
consideration of the von Neumann entropy is particularly useful in deciding
whether the correlations of the considered states are simply due to the
indistinguishability of the particles involved or are a genuine manifestation
of the entanglement. The treatment leads to a full clarification of the subtle
aspects of entanglement of two identical constituents which have been a source
of embarrassment and of serious misunderstandings in the recent literature.Comment: 18 pages, Latex; revised version: Section 3.2 rewritten, new Theorems
added, reference [1] corrected. To appear on Phys.Rev.A 70, (2004
Quantum mechanics gives stability to a Nash equilibrium
We consider a slightly modified version of the Rock-Scissors-Paper (RSP) game
from the point of view of evolutionary stability. In its classical version the
game has a mixed Nash equilibrium (NE) not stable against mutants. We find a
quantized version of the RSP game for which the classical mixed NE becomes
stable.Comment: Revised on referee's criticism, submitted to Physical Review
Dilemma and Quantum Battle of Sexes
We analysed quantum version of the game battle of sexes using a general
initial quantum state. For a particular choice of initial entangled quantum
state it is shown that the classical dilemma of the battle of sexes can be
resolved and a unique solution of the game can be obtained.Comment: Revised, Latex, 9 pages, no figure, corresponding author's email:
[email protected]
Playing a quantum game with a corrupted source
The quantum advantage arising in a simplified multi-player quantum game, is
found to be a disadvantage when the game's qubit-source is corrupted by a noisy
"demon". Above a critical value of the corruption-rate, or noise-level, the
coherent quantum effects impede the players to such an extent that the optimal
choice of game changes from quantum to classical.Comment: This version will appear in PRA (Rapid Comm.
- …