16,579 research outputs found
On the group theoretic structure of a class of quantum dialogue protocols
Intrinsic symmetry of the existing protocols of quantum dialogue are
explored. It is shown that if we have a set of mutually orthogonal -qubit
states {\normalsize
and a set of
() unitary operators
and
forms a group under multiplication then it
would be sufficient to construct a quantum dialogue protocol using this set of
quantum states and this group of unitary operators}. The sufficiency condition
is used to provide a generalized protocol of quantum dialogue. Further the
basic concepts of group theory and quantum mechanics are used here to
systematically generate several examples of possible groups of unitary
operators that may be used for implementation of quantum dialogue. A large
number of examples of quantum states that may be used to implement the
generalized quantum dialogue protocol using these groups of unitary operators
are also obtained. For example, it is shown that GHZ state, GHZ-like state, W
state, 4 and 5 qubit Cluster states, Omega state, Brown state, state
and state can be used for implementation of quantum dialogue protocol.
The security and efficiency of the proposed protocol is appropriately analyzed.
It is also shown that if a group of unitary operators and a set of mutually
orthogonal states are found to be suitable for quantum dialogue then they can
be used to provide solutions of socialist millionaire problem.Comment: 15 page
Robustness of Entanglement as a Resource
The robustness of multipartite entanglement of systems undergoing decoherence
is of central importance to the area of quantum information. Its
characterization depends however on the measure used to quantify entanglement
and on how one partitions the system. Here we show that the unambiguous
assessment of the robustness of multipartite entanglement is obtained by
considering the loss of functionality in terms of two communication tasks,
namely the splitting of information between many parties and the teleportation
of states.Comment: 11 pages, 5 figure
Spin characterization and control over the regime of radiation-induced zero-resistance states
Over the regime of the radiation-induced zero-resistance states and
associated oscillatory magnetoresistance, we propose a low magnetic field
analog of quantum-Hall-limit techniques for the electrical detection of
electron spin- and nuclear magnetic- resonance, dynamical nuclear polarization
via electron spin resonance, and electrical characterization of the nuclear
spin polarization via the Overhauser shift. In addition, beats observed in the
radiation-induced oscillatory-magnetoresistance are developed into a method to
measure and control the zero-field spin splitting due to the Bychkov-Rashba and
bulk inversion asymmetry terms in the high mobility GaAs/AlGaAs system.Comment: IEEE Transactions in Nanotechnology (to be published); 10 pages, 10
color figure
Dynamic generation of maximally entangled photon multiplets by adiabatic passage
The adiabatic passage scheme for quantum state synthesis, in which atomic
Zeeman coherences are mapped to photon states in an optical cavity, is extended
to the general case of two degenerate cavity modes with orthogonal
polarization. Analytical calculations of the dressed-state structure and Monte
Carlo wave-function simulations of the system dynamics show that, for a
suitably chosen cavity detuning, it is possible to generate states of photon
multiplets that are maximally entangled in polarization. These states display
nonclassical correlations of the type described by Greenberger, Horne, and
Zeilinger (GHZ). An experimental scheme to realize a GHZ measurement using
coincidence detection of the photons escaping from the cavity is proposed. The
correlations are found to originate in the dynamics of the adiabatic passage
and persist even if cavity decay and GHZ state synthesis compete on the same
time scale. Beyond entangled field states, it is also possible to generate
entanglement between photons and the atom by using a different atomic
transition and initial Zeeman state.Comment: 22 pages (RevTeX), including 23 postscript figures. To be published
in Physical Review
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