2,462 research outputs found
Cross-Kerr interaction in a four-level atomic system
We derive the form of the cross-Kerr interaction in a four-level atomic
system in the N-configuration. We use time-independent perturbation theory to
calculate the eigenenergies and eigenstates of the Schrodinger equation for the
system. The system is considered as a perturbation of a Raman resonant
three-level lambda scheme for which exact solutions are known. We show that
within the strong control field limit the cross-Kerr interaction can arise
between two weak probe fields. The strength of this nonlinear coupling is
several orders of magnitude larger than that achievable using optical fibres.Comment: 5 pages, resubmitted to Physical Review A with clarified style and
correction to Fig
Generation of continuous variable Einstein-Podolsky-Rosen entanglement via the Kerr nonlinearity in an optical fiber
We report on the generation of a continuous variable Einstein-Podolsky-Rosen (EPR) entanglement using an optical fiber interferometer. The Kerr nonlinearity in the fiber is exploited for the generation of two independent squeezed beams. These interfere at a beam splitter and EPR entanglement is obtained between the output beams. The correlation of the amplitude (phase) quadratures is measured to be 4.0±0.2 (4.0±0.4)dB below the quantum noise limit. The sum criterion for these squeezing variances 0.80±0.03<2 verifies the nonseparability of the state. The product of the inferred uncertainties for one beam (0.64±0.08) is well below the EPR limit of unity
Composite Cluster States and Alternative Architectures for One- Way Quantum Computation
We propose a new architecture for the measurement-based quantum computation
model. The new design relies on small composite light-atom primary clusters.
These are then assembled into cluster arrays using ancillary light modes and
the actual computation is run on such a cellular cluster. We show how to create
the primary clusters, which are Gaussian cluster states composed of both light
and atomic modes. These are entangled via QND interactions and beamsplitters
and the scheme is well described within the continuous-variable covariance
matrix formalism.Comment: arXiv admin note: text overlap with arXiv:1007.040
Quantum properties of the codirectional three-mode Kerr nonlinear coupler
We investigate the quantum properties for the codirectional three-mode Kerr
nonlinear coupler. We investigate single-, two- and three-mode quadrature
squeezing, Wigner function and purity. We prove that this device can provide
richer nonclassical effects than those produced by the conventional coupler,
i.e. the two-mode Kerr coupler. We show that it can provide squeezing and the
quadrature squeezing exhibiting leaf-revival-collapse phenomenon in dependence
on the values of the interaction parameters. In contrast to the conventional
Kerr coupler two different forms of cat states can be simultaneously generated
in the waveguides. We deduce conditions required for the complete
disentanglement between the components of the system.Comment: 23 pages, 6 figure
Influence of modal loss on the quantum state generation via cross-Kerr nonlinearity
In this work we investigate an influence of decoherence effects on quantum
states generated as a result of the cross-Kerr nonlinear interaction between
two modes. For Markovian losses (both photon loss and dephasing), a region of
parameters when losses still do not lead to destruction of non-classicality is
identified. We emphasize the difference in impact of losses in the process of
state generation as opposed to those occurring in propagation channel. We show
moreover, that correlated losses in modern realizations of schemes of large
cross-Kerr nonlinearity might lead to enhancement of non-classicality.Comment: To appear in PR
Gaussian multipartite bound information
We demonstrate the existence of Gaussian multipartite bound information which
is a classical analog of Gaussian multipartite bound entanglement. We construct
a tripartite Gaussian distribution from which no secret key can be distilled,
but which cannot be created by local operations and public communication.
Further, we show that the presence of bound information is conditional on the
presence of a part of the adversary's information creatable only by private
communication. Existence of this part of the adversary's information is found
to be a more generic feature of classical analogs of quantum phenomena obtained
by mapping of non-classically correlated separable quantum states.Comment: 5 pages, 1 figur
Universal Quantum Computation with Continuous-Variable Abelian Anyons
We describe how continuous-variable abelian anyons, created on the surface of
a continuous-variable analogue of Kitaev's lattice model can be utilized for
quantum computation. In particular, we derive protocols for the implementation
of quantum gates using topological operations. We find that the topological
operations alone are insufficient for universal quantum computation which leads
us to study additional non-topological operations such as offline squeezing and
single-mode measurements. It is shown that these in conjunction with a
non-Gaussian element allow for universal quantum computation using
continuous-variable abelian anyons
Highly non-Gaussian states created via cross-Kerr nonlinearity
We propose a feasible scheme for generation of strongly non-Gaussian states
using the cross-Kerr nonlinearity. The resultant states are highly
non-classical states of electromagnetic field and exhibit negativity of their
Wigner function, sub-Poissonian photon statistics, and amplitude squeezing.
Furthermore, the Wigner function has a distinctly pronounced ``banana'' or
``crescent'' shape specific for the Kerr-type interactions, which so far was
not demonstrated experimentally. We show that creating and detecting such
states should be possible with the present technology using electromagnetically
induced transparency in a four-level atomic system in N-configuration.Comment: 12 pages, 7 figure
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