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Inseparability inequalities for higher-order moments for bipartite systems
There are several examples of bipartite entangled states of continuous
variables for which the existing criteria for entanglement using the
inequalities involving the second order moments are insufficient. We derive new
inequalities involving higher order correlation, for testing entanglement in
non-Gaussian states. In this context we study an example of a non-Gaussian
state, which is a bipartite entangled state of the form .
Our results open up an avenue to search for new inequalities to test
entanglement in non-Gaussian states.Comment: 7 pages, Submitte
Measuring arbitrary-order coherences: Tomography of single-mode multiphoton polarization-entangled states
A scheme is discussed for measuring Nth-order coherences of two orthogonally
polarized light fields in a single spatial mode at very limited experimental
cost. To implement the scheme, the only measurements needed are the Nth-order
intensity moments after the light beam has passed through two quarter-wave
plates, one half-wave plate, and a polarizing beam splitter for specific
settings of the wave plates. It is shown that this method can be applied for
arbitrarily large N. A set of explicit values is given for the settings of the
wave plates, constituting an optimal measurement of the Nth-order coherences
for any N. For Fock states the method introduced here corresponds to a full
state tomography. Applications of the scheme to systems other than polarization
optics are discussed.Comment: 6 pages, 1 figure, 1 table, published versio
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