Creating multiphoton-polarization bound entangled states

Abstract

Bound entangled states are the exotic objects in the entangled world. They require entanglement to create them, but once they are formed, it is not possible to locally distill any free entanglement from them. It is only until recently that a few bound entangled states were realized in the laboratory. Motivated by these experiments, we propose schemes for creating various classes of bound entangled states with photon polarization. These include Acín-Bruß-Lewenstein-Sanpara states, Dür's states, Lee-Lee-Kim bound entangled states, and an unextendibleproduct-basis bound entangled state.

On four-photon entanglement from parametric down-conversion process

“…As a quantum resource, multiphoton entanglement [1,2] plays an important role in both theoretical studies and experimental techniques. One of the attractive aspects of this field is how to generate the desired multiphoton entangled states [3][4][5][6][7][8][9][10][11][12][13]. Since a spontaneous parametric down-conversion (PDC) [14][15][16][17] source is capable of creating pairs of entangled photons, in general, a standard method of generating the multiphoton entanglement is to evolve the pairs emitted from respective source with a set of passive optical elements [2].…”

Distillation of free entanglement from bound entangled states using weak measurements

“…It was also indicated [13,14] that application of any bound-entangled state along with some free-entangled state can increase the teleportation power of the free-entangled state. Preparation of some particular bipartite and multipartite bound-entangled states is now possible in nuclear magnetic resonance [15], optical [16][17][18][19][20], as well as ion-trapped systems [21]. Moreover, bound entanglement can naturally arise, e.g., in the XY spin model through applying an external magnetic field [22], in the Jaynes-Cummings model [23], as well in strongly-correlated graph states at thermal equilibrium [24,25].…”

Exploration of multiphoton entangled states by using weak nonlinearities

“…Generally, a spontaneous parametric down-conversion (PDC) source 29 30 is capable of emitting pairs of strongly time-correlated photons in two spatial modes. As extensions of interest, with linear optics and nonlinear optical materials several schemes for creating multiphoton entangled states have been proposed 31 32 33 34 35 36 37 . For a large number of photons, however, there are some technological challenges such as probabilistic emission of PDC sources and imperfect detectors.…”