Eylee Jung

Greenberger-Horne-Zeilinger versus W states : Quantum teleportation through noisy channels

Eylee Jung, Mi-Ra Hwang, You Hwan Ju, Min-Soo Kim, Sahng-Kyoon Yoo, Hungsoo Kim, D. K. Park, Jin-Woo Son, S. Tamaryan, Seong-Keuck Cha 1 Department of Physics, Kyungnam University, Masan, 631-701, Korea 2 Department of Mathematics, Kyungnam University, Masan, 631-701, Korea 3 Green University, Hamyang, 676-872, Korea 4 The Institute of Basic Science, Kyungnam University, Masan, 631-701, Korea 5 Theory Department, Yerevan Physics Institute, Yerevan-36, 375036, Armenia 6 Department of Chemistry, Kyungnam University, Masan, 631-701, Korea Abstract Which state does lose less quantum information between GHZ and W states when they are prepared for two-party quantum teleportation through noisy channel? We address this issue by solving analytically a master equation in the Lindbald form with introducing the noisy channels which makes the quantum channels to be mixed states. It is found that the answer of the question is dependent on the type of the noisy channel. If, for example, the noisy channel is (L2,x, L3,x, L4,x)-type where L s denote the Lindbald operators, GHZ state is always more robust than W state, i.e. GHZ state preserves more quantum information. In, however, (L2,y, L3,y, L4,y)-type channel the situation becomes completely reversed. In (L2,z, L3,z, L4,z)-type channel W state is more robust than GHZ state when the noisy parameter (κ) is comparatively small while GHZ state becomes more robust when κ is large. In isotropic noisy channel we found that both states preserve equal amount of quantum information. A relation between the average fidelity and entanglement for the mixed state quantum channels are discussed.

Absorption and emission spectra of an higher-dimensional Reissner–Nordström black hole

Abstract The absorption and emission problems of the brane-localized and bulk scalars are examined when the spacetime is a ( 4 + n ) -dimensional Reissner–Nordstrom black hole. Making use of an appropriate analytic continuation, we compute the absorption and emission spectra in the full range of particles energy. For the case of the brane-localized scalar the presence of the nonzero inner horizon parameter r − generally enhances the absorptivity and suppresses the emission rate compared to the case of the Schwarzschild phase. The low-energy absorption cross section exactly equals to 4 π r + 2 , two-dimensional horizon area. The effect of the extra dimensions generally suppresses the absorptivity and enhances the emission rate, which results in the disappearance of the oscillatory pattern in the total absorption cross section when n is large. For the case of the bulk scalar the effect of r − on the spectra is similar to that in the case of the brane-localized scalar. The low-energy absorption cross section equals to the area of the horizon hypersurface. In the presence of the extra dimensions the total absorption cross section tends to be inclined with a positive slope. It turns out that the ratio of the missing energy over the visible one decreases with increase of r − .

Bulk versus Brane in the Absorption and Emission : 5D Rotating Black Hole Case

Abstract The absorption and emission spectra for the minimally-coupled brane and bulk scalar fields are numerically computed when the spacetime is a 5d rotating black hole carrying the two different angular momentum parameters a and b . The effect of the superradiant scattering in the spectra is carefully examined. It is shown that the low-energy limit of the total absorption cross section always equal to the area of the non-spherically symmetric horizon, i.e., 4 π ( r H 2 + a 2 ) for the brane scalar and 2 π 2 ( r H 2 + a 2 ) ( r H 2 + b 2 ) / r H for the bulk scalar where r H is an horizon radius. The energy amplification for the bulk scalar is roughly order of 10 −9 % while that for the brane scalar is order of unity. This indicates that the effect of the superradiance is negligible for the case of the bulk scalar. Thus the standard claim that black holes radiate mainly on the brane is not changed although the effect of the superradiance is taken into account. The physical implication of this fact is discussed in the context of TeV-scale gravity.

Low-energy absorption cross section for massive scalar and Dirac fermion by (4+n)-dimensional Schwarzschild black hole

Motivated by the brane-world scenarios, we study the absorption problem when the spacetime background is (4+n)-dimensional Schwarzschild black hole. We compute the low-energy absorption cross sections for the brane-localized massive scalar, brane-localized massive Dirac fermion, and massive bulk scalar. For the case of brane-localized massive Dirac fermion we introduce the particles spin in the traditional Dirac form without invoking the Newman-Penrose method. Our direct introduction of spin enables us to compute contributions to the jth-level partial absorption cross section from orbital angular momenta l = j±1/2. It is shown that the contribution from the low l-level is larger than that from the high l-level in the massive case. In the massless case these two contributions are exactly same with each other. The ratio of low-energy absorption cross sections for Dirac fermion and for scalar is dependent on the number of extra dimensions as 2−(n+3)/(n+1). Thus the ratio factor 1/8 is recovered when n = 0, which Unruh found. The physical importance of this ratio factor is discussed in the context of the brane-world scenario. For the case of bulk scalar our low-energy absorption cross section for S-wave is exactly same with area of the horizon hypersurface in the massless limt, which is an higher-dimensional generaliztion of universality. Our results for all cases turn out to have correct massless and 4d limits.

Three-tangle for rank-three mixed states: Mixture of Greenberger-Horne-Zeilinger, W , and flipped- W states

Three-tangle for a rank-3 mixture composed of Greenberger-Horne-Zeilinger,

Mixed-state entanglement and quantum teleportation through noisy channels

W

Reduced state uniquely defines the Groverian measure of the original pure state

, and flipped-

Does three-tangle properly quantify the three-party entanglement for Greenberger-Horne-Zeilinger-type states?

W

Newton law on the generalized singular brane with and without 4d induced gravity

states is analytically calculated. The optimal decompositions in the full range of parameter space are constructed by making use of the convex-roof extension. We also provide an analytical technique, which determines whether or not an arbitrary rank-3 state has vanishing three-tangle. This technique is developed by making use of the Bloch sphere

Bulk versus brane emissivities of photon fields: For the case of higher-dimensional Schwarzschild phase

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