arXiv subjects

Eylee Jung

Publications and source records attributed to Eylee Jung.

53 records · Page 3Linked to original sources

arXiv2008

Reduced State Uniquely Defines Groverian Measure of Original Pure State

Groverian and Geometric entanglement measures of the n-party pure state are expressed by the (n-1)-party reduced state density operator directly. This main theorem derives several important consequences. First, if two pure n-qudit states have reduced states of (n-1)-qudits, which are equivalent under local unitary(LU) transformations, then they have equal Groverian and Geometric entanglement measures. Second, both measures have an upper bound for pure states. However, this upper bound is reached only for two qubit systems. Third, it converts effectively the nonlinear eigenvalue problem for three qubit Groverian measure into linear eigenvalue equations. Some typical solutions of these linear equations are written explicitly and the features of the general solution are discussed in detail.

quant-ph↗

arXiv2008

Perfect Quantum Teleportation and Superdense coding with $P_{max} = 1/2$ states

We conjecture that criterion for perfect quantum teleportation is that the Groverian entanglement of the entanglement resource is $1/\sqrt{2}$. In order to examine the validity of our conjecture we analyze the quantum teleportation and superdense coding with $|Φ> = (1/\sqrt{2}) (|00q_1> + |11q_2>)$, where $|q_1>$ and $|q_2>$ are arbitrary normalized single qubit states. It is shown explicitly that $|Φ>$ allows perfect two-party quantum teleportation and superdense coding scenario. Next we compute the Groverian measures for $|ψ>=\sqrt{1/2 - b^2}|100>+b |010>+a|001> +\sqrt{1/2-a^2}|111>$ and $|\tildeψ>=a|000>+b|010>+\sqrt{1/2 - (a^2+b^2)}|100> + (1/\sqrt{2}) |111>$, which also allow the perfect quantum teleportation. It is shown that both states have $1/\sqrt{2}$ Groverian entanglement measure, which strongly supports that our conjecture is valid.

quant-ph↗

arXiv2008

Mixed-State Entanglement and Quantum Teleportation through Noisy Channels

The quantum teleportation with noisy EPR state is discussed. Using an optimal decomposition technique, we compute the concurrence, entanglement of formation and Groverian measure for various noisy EPR resources. It is shown analytically that all entanglement measures reduce to zero when $\bar{F} \leq 2/3$, where $\bar{F}$ is an average fidelity between Alice and Bob. This fact indicates that the entanglement is a genuine physical resource for the teleportation process. This fact gives valuable clues on the optimal decomposition for higher-qubit mixed states. As an example, the optimal decompositions for the three-qubit mixed states are discussed by adopting a teleportation with W-state

quant-ph↗

arXiv2007

Amplitude Damping for single-qubit System with single-qubit mixed-state Environment

We study a generalized amplitude damping channel when environment is initially in the single-qubit mixed state. Representing the affine transformation of the generalized amplitude damping by a three-dimensional volume, we plot explicitly the volume occupied by the channels simulatable by a single-qubit mixed-state environment. As expected, this volume is embedded in the total volume by the channels which is simulated by two-qubit enviroment. The volume ratio is approximately 0.08 which is much smaller than 3/8, the volume ratio for generalized depolarizing channels.

quant-ph↗

arXiv2007

Validity of Emparan-Horowitz-Myers argument in Hawking radiation into massless spin-2 fields

The Hawking radiation for massless spin-2 fields is numerically studied when the spacetime background is (4+n)-dimensional Schwarzschild black hole phase. In order to check the validity of the Emparan-Horowitz-Myers argument, {\it black holes radiate mainly on the brane}, we assume that the radial equation for the massless spin-2 fields propagating on the brane obeys the master equation approximately. The transmission coefficient is computed explicitly by making use of the Hawking-Hartle theorem. It is shown that the total emission rates into the bulk are dominant compared to the rates on the visible brane when $n \geq 3$. However, the bulk-to-brane relative emissivities per degree of freedom always remain O(1) roughly. The experimental significance of these results in the production of mini black holes in future colliders is briefly discussed.

hep-th↗

arXiv2007

Quantum Teleportation and Von Neumann Entropy

The single qubit quantum teleportation (sender and receiver are Alice and Bob respectively) is analyzed from the aspect of the quantum information theories. The various quantum entropies are computed at each stage, which ensures the emergence of the entangled states in the intermediate step. The mutual information $S(B:C)$ becomes non-zero before performing quantum measurement, which seems to be consistent to the original purpose of the quantum teleportation. It is shown that if the teleported state $|ψ>$ is near the computational basis, the quantum measurement in $C$-system is dominantly responsible for the joint entropy $S(A,C)$ at the final stage. If, however, $|ψ>$ is far from the computational basis, this dominant responsibility is moved into the quantum measurement of system $A$. A possible extension of our results are briefly discussed.

quant-ph↗

arXiv2007

Bulk versus Brane Emissivities of Photon Fields: For the case of Higher-Dimensional Schwarzschild Phase

The emission spectra for the spin-1 photon fields are computed when the spacetime is a $(4+n)$-dimensional Schwarzschild phase. For the case of the bulk emission we compute the spectra for the vector mode and scalar mode separately. Although the emissivities for the scalar mode is larger than those for the vector mode when $n$ is small, the emissivities for the vector mode photon become dominant rapidly with increasing $n$. For the case of the brane emission the emission spectra are numerically computed by making use of the complex potential method. Comparision of the total bulk emissivities with total brane emissivities indicates that the effect of the field spin makes the bulk emission to be rapidly dominant with increasing $n$. However, the bulk-to-brane relative emissivity per degree of freedom always remains smaller than unity. The importance for the spin-2 graviton emission problem is discussed.

hep-th↗

arXiv2005

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

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, {\it i.e.} $4π(r_H^2 + a^2)$ for the brane scalar and $2π^2 (r_H^2 + a^2) (r_H^2 + b^2)/r_H$ 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 {\it 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 fac t is discussed in the context of TeV-scale gravity.

hep-th↗

arXiv2005

Condition for Superradiance in Higher-dimensional Rotating Black Holes

It is shown that the superradiance modes always exist in the radiation by the $(4+n)$-dimensional rotating black holes. Using a Bekenstein argument the condition for the superradiance modes is shown to be $0 < ω< m Ω$ for the scalar, electromagnetic and gravitational waves when the spacetime background has a single angular momentum parameter about an axis on the brane, where $Ω$ is a rotational frequency of the black hole and $m$ is an azimuthal quantum number of the radiated wave.

hep-th↗

arXiv2005

Condition for the Superradiance Modes in Higher-Dimensional Rotating Black Holes with Multiple Angular Momentum Parameters

The condition for the existence of the superradiance modes is derived for the incident scalar, electromagnetic and gravitational waves when the spacetime background is a higher-dimensional rotating black hole with multiple angular momentum parameters. The final expression of the condition is $0 < ω< \sum_i m_i Ω_i$, where $Ω_i$ is an angular frequency of the black hole and, $ω$ and $m_i$ are the energy of the incident wave and the $i$-th azimuthal quantum number. The physical implication of this condition in the context of the brane-world scenarios is discussed.

hep-th↗

arXiv2005

Ratio of absorption cross section for Dirac fermion to that for scalar in the higher-dimensional black hole background

The ratio of the low-energy absorption cross section for Dirac fermion to that for minimally coupled scalar is computed when the spacetimes are various types of the higher-dimensional Reissner-Nordström black holes. It is found that the low-energy absorption cross sections for the Dirac fermion always goes to zero in the extremal limit regardless of the detailed geometry of the spacetime. The physical importance of our results is discussed in the context of the brane-world scenarios and string theories.

hep-th↗

arXiv2005

Absorption and Emission Spectra of an higher-dimensional Reissner-Nordström black hole

The absorption and emission problems of the brane-localized and bulk scalars are examined when the spacetime is a $(4+n)$-dimensional Reissner-Nordström black hole. Making use of an appropriate analytic continuation, we compute the absorption and emission spectra in the full range of particle's 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 $4πr_+^2$, 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 {\it missing} energy over the {\it visible} one decreases with increase of $r_-$.

hep-th↗

arXiv2004

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 particle's spin in the traditional Dirac form without invoking the Newman-Penrose method. Our direct introduction of spin enables us to compute contributions to the $j$th-level partial absorption cross section from orbital angular momenta $\ell = j \pm 1/2$. It is shown that the contribution from the low $\ell$-level is larger than that from the high $\ell$-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.

hep-th↗

arXiv2004

Proof of universality for the absorption of massive scalars by the higher-dimensional Reissner-Nordström black holes

Motivated by black hole experiments as a consequence of the TeV-scale gravity arising from modern brane-world scenarios, we study the absorption problem for the massive scalars when the spacetime background is a $(4+n)$-dimensional Reissner-Nordström black hole. For analytic computation we adopt the near-extreme condition in the spacetime background. It is shown that the low-energy absorption cross section for the s-wave case holds an universality, {\it i.e.} the absorption cross section equals to the area of the black hole horizon divided by a velocity parameter.

hep-th↗

arXiv2004

Effect of Scalar Mass in the Absorption and Emission Spectra of Schwarzschild Black Hole

Following Sanchez's approach we investigate the effect of scalar mass in the absorption and emission problems of 4d Schwarzschild black hole. The absorption cross sections for arbitrary angular momentum of the scalar field are computed numerically in the full range of energy by making use of the analytic near-horizon and asymptotic solutions and their analytic continuations. The scalar mass makes an interesting effect in the low-energy absorption cross section for S-wave. Unlike the massless case, the cross section decreases with increasing energy in the extremely low-energy regime. As a result the universality, {\it i.e.} low-energy cross section for S-wave is equal to the horizon area, is broken in the presence of mass. If the scalar mass is larger than a critical mass, the absorption cross section becomes monotonically decreasing function in the entire range of energy. The Hawking emission is also calculated numerically. It turns out that the Planck factor generally suppresses the contribution of higher partial waves except S-wave. The scalar mass in general tends to reduce the emission rate.

hep-th↗

arXiv2004

Absorption Cross Section for S-wave massive Scalar

We examine the absorption cross section of the massive scalar field for the higher-dimensional extended object. Adopting the usual quantum mechanical matching conditions between the asymptotic and near-horizon solutions in radial equation, we check whether or not the universal property of the absorption cross section, which is that the low-energy cross section is proportional to the surface area of horizon, is maintained when the mass effect is involved. It is found that the mass effect in general does not break the universal property of the cross section if particular conditions are required to the spacetime geometry. However, the mass-dependence of the cross section is very sensitive to the spacetime property in the near-horizon regime.

hep-th↗

arXiv2003

Newton Law on the Generalized Singular Brane with and without 4d Induced Gravity

Newton law arising due to the gravity localized on the general singular brane embedded in $AdS_5$ bulk is examined in the absence or presence of the 4d induced Einstein term. For the RS brane, apart from the subleading correction, Newton potential obeys 4d-type and $5d$-type gravitational law at long- and short-ranges if it were not for the induced Einstein term. The 4d induced Einstein term generates an intermediate range at short distance, in which the $5d$ Newton potential $1/r^2$ emerges. For Neumann brane the long-range behavior of Newton potential is exponentially suppressed regardless of the existence of the induced Einstein term. For Dirichlet brane the expression of Newton potential is dependent on the renormalized coupling constant $v^{ren}$. At particular value of $v^{ren}$ Newton potential on Dirichlet brane exhibits a similar behavior to that on RS brane. For other values the long-range behavior of Newton potential is exponentially suppressed as that in Neumann brane.

hep-th↗