Jaewan Kim

Quantum teleportation and Bell’s inequality using single-particle entanglement

©2000 The American Physical Society URL: http://link.aps.org/abstract/PRA/v63/e012305 DOI: 10.1103/PhysRevA.63.012305 PACS: 03.67.-a, 03.65.Ta, 42.50.-p

CONVEX-ROOF EXTENDED NEGATIVITY AS AN ENTANGLEMENT MEASURE FOR BIPARTITE QUANTUM SYSTEMS

We extend the concept of negativity, a good measure of entanglement for bipartite pure states, to mixed states by means of the convex-roof extension. We show that the measure does not increase under local quantum operations and classical communication, and derive explicit formulas for the entanglement measure of isotropic states and Werner states, applying the formalism presented by Vollbrecht and Werner [Phys. Rev. A 64, 062307 (2001)].

COLLECTIVE REMOTE STATE PREPARATION

We show that any M ≥ 2 distant parties who independently share the complete classical knowledge of a secret qubit state can collectively prepare the state at another remote location. Two distinct schemes for such a task are proposed: one via a single (M + 1)-partite GHZ-type state and the other via M EPR-type pairs. Analytical expressions of the total success probability are derived explicitly for both the schemes. Of interest is the M-dependence of both the success probability and the receivers action. We also construct simple quantum circuits for the two-qubit operators whose execution is necessary to accomplish the schemes.

Entanglement of electron spins of noninteracting electron gases

We study entanglement of electron spins in many-body systems based on the Greens function approach. As an application we obtain the two-particle density matrix of a noninteracting electron gas and identify its two-spin density matrix as a Werner state. We calculate entanglement measures, a classical correlation, mutual information, and a pair-distribution function of two electrons at zero and finite temperatures. We find that changes of entanglement measures are proportional to

Entanglement criteria via the uncertainty relations in su(2) and su(1,1) algebras: Detection of non-Gaussian entangled states

{T}^{2}

Quantum cryptography using single-particle entanglement

at low temperatures.

Entanglement between qubits induced by a common environment with a gap

We derive a class of inequalities, from the uncertainty relations of the su(1,1) and the su(2) algebra in conjunction with partial transposition, that must be satisfied by any separable two-mode states. These inequalities are presented in terms of the su(2) operators

Entanglement swapping secures multiparty quantum communication

{J}_{x}=({a}^{\ifmmode\dagger\else\textdagger\fi{}}b+a{b}^{\ifmmode\dagger\else\textdagger\fi{}})∕2

Shor-Preskill-type security proof for quantum key distribution without public announcement of bases

,

Generation of two-mode nonclassical motional states and a Fredkin gate operation in a two-dimensional ion trap

{J}_{y}=({a}^{\ifmmode\dagger\else\textdagger\fi{}}b\ensuremath{-}a{b}^{\ifmmode\dagger\else\textdagger\fi{}})∕2i