Showing papers by "Myungshik Kim published in 2004"
TL;DR: In this article, a linear superposition of two macroscopically distinguishable optical coherent states can be generated using a single photon source and simple all-optical operations, which does not need photon number resolving measurements nor Kerr-type nonlinear interactions.
Abstract: It is shown that a linear superposition of two macroscopically distinguishable optical coherent states can be generated using a single photon source and simple all-optical operations. Weak squeezing on a single photon, beam mixing with an auxiliary coherent state, and photon detecting with imperfect threshold detectors are enough to generate a coherent state superposition in a free propagating optical field with a large coherent amplitude (alpha>2) and high fidelity (F>0.99). In contrast to all previous schemes to generate such a state, our scheme does not need photon number resolving measurements nor Kerr-type nonlinear interactions. Furthermore, it is robust to detection inefficiency and exhibits some resilience to photon production inefficiency.
168 citations
TL;DR: In this paper, a beam splitter, homodyne measurement, and a very small Kerr nonlinear effect are used to generate a macroscopic superposition state of a free-propagating optical field.
Abstract: We suggest a scheme to generate a macroscopic superposition state (Schrodinger cat state) of a free-propagating optical field using a beam splitter, homodyne measurement, and a very small Kerr nonlinear effect. Our scheme makes it possible to reduce considerably the required nonlinear effect to generate an optical cat state using simple and efficient optical elements.
72 citations
TL;DR: In this paper, the authors proposed a theoretical scheme for the simulation of quantum random walks on a line using beam splitters, phase shifters, and photodetectors, which enables them to simulate a quantum random walk using of the wave nature of classical light fields.
Abstract: We suggest a theoretical scheme for the simulation of quantum random walks on a line using beam splitters, phase shifters, and photodetectors. Our model enables us to simulate a quantum random walk using of the wave nature of classical light fields. Furthermore, the proposed setup allows the analysis of the effects of decoherence. The transition from a pure mean-photon-number distribution to a classical one is studied varying the decoherence parameters.
70 citations
TL;DR: In this article, a scheme to physically interface superconducting nanocircuits and quantum optics is proposed, which is able to drive an initially separable state of the qubits into an almost pure, highly entangled state suitable for quantum information processing.
Abstract: We propose a scheme to physically interface superconducting nanocircuits and quantum optics. We address the transfer of quantum information between systems having different physical natures and defined in Hilbert spaces of different dimensions. In particular, we investigate the transfer of the entanglement initially in a nonclassical state of an infinite dimensional system to a pair of superconducting charge qubits. This setup is able to drive an initially separable state of the qubits into an almost pure, highly entangled state suitable for quantum information processing.
66 citations
TL;DR: In this article, a general correlation observable of two parties was proposed for the purpose of a non-locality test by utilizing local d-outcome measurements with SU(d) transformations and classical communications.
Abstract: For the purpose of a nonlocality test, we propose a general correlation observable of two parties by utilizing local d-outcome measurements with SU(d) transformations and classical communications. Generic symmetries of the SU(d) transformations and correlation observables are found for the test of nonlocality. It is shown that these symmetries dramatically reduce the number of numerical variables, which is important for numerical analysis of nonlocality. A linear combination of the correlation observables, which is reduced to the Clauser–Horne–Shimony-Holt (CHSH) Bell's inequality for two outcome measurements, leads to the Collins–Gisin–Linden–Massar–Popescu (CGLMP) nonlocality test for d-outcome measurement. As a system to be tested for its nonlocality, we investigate a continuous-variable (CV) entangled state with d measurement outcomes. It allows the comparison of nonlocality based on different numbers of measurement outcomes on one physical system. In our example of the CV state, we find that a pure entangled state of any degree violates Bell's inequality for d(≥2) measurement outcomes when the observables are of SU(d) transformations.
24 citations
TL;DR: In this paper, the authors investigate the disentangling of mecha-nism by considering the quantum correlation between a two-mode squeezed state and a thermal environment, and they show that a pure state decoheres into a mixed state as the system entangles with an environment which is initially in a pure states.
Abstract: School of Mathematics and Physics, The Queen’s University, Belfast BT7 1NN, United Kingdom(Received 14 November 2003)A pure state decoheres into a mixed state as the system entangles with an environment whichis initially in a pure state. However, it is not de nite that the system becomes entangled with acon ned environment with which it only ever interacts. We investigate the disentangling mecha-nism by considering the quantum correlation between a two-mode squeezed state and a thermalenvironment.
2 citations
TL;DR: In this paper, the authors proposed an experimentally realizable scheme to test entanglement of a mixed Gaussian continuous-variable state, which is then shown to be directly related to joint homodyne measurements.
Abstract: We suggest an experimentally realizable scheme to test entanglement of a mixed Gaussian continuous-variable state We find that the entanglement condition is simplified for the family of Gaussian states which are relevant to experimental realization The entanglement condition is then shown to be directly related to joint homodyne measurements We show how robust the proposed test of entanglement is against imperfect detection efficiency