Impossibility of large phase shifts via the "giant Kerr effect" with single-photon wavepackets

An approximate analytical solution is presented, along with numerical calculations, for a system of two single-photon wavepackets interacting via an ideal, localized Kerr medium. It is shown that, because of spontaneous emission into the initially unoccupied temporal modes, the cross-phase modulation in the Schrodinger picture is very small as long as the spectral width of the single-photon pulses is well within the medium's bandwidth. In this limit, the Hamiltonian used can be derived from the "giant Kerr effect" for a four-level atom, under conditions of electromagnetically-induced transparency; it is shown explicitly that the linear absorption in this system increases as the pulse's spectral width approaches the medium's transparency bandwidth, and hence, as long as the absorption probability remains small, the maximum cross-phase modulation is limited to essentially useless values. These results are in agreement with the general, causality- and unitarity-based arguments of Shapiro and co-workers.Comment: 8 pages, 2 figures, to be submitted to Physical Review

Reply to "Comment on "Some implications of the quantum nature of laser fields for quantum computations''''

In this revised reply to quant-ph/0211165, I address the question of the validity of my results in greater detail, by comparing my predictions to those of the Silberfarb-Deutsch model, and I deal at greater length with the beam area paradox. As before, I conclude that my previous results are an (order-of-magnitude) accurate estimate of the error probability introduced in quantum logical operations by the quantum nature of the laser field. While this error will typically (for a paraxial beam) be smaller than the total error due to spontaneous emission, a unified treatment of both effects reveals that they lead to formally similar constraints on the minimum number of photons per pulse required to perform an operation with a given accuracy; these constraints agree with those I have derived elsewhere.Comment: A reply to quant-ph/0211165. Added more calculations and discussion, removed some flippanc

Integritas Personal dan Kepemimpinan Etis

Integrity is very important for a leader. When a leader does not have integrity, then, sooner or later it will destroy the group or organization s/he leads. This occurs because the policies, decisions, attitudes, and actions made by the leader will have wide impact to the organization. A leader will be the center of attention of the members, and whatever they see in her/him will have a huge impact on the organization as a whole. Integrity has been given a lot of meaning; and everything is interconnected, which essentially refers to one\u27s personal qualities, which make a person trustworthy and reliable. In the world of work, integrity appears in the form of good work performance or results. To be able to produce a good performance it is necessary to have competence. With integrity possessed the competence can be directed to produce a good performance. The problem that occurs is a lack of understanding of the relationship between integrity and performance. Generally, they are both understood separately, as stand-alone. But in reality the integrity is manifested through good performance. This applies also to a leader, which results a good performance in implementing ethical leadership. The purpose of this paper is to outline the relationship between integrity and performance, in which competence plays an important role. Integrity is the foundation for leadership, which makes it able to run and produce ethical leadership performance

Gate fidelity of arbitrary single-qubit gates constrained by conservation laws

Recent investigations show that conservation laws limit the accuracy of gate operations in quantum computing. The inevitable error under the angular momentum conservation law has been evaluated so far for the CNOT, Hadamard, and NOT gates for spin 1/2 qubits, while the SWAP gate has no constraint. Here, we extend the above results to general single-qubit gates. We obtain an upper bound of the gate fidelity of arbitrary single-qubit gates implemented under arbitrary conservation laws, determined by the geometry of the conservation law and the gate operation on the Bloch sphere as well as the size of the ancilla.Comment: Title changed; to appear in J. Phys. A: Math. Theor.; 19 pages, 2 figure

Mean-field treatment of the damping of the oscillations of a 1D Bose gas in an optical lattice

We present a theoretical treatment of the surprisingly large damping observed recently in one-dimensional Bose-Einstein atomic condensates in optical lattices. We show that time-dependent Hartree-Fock-Bogoliubov (HFB) calculations can describe qualitatively the main features of the damping observed over a range of lattice depths. We also derive a formula of the fluctuation-dissipation type for the damping, based on a picture in which the coherent motion of the condensate atoms is disrupted as they try to flow through the random local potential created by the irregular motion of noncondensate atoms. We expect this irregular motion to result from the well-known dynamical instability exhibited by the mean-field theory for these systems. When parameters for the characteristic strength and correlation times of the fluctuations, obtained from the HFB calculations, are substituted in the damping formula, we find very good agreement with the experimentally-observed damping, as long as the lattice is shallow enough for the fraction of atoms in the Mott insulator phase to be negligible. We also include, for completeness, the results of other calculations based on the Gutzwiller ansatz, which appear to work better for the deeper lattices.Comment: Extended and revised version, August 200

Quantum limits in interferometric measurements

Quantum noise limits the sensitivity of interferometric measurements. It is generally admitted that it leads to an ultimate sensitivity, the ``standard quantum limit''. Using a semi-classical analysis of quantum noise, we show that a judicious use of squeezed states allows one in principle to push the sensitivity beyond this limit. This general method could be applied to large scale interferometers designed for gravitational wave detection.Comment: 4 page

Toward Peace-Loving Attitude Trough Education Character

Efforts to solve violence had been faced by multi treatments. Violence in education is action over the standar of ethic and rule in education, either physically or disturbing the rights of ones. The actors can be anyone,  including the chief of school, teacher, staff , student, parents and even society. Violence in education is assumed as effect of certain condition. Externally or internally, and it might happen with any trigger. This paper aims to analyse the importance of character building through peace-loving attitude to revitalize the actors of education as evaluation of structure and culture in the educational world. Our educational world recently sometimes shows its arrogancy and even militaristic behavior. While the basic tenet of education is to appreciate the understanding of human behavior in order to be enlighted and free

Steady State Entanglement in Cavity QED

We investigate steady state entanglement in an open quantum system, specifically a single atom in a driven optical cavity with cavity loss and spontaneous emission. The system reaches a steady pure state when driven very weakly. Under these conditions, there is an optimal value for atom-field coupling to maximize entanglement, as larger coupling favors a loss port due to the cavity enhanced spontaneous emission. We address ways to implement measurements of entanglement witnesses and find that normalized cross-correlation functions are indicators of the entanglement in the system. The magnitude of the equal time intensity-field cross correlation between the transmitted field of the cavity and the fluorescence intensity is proportional to the concurrence for weak driving fields.Comment: enhanced discussion, corrected formulas, title change, 1 added figur

Limnological Characterization of the Tristate Oxbow Wetland (Ohio, Indiana)

Author Institution: Department of Botany, Miami UniversityWe conducted a limnological study in bodies of water (Oxbow Lake, North Pond, Great Miami River, Ohio River) comprising the Tristate Oxbow Wetland region of southwestern Ohio and southeastern Indiana. This wetland, an extensive and important wildlife habitat located at the confluence of the Great Miami River and the Ohio River, is a region that has been and may in the future be impacted by industrial and commercial development. The present data suggest that Oxbow Lake and North Pond are strongly influenced by seasonal flooding patterns and resultant nutrient loading from the Great Miami River and the Ohio River. On the basis of physico-chemical and biological parameters, Oxbow Lake can be classified as a eutrophic to hypereutrophic system, while North Pond is mesotrophic to eutrophic