Mathematical Structure of Rabi Oscillations in the Strong Coupling Regime

In this paper we generalize the Jaynes--Cummings Hamiltonian by making use of some operators based on Lie algebras su(1,1) and su(2), and study a mathematical structure of Rabi floppings of these models in the strong coupling regime. We show that Rabi frequencies are given by matrix elements of generalized coherent operators (quant--ph/0202081) under the rotating--wave approximation. In the first half we make a general review of coherent operators and generalized coherent ones based on Lie algebras su(1,1) and su(2). In the latter half we carry out a detailed examination of Frasca (quant--ph/0111134) and generalize his method, and moreover present some related problems. We also apply our results to the construction of controlled unitary gates in Quantum Computation. Lastly we make a brief comment on application to Holonomic Quantum Computation.Comment: Latex file, 24 pages. I added a new section (Quantum Computation), so this paper became self-contained in a certain sens

Scalar Glueball--Quarkonium Mixing and the Structure of the QCD Vacuum

We use Ward identities of broken scale invariance to infer the amount of scalar glueball--$\bar{q}q$ meson mixing from the ratio of quark and gluon condensates in the QCD vacuum. Assuming dominance by a single scalar state, as suggested by a phase-shift analysis, we find a mixing angle $\gamma \sim 36^{\circ}$, corresponding to near-maximal mixing of the glueball and $\bar{s}s$ components.Comment: 7 pages, LaTe

Robust and Scalable Scheme to Generate Large-Scale Entanglement Webs

We propose a robust and scalable scheme to generate an $N$-qubit $W$ state among separated quantum nodes (cavity-QED systems) by using linear optics and postselections. The present scheme inherits the robustness of the Barrett-Kok scheme [Phys. Rev. A {\bf 71}, 060310(R) (2005)]. The scalability is also ensured in the sense that an arbitrarily large $N$-qubit $W$ state can be generated with a quasi-polynomial overhead $\sim 2^{O[(\log_2 N)^2]}$. The process to breed the $W$ states, which we introduce to achieve the scalability, is quite simple and efficient, and can be applied for other physical systems.Comment: 5 pages, 3 figure

Blind quantum computation protocol in which Alice only makes measurements

Blind quantum computation is a new secure quantum computing protocol which enables Alice who does not have sufficient quantum technology to delegate her quantum computation to Bob who has a fully-fledged quantum computer in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous protocols, Alice needs to have a device which generates quantum states, such as single-photon states. Here we propose another type of blind computing protocol where Alice does only measurements, such as the polarization measurements with a threshold detector. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols ease Alice's burden. Furthermore, the security of our protocol is based on the no-signaling principle, which is more fundamental than quantum physics. Finally, our protocols are device independent in the sense that Alice does not need to trust her measurement device in order to guarantee the security.Comment: 9 pages, 3 figure

Attractor Universe in the Scalar-Tensor Theory of Gravitation

In the scalar-tensor theory of gravitation it seems nontrivial to establish if solutions of the cosmological equations in the presence of a cosmological constant behave as attractors independently of the initial values. We develop a general formulation in terms of two-dimensional phase space. We show that there are two kinds of fixed points, one of which is an attractor depending on the coupling constant and equation of state. In the case with a power-law potential in the Jordan frame, we also find new type of inflation caused by the coupling to the matter fluid

Low temperature specific heat of La_{3}Pd_{4}Ge_{4} with U_{3}Ni_{4}Si_{4}-type structure

Low temperature specific heat has been investigated in a novel ternary superconductor La_{3}Pd_{4}Ge_{4} with an U_{3}Ni_{4}Si_{4}-type structure consisting of the alternating BaAl_{4} (ThCr_{2}Si_{2})- and AlB$_{2}$-type layers. A comparative study with the related ThCr_{2}Si_{2}-type superconductor LaPd_{2}Ge_{2}, one of the layers in La_{3}Pd_{4}Ge_{4}, is also presented. From the normal state specific heat, the Sommerfeld coefficient $\gamma_{n} = 27.0$ mJ/mol K^2 and the Debye temperature $\Theta_{\rm D}$ = 256 K are derived for the La_{3}Pd_{4}Ge_{4}, while those for the LaPd_{2}Ge_{2} are $\gamma_{n} =8.26$ mJ/mol K^2 and $\Theta_{\rm D}$ = 291 K. The La_{3}Pd_{4}Ge_{4} has moderately high electronic density of state at the Fermi level. Electronic contribution on the specific heat, $C_{\rm el}$, in each compound is well described by the BCS behavior, suggesting that both of the La_{3}Pd_{4}Ge_{4} and the LaPd_{2}Ge_{2} have fully opened isotropic gap in the superconducting state

China's Current Account and Exchange Rate

We examine whether the Chinese exchange rate is misaligned and how Chinese trade flows respond to the exchange rate and to economic activity. We find, first, that the Chinese currency, the renminbi (RMB), is substantially below the value predicted by estimates based upon a cross-country sample, when using the 2006 vintage of the World Development Indicators. The economic magnitude of the mis-alignment is substantial -- on the order of 50 percent in log terms. However, the misalignment is typically not statistically significant, in the sense of being more than two standard errors away from the conditional mean. Moreover, this finding disappears completely when using the most recent 2008 vintage of data; then the estimated undervaluation is on the order of 10 percent. Second, we find that Chinese multilateral trade flows respond to relative prices -- as represented by a trade weighted exchange rate -- but the relationship is not always precisely estimated. In addition, the direction of the effects is sometimes different from what is expected a priori. For instance, Chinese ordinary imports actually rise in response to a RMB depreciation; however, Chinese exports appear to respond to RMB depreciation in the expected manner, as long as a supply variable is included. In that sense, Chinese trade is not exceptional. Furthermore, Chinese trade with the United States appears to behave in a standard manner -- especially after the expansion in the Chinese manufacturing capital stock is accounted for. Thus, the China-US trade balance should respond to real exchange rate and relative income movements in the anticipated manner. However, in neither the case of multilateral nor bilateral trade flows should one expect quantitatively large effects arising from exchange rate changes. And, of course, these results are not informative with regard to the question of how a change in the RMB/USD exchange rate would affect the overall US trade deficit.

China, Hong Kong, and Taiwan: A Quantitative Assessment of Real and Financial Integration

The status of real and financial integration of China, Hong Kong, and Taiwan is investigated using monthly data on one-month interbank rates, exchange rates, and prices. Specifically, the degree of integration is assessed based on the empirical validity of real interest parity, uncovered interest parity, and relative purchasing power parity. There is evidence these parity conditions tend to hold over longer periods, although they do not hold instantaneously. Overall, the magnitude of deviations from the parity conditions is shrinking over time. In particular, China and Hong Kong appear to have experienced significant increases in integration during the sample period. It is also found that exchange rate variability plays a major role in determining the variability of deviations from these parity conditions.uncovered interest parity, real interest parity, purchasing power parity, exchange rates, capital mobility, market integration

Formal Relation among Various Hermitian and non-Hermitian Effective Interactions

A general definition of the model-space effective interaction is given. The energy-independent effective hamiltonians derived in a time-independent way are classified systematically.Comment: To appear in IJMPE; Proceedings of "Blueprints for the Nucleus," Istanbul, Turkey, May 200