Improving the Fidelity of Optical Zeno Gates via Distillation

We have modelled the Zeno effect Control-Sign gate of Franson et al (PRA 70, 062302, 2004) and shown that high two-photon to one-photon absorption ratios, $\kappa$, are needed for high fidelity free standing operation. Hence we instead employ this gate for cluster state fusion, where the requirement for $\kappa$ is less restrictive. With the help of partially offline one-photon and two-photon distillations, we can achieve a fusion gate with unity fidelity but non-unit probability of success. We conclude that for $\kappa > 2200$, the Zeno fusion gate will out perform the equivalent linear optics gate.Comment: 6 pages, 11 figures, Submitted to PR

European financial integration and corporate governance

The paper studies the link between the integration of European financial markets and corporate governance in Europe. The focus of the paper is on how integration affects the interplay of ownership structures, capital structures, and monitoring, all of which can be used to govern agency problems at the firm level. Integration is a process which comprises the abolition of capital controls, the harmonization of institutions, and the creation of a common currency area. These elements, in turn, affect the liquidity of markets, the cost of monitoring, and the cost of debt. Based on these considerations, implications for changes in the structure of corporate governance systems are derived. --corporate governance,complementarity,financial integration

The end of the Czech miracle? Currency crisis reveals need for institutional reforms

After years of high growth, low unemployment and low inflation, the Czech economy has suffered a sudden setback. Speculative attacks on the currency have forced the Central Bank to abandon its fixed exchange rate. The government has now announced austerity measures to reduce the massive current account deficit. In the short run, these measures will lead to lower growth and higher unemployment. Moreover, the devaluation of the Czech Koruna will make it more difficult to further reduce inflation. The crisis is due in part to the previous boom in domestic absorption. The expansion of absorption has been fuelled by massive capital inflows which helped to maintain the fixed exchange rate. At the same time, productivity growth has been sluggish despite high investment-to-GDP ratios, and wages have increased substantially despite sluggish productivity growth. These developments have contributed to the overvaluation of the exchange rate. As a result, the competitiveness of the tradables sector has been weakened, and the current account deficit has widened dramatically. The policy measures now announced aim at reducing domestic demand by cutting fiscal expenditure, raising taxes, devaluing the currency, and containing wage growth in the public sector. However, the government has so far failed to address the microeconomic issues that are at the heart of these supply-side problems. These include inefficiencies in financial intermediation, ineffective bankruptcy procedures, and weaknesses in the corporate governance of enterprises resulting from mass privatization. Solutions to the problems in the banking and financial sector should comprise tax incentives for banks to provision for loan losses, decentralized debt restructuring, the streamlining of bankruptcy proceedings, upgrading of the court system's resources, and a greater political will to enforce the existing bankruptcy legislation. Opening up for foreign banks more decisively and in particular allowing foreign banks to participate in the privatization of the large commercial banks can help to improve the efficiency of the banking system and the corporate governance role of banks. In order to encourage funds to manage their portfolios for the benefit of investors, funds should be encouraged to register as open-end unit trusts rather than as joint stock companies. On the macroeconomic level, the government is moving in the right direction. As regards the medium term outlook, fundamentals of the Czech economy remain strong. However, decisive and timely action to improve the institutional framework is needed if the economy is to overcome the present crisis and to reach a new, sustainable growth path. --

Financing the transition: Risks and benefits of integrating into the international capital market

This paper surveys the theoretical and empirical evidence on capital account convertibility and assesses its relevance for the reform states of Central and Eastern Europe. Its major findings are that domestic investment conditions matter and that domestic policies can reduce the risk of an abrupt reversal of capital flows. Policymakers must stand ready to adjust the exchange rate but also their fiscal and monetary policies once signs of overheating appear. The effectiveness of controls on capital flows is highly questionable. Moreover, capital controls raise the irreversibility of investment projects and may cause the postponement of investment decisions. The countries under review have made substantial progress towards capital account convertibility and should continue on this track as they strive for membership in the EU.

Adaptive Phase Measurements in Linear Optical Quantum Computation

Photon counting induces an effective nonlinear optical phase shift on certain states derived by linear optics from single photons. Although this no nlinearity is nondeterministic, it is sufficient in principle to allow scalable linear optics quantum computation (LOQC). The most obvious way to encode a qubit optically is as a superposition of the vacuum and a single photon in one mode -- so-called "single-rail" logic. Until now this approach was thought to be prohibitively expensive (in resources) compared to "dual-rail" logic where a qubit is stored by a photon across two modes. Here we attack this problem with real-time feedback control, which can realize a quantum-limited phase measurement on a single mode, as has been recently demonstrated experimentally. We show that with this added measurement resource, the resource requirements for single-rail LOQC are not substantially different from those of dual-rail LOQC. In particular, with adaptive phase measurements an arbitrary qubit state $\alpha \ket{0} + \beta\ket{1}$ can be prepared deterministically

Properties of length-apodized phase-shifted lpgs operating at the phase matching turning point

The characteristics of length-apodized phase-shifted fiber optic long period gratings with full and partial nanostructured coatings have been explored theoretically and experimentally. The twin rejection bands that are characteristic of length-apodized phase-shifted long period gratings are studied for a long period grating (LPG) operating at the phase matching turning point. When one half of the length of the LPG is coated, complex bandgap like structure appears within the transmission spectrum, which may be of benefit to spectral filter design and for sensing applications

Error models for mode-mismatch in linear optics quantum computing

One of the most significant challenges facing the development of linear optics quantum computing (LOQC) is mode-mismatch, whereby photon distinguishability is introduced within circuits, undermining quantum interference effects. We examine the effects of mode-mismatch on the parity (or fusion) gate, the fundamental building block in several recent LOQC schemes. We derive simple error models for the effects of mode-mismatch on its operation, and relate these error models to current fault tolerant threshold estimates.Comment: 6 pages, 7 figure

Weak measurement and control of entanglement generation

In this paper we show how weak joint measurement and local feedback can be used to control entanglement generation between two qubits. To do this, we make use of a decoherence free subspace (DFS). Weak measurement and feedback can be used to drive the system into this subspace rapidly. Once within the subspace, feedback can generate entanglement rapidly, or turn off entanglement generation dynamically. We also consider, in the context of weak measurement, some of differences between purification and generating entanglement

The value of waiting: Russia's integration into the international capital markets

Capital flight has characterized the transformation process in Russia. Inflows of foreign direct investment have been minor and have been preceeded by inflows of portfolio capital. The paper shows that uncertainty about macroeconomic stabilization exhibits a strong negative effect on the volume of capital inflows when investment decisions are irreversible. Reducing uncertainty may but must not necessarily lead to more investment. The fact that monetary stabilization policies have not been accompanied by comprehensive institutional reforms can explain the pattern of Russia's capital flows in general and the dismal performance in attracting foreign direct investment in particular.

Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration