Deterministic and cascadable conditional phase gate for photonic qubits

Previous analyses of conditional \phi-phase gates for photonic qubits that treat cross-phase modulation (XPM) in a causal, multimode, quantum field setting suggest that a large (~\pi rad) nonlinear phase shift is always accompanied by fidelity-degrading noise [J. H. Shapiro, Phys. Rev. A 73, 062305 (2006); J. Gea-Banacloche, Phys. Rev. A 81, 043823 (2010)]. Using an atomic V-system to model an XPM medium, we present a conditional phase gate that, for sufficiently small nonzero \phi, has high fidelity. The gate is made cascadable by using using a special measurement, principal mode projection, to exploit the quantum Zeno effect and preclude the accumulation of fidelity-degrading departures from the principal-mode Hilbert space when both control and target photons illuminate the gate

Qudit-Basis Universal Quantum Computation using χ(2)\chi^{(2)} Interactions

We prove that universal quantum computation can be realized---using only linear optics and $\chi^{(2)}$ (three-wave mixing) interactions---in any $(n+1)$-dimensional qudit basis of the $n$-pump-photon subspace. First, we exhibit a strictly universal gate set for the qubit basis in the one-pump-photon subspace. Next, we demonstrate qutrit-basis universality by proving that $\chi^{(2)}$ Hamiltonians and photon-number operators generate the full $\mathfrak{u}(3)$ Lie algebra in the two-pump-photon subspace, and showing how the qutrit controlled-$Z$ gate can be implemented with only linear optics and $\chi^{(2)}$ interactions. We then use proof by induction to obtain our general qudit result. Our induction proof relies on coherent photon injection/subtraction, a technique enabled by $\chi^{(2)}$ interaction between the encoding modes and ancillary modes. Finally, we show that coherent photon injection is more than a conceptual tool in that it offers a route to preparing high-photon-number Fock states from single-photon Fock states.Comment: 9 pages, 3 figure

The Role of Law and Lawyers in Japan and the United States

The issues raised in connection with delivery of legal services in Japan are complex and best understood against the backdrop of the development of the legal profession in Japan. Part I of this article discusses the history of the Japanese legal profession, especially its recent history. Part II shows how this development has shaped the issues in the current dispute. It recounts the development of the dispute, the arguments that have been made on the Japanese and American sides, and the course of the negotiations over legal services as part of the Japan-U.S. trade agenda. This article concludes with a critical analysis of the recent Japanese proposals for regulating foreign legal consultants

Folding equilateral plane graphs

22nd International Symposium, ISAAC 2011, Yokohama, Japan, December 5-8, 2011. ProceedingsWe consider two types of folding applied to equilateral plane graph linkages. First, under continuous folding motions, we show how to reconfigure any linear equilateral tree (lying on a line) into a canonical configuration. By contrast, such reconfiguration is known to be impossible for linear (nonequilateral) trees and for (nonlinear) equilateral trees. Second, under instantaneous folding motions, we show that an equilateral plane graph has a noncrossing linear folded state if and only if it is bipartite. Not only is the equilateral constraint necessary for this result, but we show that it is strongly NP-complete to decide whether a (nonequilateral) plane graph has a linear folded state. Equivalently, we show strong NP-completeness of deciding whether an abstract metric polyhedral complex with one central vertex has a noncrossing flat folded state with a specified “outside region”. By contrast, the analogous problem for a polyhedral manifold with one central vertex (single-vertex origami) is only weakly NP-complete

Superfluidity of Σ−\Sigma^- hyperons in β\beta-stable neutron star matter

In this work we evaluate the $^1S_0$ energy gap of $\Sigma^-$ hyperons in $\beta$-stable neutron star matter. We solve the BCS gap equation for an effective $\Sigma^-\Sigma^-$ pairing interaction derived from the most recent parametrization of the hyperon-hyperon interaction constructed by the Nijmegen group. We find that the $\Sigma^-$ hyperons are in a $^1S_0$ superfluid state in the density region $\sim 0.27-0.7$ fm$^{-3}$, with a maximum energy gap of order 8 MeV at a total baryon number density of $\sim 0.37$ fm$^{-3}$ and a $\Sigma^-$ fraction of about 8%. We examine the implications on neutron star cooling.Comment: 4 pages, double column, 4 figures. Accepted in PR

Optimal Regulation in the Presence of Reputation Concerns

In all markets, firms go through a process of creative destruction: entry, random growth and exit. In many of these markets there are also regulations that restrict entry, possibly distorting this process. We study the public interest rationale for entry taxes in a general equilibrium model with free entry and exit of firms in which firm dynamics are driven by reputation concerns. In our model firms can produce high-quality output by making a costly but efficient initial unobservable investment. If buyers never learn about this investment, an extreme “lemons problem” develops, no firm invests, and the market shuts down. Learning introduces reputation incentives such that a fraction of entrants do invest. We show that, if the market operates with spot prices, entry taxes always enhance the role of reputation to induce investment, improving welfare despite the impact of these taxes on equilibrium prices and total productio

Diagnostic Dilemma of Small Incidentally Discovered Adrenal Masses: Role for 131 I-6β-Iodomethyl-norcholesterol Scintigraphy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42408/1/268-21-1-36_21n1p36.pd