Engineering Fast High-Fidelity Quantum Operations With Constrained Interactions

Understanding how to tailor quantum dynamics to achieve a desired evolution is a crucial problemin almost all quantum technologies. We present a very general method for designing high-efficiencycontrol sequences that are always fully compatible with experimental constraints on available inter-actions and their tunability. Our approach reduces in the end to finding control fields by solvinga set of time-independent linear equations. We illustrate our method by applying it to a numberof physically-relevant problems: the strong-driving limit of a two-level system, fast squeezing in aparametrically driven cavity, the leakage problem in transmon qubit gates, and the acceleration ofSNAP gates in a qubit-cavity system

Congressional Control of the Courts: A Theoretical and Empirical Analysis of Expansion of the Federal Judiciary

Congress has many available tools to influence the federal judiciary. In this article, we consider Congress\u27 ability to balance, or stack, the courts through the creation of federal judgeships. While caseload pressure often produces the need for more judgeships, we demonstrate that political party alignment between Congress and the president often determines the timing of the judicial expansion. The net effect of expanding during political alignment is to speed up changes in the political balance of the judiciary in favor of the current Congress. We also examine the determinants of expansion size and show that both political alignment and caseload pressure influence Congress\u27 decision regarding how many judgeships to add

The Structure and Conduct of Corporate Lobbying: How Firms Lobby the Federal Communications Commission

lobbying (internal organization vs. trade association) by firms in administrative agencies. It explores the power and limitations of the collective action theories and transaction cost theories in explaining lobbying. It introduces a dataset of over 900 lobbying contacts cover 101 issues at the Federal Communications Commission (FCC) in early 1998. We find that the structure and conduct of large firm lobbying at the FCC is consistent with the predictions of theories of transaction costs and the main results of theories of collective action. However, large firms do not change their behavior drastically as structures arise to remedy the free rider problem. Small firms show no sensitivity to collective action issues or transaction cost issues in the organization or amount of their lobbying, but they do lobby less when having to reveal proprietary information. In sum, large firms behave largely consistent with theoretical predictions, while small firms do not.

Edge-colouring and total-colouring chordless graphs

A graph $G$ is \emph{chordless} if no cycle in $G$ has a chord. In the present work we investigate the chromatic index and total chromatic number of chordless graphs. We describe a known decomposition result for chordless graphs and use it to establish that every chordless graph of maximum degree $\Delta\geq 3$ has chromatic index $\Delta$ and total chromatic number $\Delta + 1$. The proofs are algorithmic in the sense that we actually output an optimal colouring of a graph instance in polynomial time

Complexity of colouring problems restricted to unichord-free and \{square,unichord\}-free graphs

A \emph{unichord} in a graph is an edge that is the unique chord of a cycle. A \emph{square} is an induced cycle on four vertices. A graph is \emph{unichord-free} if none of its edges is a unichord. We give a slight restatement of a known structure theorem for unichord-free graphs and use it to show that, with the only exception of the complete graph $K_4$, every square-free, unichord-free graph of maximum degree~3 can be total-coloured with four colours. Our proof can be turned into a polynomial time algorithm that actually outputs the colouring. This settles the class of square-free, unichord-free graphs as a class for which edge-colouring is NP-complete but total-colouring is polynomial

Wireless interrogation of an optically modulated resonant tunnelling diode oscillator

n this work, a resonant tunnelling diode-photo-detector based microwave oscillator is amplitude modulated using an optical signal. The modulated free running oscillator is coupled to an antenna and phase locked by a wireless carrier that allows remote extraction of the information contained in the modulation. An off-the-shelf demodulator has been used to recover the envelope of the baseband data originally contained in the optical signal. Data were successfully transmitted at a rate of 1 MSym/s with a bit error rate below 10−6

Enhancement of the nonlinear optical absorption of the E7 liquid crystal at the nematic-isotropic transition

We present an experimental study of the nonlinear optical absorption of the eutectic mixture E7 at the nematic-isotropic phase transition by the Z-scan technique, under a continuos wave excitation at 532 nm. In the nematic region, the effective nonlinear optical coefficient \beta for an extraordinary beam is negative and for an ordinary beam is positive, being null in the isotropic phase. The parameter S_{NL} defined in terms of the nonlinear absorption coefficients in a similar way than the optical order parameter from the linear dichoic ratio behavies like an order parameter with a critical exponent 0.22+-0.05, in good agreement with the tri-critical hipothesis of the N-I transition.Comment: 11 pages, 6 figures, to be published in the vol 42 of the Brazilian Jurnal of physic