Topics in Quantum Computers

I provide an introduction to quantum computers, describing how they might be realized using language accessible to a solid state physicist. A listing of the minimal requirements for creating a quantum computer is given. I also discuss several recent developments in the area of quantum error correction, a subject of importance not only to quantum computation, but also to some aspects of the foundations of quantum theory.Comment: 22 pages, Latex, 1 eps figure, Paper to be published in "Mesoscopic Electron Transport", edited by L. Kowenhoven, G. Schoen and L. Sohn, NATO ASI Series E, Kluwer Ac. Publ., Dordrecht. v2: typos in refrences fixe

Observing Majorana bound states of Josephson vortices in topological superconductors

In recent years there has been an intensive search for Majorana fermion states in condensed matter systems. Predicted to be localized on cores of vortices in certain non-conventional superconductors, their presence is known to render the exchange statistics of bulk vortices non-Abelian. Here we study the equations governing the dynamics of phase solitons (fluxons) in a long Josephson junction in a topological superconductor. We show that the fluxon will bind a localized zero energy Majorana mode and will consequently behave as a non-Abelian anyon. The low mass of the fluxon, as well as its experimentally observed quantum mechanical wave-like nature, will make it a suitable candidate for vortex interferometry experiments demonstrating non-Abelian statistics. We suggest two experiments that may reveal the presence of the zero mode carried by the fluxon. Specific experimental realizations will be discussed as well.Comment: 10 pages, 3 figures, published version (title modified

nu=1/2 quantum Hall effect in the Aharonov-Casher geometry in a mesoscopic ring

We study the effect of an electric charge in the middle of a ring of electrons in a magnetic field such as $\nu = 1/2$. In the absence of the central charge, a residual current should appear due to an Aharanov-Bohm effect. As the charge varies, periodic currents should appear in the ring. We evaluate the amplitude of these currents, as well as their period as the central charge varies. The presence of these currents should be a direct signature of the existence of a statistical gauge field in the $\nu=1/2$ quantum Hall effect. Numerical diagonalizations for a small number of electrons on the sphere are also carried out. The numerical results up to 9 electrons are qualitatively consistent with the mean field picture.Comment: 23 pages,14 included postscript figures, submitted to Phys. Rev.

Possible realization of Josephson charge qubits in two coupled Bose-Einstein condensates

We demonstrate that two coupled Bose-Einstein condensates (BEC) at zero temperature can be used to realize a qubit which is the counterpart of Josephson charge qubits. The two BEC are weakly coupled and confined in an asymmetric double-well trap. When the "charging energy" of the system is much larger than the Josephson energy and the system is biased near a degeneracy point, the two BEC represent a qubit with two states differing only by one atom. The realization of the BEC qubits in realistic BEC experiments is briefly discussed.Comment: 4 pages; comments are welcome / Corrected typos in Eq. (16); a note adde

Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast

Acknowledgments We thank Rebecca Shapiro for creating CaLC1819, CaLC1855 and CaLC1875, Gillian Milne for help with EM, Aaron Mitchell for generously providing the transposon insertion mutant library, Jesus Pla for generously providing the hog1 hst7 mutant, and Cathy Collins for technical assistance.Peer reviewedPublisher PD

HIV policy: the path forward--a joint position paper of the HIV Medicine Association of the Infectious Diseases Society of America and the American College of Physicians.

Executive Summary The American College of Physicians (ACP) and the Infectious Diseases Society of America (IDSA) have jointly published 3 policy statements on AIDS, the first in 1986 [1], the second in 1988 [2], and the third in 1994 [3]. In 2001, the IDSA created the HIV Medicine Association (HIVMA), and this updated policy paper is a collaboration between the ACP and the HIVMA of the IDSA. Since the last statement, many new developments call for the need to reexamine and update our policies relating to HIV infection. First, there have been major advances in treatment for HIV infection that have transformed HIV/AIDS from a terminal illness to a chronic disease for many of those who have access to potent therapies and expert medical care [4]. Second, there has been a profound expansion and intensification of the global HIV pandemic, particularly in sub-Saharan Africa, coupled with significant US leadership and resources aimed at providing prevention and care services to affected populations in developing countries. Third, the concerns that were prevalent in the mid-1990s regarding the possibility of HIV transmission in health care settings have ultimately proven to be unfounded as the result of the adoption of universal precautions in those settings. In this article, we emphasize the public health and clinical imperatives for earlier identification of persons with HIV infection; the urgent need to expand access to state-of-the-art HIV care and treatment for infected individuals; the need for access to comprehensive prevention and education for those living with and those at risk for HIV infection; and the need for stronger national leadership to respond to the HIV epidemic in the United States and in the developing world. In December 2008, the ACP and HIVMA released a guidance statement on screening for HIV infection in health care settings that recommended that clinicians adopt routine screening for HIV infection and encourage patients to be tested. Also included in the guidance statement is a recommendation that clinicians determine the need for additional screening on an individual basis

Antimalarial Iron Chelator, FBS0701, Shows Asexual and Gametocyte Plasmodium falciparum Activity and Single Oral Dose Cure in a Murine Malaria Model

Iron chelators for the treatment of malaria have proven therapeutic activity in vitro and in vivo in both humans and mice, but their clinical use is limited by the unsuitable absorption and pharmacokinetic properties of the few available iron chelators. FBS0701, (S)3”-(HO)-desazadesferrithiocin-polyether [DADFT-PE], is an oral iron chelator currently in Phase 2 human studies for the treatment of transfusional iron overload. The drug has very favorable absorption and pharmacokinetic properties allowing for once-daily use to deplete circulating free iron with human plasma concentrations in the high µM range. Here we show that FBS0701 has inhibition concentration 50% (IC50) of 6 µM for Plasmodium falciparum in contrast to the IC50 for deferiprone and deferoxamine at 15 and 30 µM respectively. In combination, FBS0701 interfered with artemisinin parasite inhibition and was additive with chloroquine or quinine parasite inhibition. FBS0701 killed early stage P. falciparum gametocytes. In the P. berghei Thompson suppression test, a single dose of 100 mg/kg reduced day three parasitemia and prolonged survival, but did not cure mice. Treatment with a single oral dose of 100 mg/kg one day after infection with 10 million lethal P. yoelii 17XL cured all the mice. Pretreatment of mice with a single oral dose of FBS0701 seven days or one day before resulted in the cure of some mice. Plasma exposures and other pharmacokinetics parameters in mice of the 100 mg/kg dose are similar to a 3 mg/kg dose in humans. In conclusion, FBS0701 demonstrates a single oral dose cure of the lethal P. yoelii model. Significantly, this effect persists after the chelator has cleared from plasma. FBS0701 was demonstrated to remove labile iron from erythrocytes as well as enter erythrocytes to chelate iron. FBS0701 may find clinically utility as monotherapy, a malarial prophylactic or, more likely, in combination with other antimalarials