A search for chiral asymmetry in secondary electron emission from cysteine induced by longitudinally polarized electrons

We performed experiments searching for chirality-dependent secondary electron emission for a 141 eV longitudinally spin-polarized electron beam incident on a thick solid cysteine target. We determined the secondary electron yield by measuring the positive current produced when the cysteine target was negatively biased. No spin-dependent effects to a level of 10−3 were found for the secondary electron emission yield

Transverse measurements of polarization in optically pumped Rb vapor cells

We have developed a simple heuristic method for determining the polarization of an optically pumped alkalimetal vapor. A linearly polarized probe beam traverses a vapor cell perpendicular to the pump-beam propagation direction, and the transmitted beam intensity is monitored for orthogonal linear polarizations. As the probe beam is scanned in frequency across the D1 transition, its linear-polarization-dependent transmission can be used as a measure of the atomic orientation of the vapor. We analyze these transmission differences and their dependence on the alkali-metal number density in the vapor

An improved source of spin-polarized electrons based on spin exchange in optically pumped rubidium vapor

We have improved a polarized electron source in which unpolarized electrons undergo collisions with a mixture of buffer gas molecules and optically spin-polarized Rb atoms. With a nitrogen buffer gas, the source reliably provides spin polarization between 15% and 25% with beam currents \u3e4 μA. Vacuum pump upgrades mitigate problems caused by denatured diffusion pump oil, leading to longer run times. A new differential pumping scheme allows the use of higher buffer gas pressures up to 800 mTorr. With a new optics layout, the Rb polarization is continuously monitored by a probe laser and improved pump laser power provides more constant high polarization. We have implemented an einzel lens to better control the energy of the electrons delivered to the target chamber and to preferentially select electron populations of higher polarization. The source is designed for studies of biologically relevant chiral molecule samples, which can poison photoemission-based GaAs polarized electron sources at very low partial pressures. It operates adjacent to a target chamber that rises to pressures as high as 10−4 Torr and has been implemented in a first experiment with chiral cysteine targets

Optically pumped spin-exchange polarized-electron source

We describe the operation of a prototype polarized-electron source. Rubidium vapor, contained in a cell, is optically pumped in the presence of a buffer gas. Unpolarized electrons from a tungsten filament are injected into the cell and extracted after undergoing spin exchange with the Rb atoms. We compare the performance of the source when different buffer gases are used. We measure a decrease in electron polarization as their injection energy increases, but find an unexpected regime at higher injection energies yielding increased electron polarization accompanied by a 40-fold increase in current, suggesting the production of slow secondary electrons in the target cell. With ethylene, we have measured electron currents of 4 μA simultaneously with electron polarizations of 24%. This work offers the promise of a simple, benchtop, “turnkey” source of polarized electrons

The Los Alamos Trapped Ion Quantum Computer Experiment

The development and theory of an experiment to investigate quantum computation with trapped calcium ions is described. The ion trap, laser and ion requirements are determined, and the parameters required for quantum logic operations as well as simple quantum factoring are described.Comment: 41 pages, 16 figures, submitted to Fortschritte der Physi

Characterizing the spin state of an atomic ensemble using the magneto-optical resonance method

Quantum information protocols utilizing atomic ensembles require preparation of a coherent spin state (CSS) of the ensemble as an important starting point. We investigate the magneto-optical resonance method for characterizing a spin state of cesium atoms in a paraffin coated vapor cell. Atoms in a constant magnetic field are subject to an off-resonant laser beam and an RF magnetic field. The spectrum of the Zeeman sub-levels, in particular the weak quadratic Zeeman effect, enables us to measure the spin orientation, the number of atoms, and the transverse spin coherence time. Notably the use of 894nm pumping light on the D1-line, ensuring the state F=4, m_F=4 to be a dark state, helps us to achieve spin orientation of better than 98%. Hence we can establish a CSS with high accuracy which is critical for the analysis of the entangled states of atoms.Comment: 12 pages ReVTeX, 6 figures, in v2 added ref. and corrected typo

Observation of power-law scaling for phase transitions in linear trapped ion crystals

We report an experimental confirmation of the power-law relationship between the critical anisotropy parameter and ion number for the linear-to-zigzag phase transition in an ionic crystal. Our experiment uses laser cooled calcium ions confined in a linear radio-frequency trap. Measurements for up to 10 ions are in good agreement with theoretical and numeric predictions. Implications on an upper limit to the size of data registers in ion trap quantum computers are discussed.Comment: Physical Review Letters in press, 4 pages, 4 figure

Coupling an optical trap to a mass separator

The efficient coupling of a magneto-optical trap to a mass separator is being developed to undertake high-precision electroweak interaction measurements in a series of radioisotopes. The use of ion implantation and subsequent heated-foil release is being pursued as a suitable way of introducing radioactive samples into the ultrahigh vacuum region of an optical trap without gas loading. This paper discusses the layout of the mass separator,the coupling to a magneto- optical trap, and the implantation and release scheme