Demonstration of the trapped-ion quantum CCD computer architecture.

The trapped-ion quantum charge-coupled device (QCCD) proposal1,2 lays out a blueprint for a universal quantum computer that uses mobile ions as qubits. Analogous to a charge-coupled device (CCD) camera, which stores and processes imaging information as movable electrical charges in coupled pixels, a QCCD computer stores quantum information in the internal state of electrically charged ions that are transported between different processing zones using dynamic electric fields. The promise of the QCCD architecture is to maintain the low error rates demonstrated in small trapped-ion experiments3-5 by limiting the quantum interactions to multiple small ion crystals, then physically splitting and rearranging the constituent ions of these crystals into new crystals, where further interactions occur. This approach leverages transport timescales that are fast relative to the coherence times of the qubits, the insensitivity of the qubit states of the ion to the electric fields used for transport, and the low crosstalk afforded by spatially separated crystals. However, engineering a machine capable of executing these operations across multiple interaction zones with low error introduces many difficulties, which have slowed progress in scaling this architecture to larger qubit numbers. Here we use a cryogenic surface trap to integrate all necessary elements of the QCCD architecture-a scalable trap design, parallel interaction zones and fast ion transport-into a programmable trapped-ion quantum computer that has a system performance consistent with the low error rates achieved in the individual ion crystals. We apply this approach to realize a teleported CNOT gate using mid-circuit measurement6, negligible crosstalk error and a quantum volume7 of 26 = 64. These results demonstrate that the QCCD architecture provides a viable path towards high-performance quantum computers.

Spectroscopic analysis of N-intrashell transitions in Rb-like to Ni-like Yb ions.

Extreme ultraviolet spectra of highly-charged ytterbium ions produced in an electron beam ion trap at the National Institute of Standards and Technology were observed with a flat-field grazing incidence spectrometer in the wavelength region of about 4 nm-20 nm. The measured spectra were interpreted through detailed analysis by collisional-radiative modeling of the non-Maxwellian EBIT plasma. Seventy-nine new spectral lines due to intrashell (Δn = 0, n = 4) electric-dipole, magnetic-dipole, and electric-quadrupole transitions were identified in Rb-like Yb33+ through Ni-like Yb42+ ions. The effects of strong configuration interaction within the n = 4 complex on the measured spectra are discussed for a number of ionization stages.

Measuring the difference in nuclear charge radius of Xe isotopes by EUV spectroscopy of highly charged Na-like ions.

The difference in the mean-square nuclear charge radius of xenon isotopes was measured utilizing a method based on extreme ultraviolet spectroscopy of highly charged Na-like ions. The isotope shift of the Na-like D1 (3s 2 S 1/2 - 3p 2 P 1/2) transition between the 124Xe and 136Xe isotopes was experimentally determined using the electron-beam ion-trap facility at the National Institute of Standards and Technology. The mass-shift and the field-shift coefficients were calculated with enhanced precision by the relativistic many-body perturbation theory and multiconfiguration Dirac-Hartree-Fock method. The mean-square nuclear charge radius difference was found to be δ〈r 2〉136,124 = 0.269(42) fm2. Our result has smaller uncertainty than previous experimental results and agrees with the literature values.

Anomalously Large Chiral Sensitivity in the Dissociative Electron Attachment of 10-Iodocamphor.

We have studied dissociative electron attachment (DEA) between low energy (≤0.6 eV) longitudinally polarized electrons and gas-phase chiral targets of 3-bromocamphor (C_{10}H_{15}BrO), 3-iodocamphor (C_{10}H_{15}IO), and 10-iodocamphor. The DEA rate depends on the sign of the incident electron helicity for a given target handedness, and it varies with both the atomic number (Z) and location of the heaviest atom in the molecule. While simple dynamic mechanisms can account for the asymmetry dependence on Z, they fail to explain the large asymmetry variation with the heavy atom location.

New technique for the reduction of helicity-correlated instrumental asymmetries in photoemitted beams of spin-polarized electrons.

We present a new optical system that significantly reduces helicity-dependent instrumental intensity asymmetries. It is an extension of a previous scheme [Appl. Opt.47, 2465 (2008)], where one laser beam is split using a polarizing beam splitter into two with orthogonal linear polarizations. The beams are sent through a chopper, allowing only one to pass at a time. The two temporally separated beams are then spatially recombined using a second beam splitter. A liquid crystal retarder preceding the first beam splitter controls the relative intensity of the two oppositely polarized beams, allowing reduction of instrumental asymmetries. This system has been modified to include a spatial filter and a Pockels cell placed after the second beam splitter to act as a second active polarization element. Using this method, we can control instrumental asymmetries to ∼5×10(-7) in 1 h of data taking, which is comparable to the precision achieved in "second-generation" high energy electron-nuclear scattering parity violation experiments.

Chirally sensitive electron-induced molecular breakup and the Vester-Ulbricht hypothesis.

We have studied dissociative electron attachment in sub-eV collisions between longitudinally polarized electrons and chiral bromocamphor molecules. For a given target enantiomer, the dissociative Br anion production depends on the helicity of the incident electrons, with an asymmetry that depends on the electron energy and is of order 3×10^{-4}. The existence of chiral sensitivity in a well-defined molecular breakup reaction demonstrates the viability of the Vester-Ulbrict hypothesis, namely, that the longitudinal polarization of cosmic beta radiation was responsible for the origins of biological homochirality.