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.

Demonstration of Two-Atom Entanglement with Ultrafast Optical Pulses.

We demonstrate quantum entanglement of two trapped atomic ion qubits using a sequence of ultrafast laser pulses. Unlike previous demonstrations of entanglement mediated by the Coulomb interaction, this scheme does not require confinement to the Lamb-Dicke regime and can be less sensitive to ambient noise due to its speed. To elucidate the physics of an ultrafast phase gate, we generate a high entanglement rate using just ten pulses, each of ∼20 ps duration, and demonstrate an entangled Bell state with (76±1)% fidelity. These results pave the way for entanglement operations within a large collection of qubits by exciting only local modes of motion.

Suppressing the loss of ultracold molecules via the continuous quantum Zeno effect.

We investigate theoretically the suppression of two-body losses when the on-site loss rate is larger than all other energy scales in a lattice. This work quantitatively explains the recently observed suppression of chemical reactions between two rotational states of fermionic KRb molecules confined in one-dimensional tubes with a weak lattice along the tubes [Yan et al., Nature (London) 501, 521 (2013)]. New loss rate measurements performed for different lattice parameters but under controlled initial conditions allow us to show that the loss suppression is a consequence of the combined effects of lattice confinement and the continuous quantum Zeno effect. A key finding, relevant for generic strongly reactive systems, is that while a single-band theory can qualitatively describe the data, a quantitative analysis must include multiband effects. Accounting for these effects reduces the inferred molecule filling fraction by a factor of 5. A rate equation can describe much of the data, but to properly reproduce the loss dynamics with a fixed fillingfraction for all lattice parameters we develop a mean-field model and benchmark it with numerically exacttime-dependent density matrix renormalization group calculations.

Anisotropic polarizability of ultracold polar 40K87Rb molecules.

We report the measurement of the anisotropic ac polarizability of ultracold polar (40)K(87)Rb molecules in the ground and first rotationally excited states. Theoretical analysis of the polarizability agrees well with experimental findings. Although the polarizability can vary by more than 30%, a "magic" angle between the laser polarization and the quantization axis is found where the polarizability of the |N=0,m(N)=0> and the |N=1,m(N)=0> states match. At this angle, rotational decoherence due to the mismatch in trapping potentials is eliminated, and we observe a sharp increase in the coherence time. This paves the way for precise spectroscopic measurements and coherent manipulations of rotational states as a tool in the creation and probing of novel quantum many-body states of polar molecules.

Clastogenicity of PvuII and EcoRI in electroporated CHO cells assayed by metaphase chromosomal aberrations and by micronuclei using the cytokinesis-block technique.

The clastogenicity of two restriction endonucleases with almost equal cutting frequencies: PvuII, generating blunt-ended DNA double-strand breaks (dsb) and EcoRI, generating cohesive-ended dsb, has been measured after treatment of electroporated CHO cells with these enzymes. Chromosome damage was assessed by the micronucleus cytokinesis-block technique, and for certain electroporation voltages by analysis of metaphase preparations. As has been found in previous studies, PvuII was found to be more effective in causing chromosomal damage than EcoRI, indicating the greater importance of blunt-ended dsb in chromosome aberration induction. These findings also validate the use of the micronucleus cytokinesis-block technique for evaluating chromosomal damage from restriction endonucleases. The results show a biphasic induction of micronuclei in binucleate cells as a function of time after treatment. This pattern is interpreted as indicating variable sensitivity of cells to restriction endonucleases at different stages of the cell cycle. The micronucleus data show that late collection times (40-48 h after treatment) give higher frequencies than short times. Both micronucleus and metaphase aberration data indicate that voltages in excess of 260 V are more efficient in porating cells than lower voltages and, as a result, lower restriction endonuclease concentrations could be used.

The fallacy of impoverishment.

Several recent studies have challenged the assumption that Medicaid requires impoverishment. Although two-thirds of the elderly poor are not covered by Medicaid, many nursing home Medicaid recipients retain sizeable assets, which pass to their heirs without repayment of public costs. The magnitude of asset spenddown is much smaller than previously believed. This article discusses these findings and explores their significance to the long-term care financing crisis.