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.