Experimental study of optimal measurements for quantum state tomography

Quantum tomography is a critically important tool to evaluate quantum hardware, making it essential to develop optimized measurement strategies that are both accurate and efficient. We compare a variety of strategies using nearly pure test states. Those that are informationally complete for all states are found to be accurate and reliable even in the presence of errors in the measurements themselves, while those designed to be complete only for pure states are far more efficient but highly sensitive to such errors. Our results highlight the unavoidable tradeoffs inherent to quantum tomography.Comment: 5 pages, 3 figure

Quantum computing with spatially delocalized qubits

We analyze the operation of quantum gates for neutral atoms with qubits that are delocalized in space, i.e., the computational basis states are defined by the presence of a neutral atom in the ground state of one out of two trapping potentials. The implementation of single qubit gates as well as a controlled phase gate between two qubits is discussed and explicit calculations are presented for rubidium atoms in optical microtraps. Furthermore, we show how multi-qubit highly entangled states can be created in this scheme.Comment: 4 pages, 4 figure

Optical Lattice Polarization Effects on Hyperpolarizability of Atomic Clock Transitions

The light-induced frequency shift due to the hyperpolarizability (i.e. terms of second-order in intensity) is studied for a forbidden optical transition, $J$=0$\to$$J$=0. A simple universal dependence on the field ellipticity is obtained. This result allows minimization of the second-order light shift with respect to the field polarization for optical lattices operating at a magic wavelength (at which the first-order shift vanishes). We show the possibility for the existence of a magic elliptical polarization, for which the second-order frequency shift vanishes. The optimal polarization of the lattice field can be either linear, circular or magic elliptical. The obtained results could improve the accuracy of lattice-based atomic clocks.Comment: 4 pages, RevTeX4, 2 eps fig

Ultrastable Optical Clock with Neutral Atoms in an Engineered Light Shift Trap

An ultrastable optical clock based on neutral atoms trapped in an optical lattice is proposed. Complete control over the light shift is achieved by employing the $5s^2 {}^1S_0 \to 5s5p {}^3P_0$ transition of ${}^{87}{\rm Sr}$ atoms as a "clock transition". Calculations of ac multipole polarizabilities and dipole hyperpolarizabilities for the clock transition indicate that the contribution of the higher-order light shifts can be reduced to less than 1 mHz, allowing for a projected accuracy of better than $10^{-17}$.Comment: 4 pages, 2 figures, accepted for publication in Phys. Rev. Let

Superfluid Fermi gas in a 1D optical lattice

We calculate the superfluid transition temperature for a two-component 3D Fermi gas in a 1D tight optical lattice and discuss a dimensional crossover from the 3D to quasi-2D regime. For the geometry of finite size discs in the 1D lattice, we find that even for a large number of atoms per disc, the critical effective tunneling rate for a quantum transition to the Mott insulator state can be large compared to the loss rate caused by three-body recombination. This allows the observation of the Mott transition, in contrast to the case of Bose-condensed gases in the same geometry.Comment: 4 pages, 1 figur

Prevalence of Cardiovascular Risk Factors among Young Adults (18-25 Years) in Mozambique

The life course development of cardiovascular diseases (CVDs) and the undergoing epidemiological transition in Mozambique highlight the importance of monitoring the cardiovascular risk profile in young adults. Therefore, this study aims to estimate the prevalence of CVD risk factors in a population aged 1825 years living in Mozambique. A total of 776 young adults from a nationally representative sample were evaluated in 2014/2015 following the World Health Organizations STEPwise approach to chronic disease risk factor surveillance. Current smoking was the most prevalent among rural men (10.8%, 95%CI: 6.317.8), and drinking was most prevalent among urban men (38.6%, 95%CI: 29.348.8). The proportion of young adults not engaging in at least 75 min of vigorous physical activity per week ranged between 14.5% in rural men and 61.6% in urban women. The prevalence of being overweight/obese and hypertension were highest among urban women (21.6%, 95%CI: 14.730.6) and urban men (25.2%, 95%CI: 15.937.6), respectively. Education >8 years (vs. none) was independently associated with lower odds of being a current smoker, and increased monthly household income was associated with increased odds of low levels of physical activity. This study shows that important CVD risk factors are already common in the young adult population of Mozambique.</jats:p