Floquet Analysis of Atom Optics Tunneling Experiments

Dynamical tunneling has been observed in atom optics experiments by two groups. We show that the experimental results are extremely well described by time-periodic Hamiltonians with momentum quantized in units of the atomic recoil. The observed tunneling has a well defined period when only two Floquet states dominate the dynamics. Beat frequencies are observed when three Floquet states dominate. We find frequencies which match those observed in both experiments. The dynamical origin of the dominant Floquet states is identified.Comment: Accepted in Physical Review

Exhumation history of eastern Ladakh revealed by Ar-40/Ar-39 and fission-track ages: the Indus River-Tso Morari transect, NW Himalaya

Fission-track and Ar-40/Ar-39 ages place time constraints on the exhumation of the North Himalayan nappe stack, the Indus Suture Zone and Molasse, and the Transhimalayan Batholith in eastern Ladakh (NW India). Results from this and previous studies on a north-south transect passing near Tso Morari Lake suggest that the SW-directed North Himalayan nappe stack (comprising the Mata, Tetraogal and Tso Morari nappes) was emplaced and metamorphosed by c. 50-45 Ma, and exhumed to moderately shallow depths (c. 10 km) by c. 45-40 Ma. From the mid-Eocene to the present, exhumation continued at a steady and slow rate except for the root zone of the Tso Morari nappe, which cooled faster than the rest of the nappe stack. Rapid cooling occurred at c. 20 Ma and is linked to brittle deformation along the normal Ribil-Zildat Fault concomitant with extrusion of the Crystalline nappe in the south. Data from the Indus Molasse suggest that sediments were still being deposited during the Miocene

Structural and dynamical aspects of avoided-crossing resonances in a 33-level Λ\Lambda system

In a recent publication [Phys. Rev. A 79, 065602 (2009)] it was shown that an avoided-crossing resonance can be defined in different ways, according to level-structural or dynamical aspects, which do not coincide in general. Here a simple $3$-level system in a $\Lambda$ configuration is discussed, where the difference between both definitions of the resonance may be observed. We also discuss the details of a proposed experiment to observe this difference, using microwave fields coupling hyperfine magnetic sublevels in alkali atoms.Comment: 7 pages, 5 figure

Feedback cooling of atomic motion in cavity QED

We consider the problem of controlling the motion of an atom trapped in an optical cavity using continuous feedback. In order to realize such a scheme experimentally, one must be able to perform state estimation of the atomic motion in real time. While in theory this estimate may be provided by a stochastic master equation describing the full dynamics of the observed system, integrating this equation in real time is impractical. Here we derive an approximate estimation equation for this purpose, and use it as a drive in a feedback algorithm designed to cool the motion of the atom. We examine the effectiveness of such a procedure using full simulations of the cavity QED system, including the quantized motion of the atom in one dimension.Comment: 22 pages, 17 figure

A diode laser stabilization scheme for 40Ca+ single ion spectroscopy

We present a scheme for stabilizing multiple lasers at wavelengths between 795 and 866 nm to the same atomic reference line. A reference laser at 852 nm is stabilized to the Cs D2 line using a Doppler-free frequency modulation technique. Through transfer cavities, four lasers are stabilized to the relevant atomic transitions in 40Ca+. The rms linewidth of a transfer-locked laser is measured to be 123 kHz with respect to an independent atomic reference, the Rb D1 line. This stability is confirmed by the comparison of an excitation spectrum of a single 40Ca+ ion to an eight-level Bloch equation model. The measured Allan variance of 10^(-22) at 10 s demonstrates a high degree of stability for time scales up to 100 s.Comment: 8 pages, 11 figure

Quantum feedback control of atomic motion in an optical cavity

We study quantum feedback cooling of atomic motion in an optical cavity. We design a feedback algorithm that can cool the atom to the ground state of the optical potential with high efficiency despite the nonlinear nature of this problem. An important ingredient is a simplified state-estimation algorithm, necessary for a real-time implementation of the feedback loop. We also describe the critical role of parity dynamics in the cooling process and present a simple theory that predicts the achievable steady-state atomic energies

Magnetometer suitable for Earth field measurement based on transient atomic response

We describe the development of a simple atomic magnetometer using $^{87}$Rb vapor suitable for Earth magnetic field monitoring. The magnetometer is based on time-domain determination of the transient precession frequency of the atomic alignment around the measured field. A sensitivity of 1.5 nT/$\sqrt{Hz}$ is demonstrated on the measurement of the Earth magnetic field in the laboratory. We discuss the different parameters determining the magnetometer precision and accuracy and predict a sensitivity of 30 pT/$\sqrt{Hz}$Comment: 6 pages, 5 figure

Nonlinear metrology with a quantum interface

We describe nonlinear quantum atom-light interfaces and nonlinear quantum metrology in the collective continuous variable formalism. We develop a nonlinear effective Hamiltonian in terms of spin and polarization collective variables and show that model Hamiltonians of interest for nonlinear quantum metrology can be produced in $^{87}$Rb ensembles. With these Hamiltonians, metrologically relevant atomic properties, e.g. the collective spin, can be measured better than the "Heisenberg limit" $\propto 1/N$. In contrast to other proposed nonlinear metrology systems, the atom-light interface allows both linear and non-linear estimation of the same atomic quantities.Comment: 8 pages, 1 figure