Session U2: Invited Session: Hot Topics

Ultrafast Rotation of Light Fields Applied to Highly Non-Linear Optics

Femtosecond laser beams can exhibit spatio-temporal couplings (STC), i.e. a temporal dependence of their spatial properties, or vice versa. Although these couplings have long been considered as detrimental for high-intensity and ultrafast experiments, moderate and controlled STC provide a powerful means of controlling high-intensity laser-matter interactions [1]. This talk will first explain the basics of a particular STC, where the propagation direction of laser light rotates in time on the femtosecond time scale. Laser pulses with such ultrafast wavefront rotation can be used to generate attosecond pulses of light through non-linear optical processes. We show that these pulses, periodically generated in each laser cycle, can then be emitted in spatially separated beamlets [1]. This effects provides a new type of light sources called attosecond lighthouses [1,2], and can be exploited for ultrafast measurements with femtosecond resolution, in a scheme called photonic streaking [3]. \\[4pt] [1] Phys. Rev. Lett. 108, 113904 (2012).\\[0pt] [2] Nature Phot. 6, 829-833 (2012).\\[0pt] [3] Nature Phot. 7, 651-656 (2013).   

Generation of Atomic Fock States Using Rydberg Blockade

The Rydberg blockade mechanism is a general method to enable entanglement of atomic spins on micron distance scales, without requiring quantum control of the motional degrees of freedom. Entanglement arises by energetically forbidding the production of strongly interacting atomic pair states. Recent experiments by us and others have used blockade to demonstrate milestones such as CNOT gates and single-photon sources. We have recently used blockade to demonstrate collective Rabi flopping of 3-16 atom ensembles (M. Ebert et al., PRL \textbf{112}, 043602 (2014)). Using calibrated number measurements, we quantitatively confirm the expected sqrt(N) Rabi frequency enhancement within 4\%. Using sequences of collective pi-pulses we then produce 1- and 2- atom Fock states with fidelities of 62\% and 48\%, respectively. The 2-atom Fock state shows the collective Rabi flopping without corruption from atom number fluctuations. This work is supported by the NSF and the AFOSR Quantum Memories MURI.   

Quantum Dynamics of Many-body Spin Chains Using Atomic Ions

Quantum simulation, a field in which well-controlled quantum systems are used to study many-body physics that would otherwise be challenging to model, has undergone a great deal of progress in recent years. In particular, trapped ions have proven an excellent platform for simulating quantum magnetism, with their long-lived coherence times, tunable spin-spin interactions mediated by optical dipole forces, and ease of individual readout. The manipulation of more than 10 spins is now routine and has allowed the study of dynamics that will be difficult to simulate classically in larger systems, such as spectroscopy of excitation energies (arXiv 1401.5751) and the spread of spin correlations in a system with long-range interactions (arXiv 1401.5088). In the near future, we expect to apply these techniques to the study of a variety of phenomena such as prethermalization in an isolated quantum system, and to upgrade the apparatus so as to handle many tens of spins, a system size well beyond what is classically calculable.   

Magneto-optical Trapping of a Diatomic Molecule

The magneto-optical trap (MOT) is the workhorse technique for atomic physics in the ultracold regime, serving as the starting point in applications from optical clocks to quantum-degenerate gases. Although MOTs have been used with a wide array of atomic species, realization of a molecular MOT was long considered infeasible. In this talk we will describe the first magneto-optical trap for a molecule, strontium monofluoride (SrF). Our MOT produces the coldest trapped sample of directly-cooled molecules to date, with temperature T $\sim$2.5 mK. The SrF MOT is loaded from a cryogenic buffer-gas beam slowed by laser radiation pressure. Images of laser-induced fluorescence allow us to characterize the trap's properties. Although magneto-optical trapping of diatomic molecules is in its infancy, our results indicate that access to the ultracold regime may be possible for several molecular species, with potential applications from quantum simulation to tests of fundamental symmetries to ultracold chemistry.