No abstract

To isolate individual neutral atoms in microtraps, experimenters have long harnessed molecular photoassociation to make atom distributions sub-poissonian. While a variety of approaches have used a combination of attractive (red-detuned) and repulsive (blue-detuned) molecular states, todate all experiments have been predicated on red-detuned cooling. In our work, we present a shifted perspective -namely, the efficient way to capture single atoms is to eliminate red-detuned light in the loading stage, and use blue-detuned light that both cools the atoms and precisely controls trap loss through the amount of energy released during atom-atom collisions in the photoassociation process. Subsequent application of red-detuned light then assures the preparation of maximally one atom in the trap. Using Λ-enhanced grey molasses for loading, we study and model the molecular processes and find we can trap single atoms with 90% probability even in a very shallow optical tweezer. Using 100 traps loaded with 80% probability, we demonstrate one example of the power of enhanced loading by assembling a grid of 36 atoms using only a single move of rows and columns in 2D. Our insight will be key in scaling the number of particles in bottom-up quantum simulation and computation with atoms, or even molecules.

The fie ld of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, d iff iculty ex ists in u sin g deep sub mergence vehicle man ipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates.We have developed, tested, and successfully deployed by remotely operated vehicle (RO V) a precision underwater positioner (P UP ) which provides the stability and precision movement required to perform spectroscopic measurements usin g the Deep Ocean In Situ Spectrometer (DORISS) instru ment on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positionin g on the seafloor. P UP is capable of translating the DORI SS optical head with a precision of 0.1 mm in three dimension s over a range of at least 15 cm, at depths up to 4000 m, and under the nor mal range of oceanic conditions (T, P , current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. Th is capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, includ in g the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral gra ins. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.

We demonstrate the ability to extract a spin-entangled state of two neutral atoms via postselection based on a measurement of their spatial configuration. Typically, entangled states of neutral atoms are engineered via atom-atom interactions. In contrast, in our Letter, we use Hong-Ou-Mandel interference to postselect a spin-singlet state after overlapping two atoms in distinct spin states on an effective beam splitter. We verify the presence of entanglement and determine a bound on the postselected fidelity of a spin-singlet state of (0.62±0.03). The experiment has direct analogy to creating polarization entanglement with single photons and hence demonstrates the potential to use protocols developed for photons to create complex quantum states with noninteracting atoms.