Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Large-scale quantum systems with controllable interactions are important for understanding complex phenomena in nature, and are the basis for advanced quantum technologies. Realizing a controllable platform for controlling, understanding, and ultimately harnessing the entanglement is an outstanding challenge in quantum science. This project demonstrated reconfigurable arrays of individually-trapped ultracold atoms, thus realizing a platform that could demonstrate large-scale quantum entanglement with the addition of strong inter-atomic interactions. Arrays of more than 50 trap sites were formed via digital holography and a high- numerical aperture imaging system that featured in-situ trap diagnostics and single-atom imaging resolution. We further discovered a new implementation of a controlled-phase gate that utilized coherent excitation to Rydberg states. This method will enable robust entanglement protocols in many-atom systems such as the one developed here. ACKNOWLEDGEMENTS We would like to acknowledge support from the Sandia National Laboratories LDRD program.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We demonstrate a controlled phase gate approach to entangling neutral atoms using a tunable, Rydberg-dressed interaction. Previous approaches utilize a “dipole blockade” or a “spin-flip blockade” and thereby lack arbitrary phase control, and are less extensible to simultaneous entangling operations in many-atom systems. We systematically study major error mechanisms that limit the fidelity of the entangling interaction and find the dominant error mechanism to be phase noise in the coherent control of the single spins. Our work charts a definitive path to high fidelity entanglement using Rydberg-state-mediated interactions in neutral atoms.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We demonstrate matter-wave interference in a warm vapor of rubidium atoms. Established approaches to light-pulse atom interferometry rely on laser cooling to concentrate a large ensemble of atoms into a velocity class resonant with the atom optical light pulse. In our experiment, we show that clear interference signals may be obtained without laser cooling. This effect relies on the Doppler selectivity of the atom interferometer resonance. This interferometer may be configured to measure accelerations, and we demonstrate that multiple interferometers may be operated simultaneously by addressing multiple velocity classes.

We observe the nonlinearity of the Jaynes-Cummings (JC) ladder in the Autler-Townes spectroscopy of the hyperfine ground states for a Rydberg-dressed two-atom system. Here, the role of the two-level system in the JC model is played by the presence or absence of a collective Rydberg excitation, and the bosonic mode manifests as the number n of single-atom spin flips, symmetrically distributed between the atoms. We measure the normal-mode splitting and n nonlinearity as a function of detuning and Rabi frequency, thereby experimentally establishing the isomorphism with the JC model.

Abstract not provided.

Abstract not provided.

Our team has developed a new approach to entangling neutral atoms with a Rydberg-dressed interaction. Entangling neutral atoms is an essential key of quantum technologies such as quantum computation, many-body quantum simulation, and high-precision atomic sensors . The demonstrated Rydberg-dressed protocol involves adiabatically imposing a light shift on the ground state by coupling an excited Rydberg state with a tuned laser field. Using this technique, we have demonstrated a strong and tunable dipole - dipole interaction between two individually trapped atoms with energy shifts of order 1 MHz, which has been challenging to achieve in other protocols . During this program, we experimentally demonstrated Bell-state entanglement and the isomorphism to the Jaynes - Cumming model of a Rydberg-dressed two-atom system. Our theoretical calculations of a CPHASE quantum logic gate and arbitrary Dicke state quantum control in this system encourage further work.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Controlling the quantum entanglement between parts of a many-body system is key to unlocking the power of quantum technologies such as quantum computation, high-precision sensing, and the simulation of many-body physics. The spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform for such applications thanks to their long coherence times and the ability to control them with magneto-optical fields. However, the creation of strong coherent coupling between spins has been challenging. Here we demonstrate a strong and tunable Rydberg-dressed interaction between spins of individually trapped caesium atoms with energy shifts of order 1 MHz in units of Planck's constant. This interaction leads to a ground-state spin-flip blockade, whereby simultaneous hyperfine spin flips of two atoms are inhibited owing to their mutual interaction. We employ this spin-flip blockade to rapidly produce single-step Bell-state entanglement between two atoms with a fidelity 81(2)%.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We study a scheme for implementing a controlled-Z (cz) gate between two neutral-atom qubits based on the Rydberg blockade mechanism in a manner that is robust to errors caused by atomic motion. By employing adiabatic dressing of the ground electronic state, we can protect the gate from decoherence due to random phase errors that typically arise because of atomic thermal motion. In addition, the adiabatic protocol allows for a Doppler-free configuration that involves counterpropagating lasers in a σ+/σ- orthogonal polarization geometry that further reduces motional errors due to Doppler shifts. The residual motional error is dominated by dipole-dipole forces acting on doubly excited Rydberg atoms when the blockade is imperfect. For reasonable parameters, with qubits encoded into the clock states of Cs133, we predict that our protocol could produce a cz gate in <10 μs with error probability on the order of 10-3.

We study a scheme for implementing a controlled-Z (CZ) gate between two neutral-atom qubits based on the Rydberg blockade mechanism in a manner that is robust to errors caused by atomic motion. By employing adiabatic dressing of the ground electronic state, we can protect the gate from decoherence due to random phase errors that typically arise because of atomic thermal motion. In addition, the adiabatic protocol allows for a Doppler-free configuration that involves counterpropagating lasers in a σ₊/σ_- orthogonal polarization geometry that further reduces motional errors due to Doppler shifts. The residual motional error is dominated by dipole-dipole forces acting on doubly-excited Rydberg atoms when the blockade is imperfect. As a result, for reasonable parameters, with qubits encoded into the clock states of ¹³³Cs, we predict that our protocol could produce a CZ gate in < 10 μs with error probability on the order of 10^-3.

The interaction of Cs adatoms with mono- or bi-layered graphene (MLG and BLG), either free-standing or on a SiO2 substrate, was investigated using density functional theory. The most stable adsorption sites for Cs are found to be hollow sites on both graphene sheets and graphene-veiled SiO2(0001). Larger dipole moments are created when a MLG-veiled SiO2(0001) substrate is used for adsorption of Cs atoms compared to the adsorption on free-standing MLG, due to charge transfer occurring between the MLG and the SiO2 substrate. For the adsorption of Cs on BLG-veiled SiO2(0001) substrate, these differences are smoothed out and the binding energies corresponding to different sites are nearly degenerate; smaller dipole moments created by the Cs adatoms on BLG compared to MLG are also predicted.

Abstract not provided.

Abstract not provided.

We demonstrate a dual-axis accelerometer and gyroscope atom interferometer, which can form the building blocks of a six-axis inertial measurement unit. By recapturing the atoms after the interferometer sequence, we maintain a large atom number at high data rates of 50 to 100 measurements per second. Two cold ensembles are formed in trap zones located a few centimeters apart and are launched toward one another. During their ballistic trajectory, they are interrogated with a stimulated Raman sequence, detected, and recaptured in the opposing trap zone. We achieve sensitivities at μg/Hz and (μrad/s)/Hz levels, making this a compelling prospect for expanding the use of atom interferometer inertial sensors beyond benign laboratory environments.

We have theoretically and experimentally investigated the possibility of single atom deposition using laser cooled sources. In our theoretical work, we investigated an atom source composed of out-coupling from a Bose-Einstein condensate in a trap. A model was developed for Bose- Einstein-condensate-based devices. To illustrate its application, a 2-well system is studied. The results show interesting and possibly useful differences between operation with coherent (phased-locked) and incoherent (unlocked) population transfer between levels in the two wells. The two modes of operation are governed by an interplay among scattering, energy renormalizations and coupling between wells. In parallel, we have experimentally investigated the possibility of controlled deposition of single cesium atoms onto surfaces using optical tweezers. We have measured the rate limit for translation of single atoms in optical tweezers to be 45 mm/s for stepped translation, and have constructed an apparatus for deposition of single atoms on a sapphire substrate for future work.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We design and fabricate arrays of diffractive optical elements (DOEs) to realize neutral atom micro-traps for quantum computing. We initialize a single atom at each site of an array of optical tweezer traps for a customized spatial configuration. Each optical trapping volume is tailored to ensure only one or zero trapped atoms. Specifically designed DOEs can define an arbitrary optical trap array for initialization and improve collection efficiency in readout by introducing high-numerical aperture, low-profile optical elements into the vacuum environment. We will discuss design and fabrication details of ultra-fast collection DOEs integrated monolithically and coaxially with tailored DOEs that establish an optical array of micro-traps through far-field propagation. DOEs, as mode converters, modify the lateral field at the front focal plane of an optical assembly and transform it to the desired field pattern at the back focal plane of the optical assembly. We manipulate the light employing coherent or incoherent addition with judicious placement of phase and amplitude at the lens plane. This is realized through a series of patterning, etching, and depositing material on the lens substrate. The trap diameter, when this far-field propagation approach is employed, goes as 2.44λF/#, where the F/# is the focal length divided by the diameter of the lens aperture. The 8-level collection lens elements in this presentation are, to our knowledge, the fastest diffractive elements realized; ranging from F/1 down to F/0.025. © 2012 SPIE.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

A design concept, device layout, and monolithic microfabrication processing sequence have been developed for a dual-metal layer atom chip for next-generation positional control of ultracold ensembles of trapped atoms. Atom chips are intriguing systems for precision metrology and quantum information that use ultracold atoms on microfabricated chips. Using magnetic fields generated by current carrying wires, atoms are confined via the Zeeman effect and controllably positioned near optical resonators. Current state-of-the-art atom chips are single-layer or hybrid-integrated multilayer devices with limited flexibility and repeatability. An attractive feature of multi-level metallization is the ability to construct more complicated conductor patterns and thereby realize the complex magnetic potentials necessary for the more precise spatial and temporal control of atoms that is required. Here, we have designed a true, monolithically integrated, planarized, multi-metal-layer atom chip for demonstrating crossed-wire conductor patterns that trap and controllably transport atoms across the chip surface to targets of interest.

Abstract not provided.