1,223 research outputs found
Evaluation of liquid methane storage and transfer problems in supersonic aircraft
Evaluation of liquid methane storage and transfer problems for future supersonic aircraft cryogenic fuel requirement
Ytterbium nuclear-spin qubits in an optical tweezer array
We report on the realization of a fast, scalable, and high-fidelity qubit
architecture, based on Yb atoms in an optical tweezer array. We
demonstrate several attractive properties of this atom for its use as a
building block of a quantum information processing platform. Its nuclear spin
of 1/2 serves as a long-lived and coherent two-level system, while its rich,
alkaline-earth-like electronic structure allows for low-entropy preparation,
fast qubit control, and high-fidelity readout. We present a near-deterministic
loading protocol, which allows us to fill a 1010 tweezer array with
92.73(8)% efficiency and a single tweezer with 96.0(1.4)% efficiency. In the
future, this loading protocol will enable efficient and uniform loading of
target arrays with high probability, an essential step in quantum simulation
and information applications. Employing a robust optical approach, we perform
submicrosecond qubit rotations and characterize their fidelity through
randomized benchmarking, yielding 5.2(5) error per Clifford
gate. For quantum memory applications, we measure the coherence of our qubits
with =3.7(4) s and =7.9(4) s, many orders of magnitude longer than
our qubit rotation pulses. We measure spin depolarization times on the order of
tens of seconds and find that this can be increased to the 100 s scale through
the application of a several-gauss magnetic field. Finally, we use 3D
Raman-sideband cooling to bring the atoms near their motional ground state,
which will be central to future implementations of two-qubit gates that benefit
from low motional entropy.Comment: Fixed typos, refined scattering model, adds T1 dat
Mid-circuit operations using the omg-architecture in neutral atom arrays
We implement mid-circuit operations in a 48-site array of neutral atoms,
enabled by new methods for control of the
(optical-metastable-ground state qubit) architecture present in Yb.
We demonstrate laser-based control of ground, metastable and optical qubits
with average single-qubit fidelities of ,
and . With state-sensitive shelving between the ground and
metastable states, we realize a non-destructive state-detection for Yb,
and reinitialize in the ground state with either global control or local
feed-forward operations. We use local addressing of the optical clock
transition to perform mid-circuit operations, including measurement, spin
reset, and motional reset in the form of ground-state cooling. In
characterizing mid-circuit measurement on ground-state qubits, we observe raw
errors of on ancilla qubits and on data qubits, with
the former (latter) uncorrected for () preparation and
measurement error; we observe similar performance for mid-circuit reset
operations. The reported realization of the architecture and
mid-circuit operations are door-opening for many tasks in quantum information
science, including quantum error-correction, entanglement generation, and
metrology
Hyperpolarizability and operational magic wavelength in an optical lattice clock
Optical clocks benefit from tight atomic confinement enabling extended
interrogation times as well as Doppler- and recoil-free operation. However,
these benefits come at the cost of frequency shifts that, if not properly
controlled, may degrade clock accuracy. Numerous theoretical studies have
predicted optical lattice clock frequency shifts that scale nonlinearly with
trap depth. To experimentally observe and constrain these shifts in an
Yb optical lattice clock, we construct a lattice enhancement cavity
that exaggerates the light shifts. We observe an atomic temperature that is
proportional to the optical trap depth, fundamentally altering the scaling of
trap-induced light shifts and simplifying their parametrization. We identify an
"operational" magic wavelength where frequency shifts are insensitive to
changes in trap depth. These measurements and scaling analysis constitute an
essential systematic characterization for clock operation at the
level and beyond.Comment: 5 + 2 pages, 3 figures, added supplementa
First GIS analysis of modern stone tools used by wild chimpanzees (Pan troglodytes verus) in Bossou, Guinea, West Africa
Stone tool use by wild chimpanzees of West Africa offers a unique opportunity to explore the evolutionary roots of technology during human evolution. However, detailed analyses of chimpanzee stone artifacts are still lacking, thus precluding a comparison with the earliest archaeological record. This paper presents the first systematic study of stone tools used by wild chimpanzees to crack open nuts in Bossou (Guinea-Conakry), and applies pioneering analytical techniques to such artifacts. Automatic morphometric GIS classification enabled to create maps of use wear over the stone tools (anvils, hammers, and hammers/anvils), which were blind tested with GIS spatial analysis of damage patterns identified visually. Our analysis shows that chimpanzee stone tool use wear can be systematized and specific damage patterns discerned, allowing to discriminate between active and passive pounders in lithic assemblages. In summary, our results demonstrate the heuristic potential of combined suites of GIS techniques for the analysis of battered artifacts, and have enabled creating a referential framework of analysis in which wild chimpanzee battered tools can for the first time be directly compared to the early archaeological record.Leverhulme Trust [IN-052]; MEXT [20002001, 24000001]; JSPS-U04-PWS; FCT-Portugal [SFRH/BD/36169/2007]; Wenner-Gren Foundation for Anthropological Researc
Sub-recoil clock-transition laser cooling enabling shallow optical lattice clocks
Laser cooling is a key ingredient for quantum control of atomic systems in a
variety of settings. In divalent atoms, two-stage Doppler cooling is typically
used to bring atoms to the uK regime. Here, we implement a pulsed radial
cooling scheme using the ultranarrow 1S0-3P0 clock transition in ytterbium to
realize sub-recoil temperatures, down to tens of nK. Together with sideband
cooling along the one-dimensional lattice axis, we efficiently prepare atoms in
shallow lattices at an energy of 6 lattice recoils. Under these conditions key
limits on lattice clock accuracy and instability are reduced, opening the door
to dramatic improvements. Furthermore, tunneling shifts in the shallow lattice
do not compromise clock accuracy at the 10-19 level
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