22 research outputs found
Efficient Reduction of Casimir Forces by Self-assembled Bio-molecular Thin Films
Casimir forces, related to London-van der Waals forces, arise if the spectrum
of electromagnetic fluctuations is restricted by boundaries. There is great
interest both from fundamental science and technical applications to control
these forces on the nano scale. Scientifically, the Casimir effect being the
only known quantum vacuum effect manifesting between macroscopic objects,
allows to investigate the poorly known physics of the vacuum. In this work, we
experimentally investigate the influence of self-assembled molecular bio and
organic thin films on the Casimir force between a plate and a sphere. We find
that molecular thin films, despite being a mere few nanometers thick, reduce
the Casimir force by up to 14%. To identify the molecular characteristics
leading to this reduction, five different bio-molecular films with varying
chemical and physical properties were investigated. Spectroscopic data reveal a
broad absorption band whose presence can be attributed to the mixing of
electronic states of the underlying gold layer and those of the molecular film
due to charge rearrangement in the process of self-assembly. Using Lifshitz
theory we calculate that the observed change in the Casimir force is consistent
with the appearance of the new absorption band due to the formation of
molecular layers. The desired Casimir force reduction can be tuned by stacking
several monolayers, using a simple self-assembly technique in a solution. The
molecules - each a few nanometers long - can penetrate small cavities and
holes, and cover any surface with high efficiency. This process seems
compatible with current methods in the production of micro-electromechanical
systems (MEMS), which cannot be miniaturized beyond a certain size due to
`stiction' caused by the Casimir effect. Our approach could therefore readily
enable further miniaturization of these devices.Comment: Preprint versio
Laser ablation of energetic polymer solutions: effect of viscosity and fluence on the splashing behavior
Laser plasma thrusters are a new kind of propulsion system for small satellites, and work with the thrust created by the laser ablation of a target. Liquid polymer solutions are very promising fuels for such systems, provided that no splashing of the target occurs, because ejection of droplets strongly decreases the performances of the system. We have investigated the nanosecond infrared laser ablation of glycidyl azide polymer solutions containing carbon nanoparticles as absorber. Shadowgraphy imaging revealed two cases, namely splashing regime and solid-like behavior. The transition between both regimes depends on the viscosity of the solution and on the laser fluence, and is explained by the recoil force acting on the target. Appropriate conditions to avoid splashing were identified, showing that this liquid polymer solution is a suitable fuel for laser plasma thruster
Microscope objective for imaging atomic strontium with 0.63 micrometer resolution
Imaging and manipulating individual atoms with submicrometer separation can
be instrumental for quantum simulation of condensed matter Hamiltonians and
quantum computation with neutral atoms. Quantum gas microscope experiments in
most cases rely on quite costly solutions. Here we present an open-source
design of a microscope objective for atomic strontium consisting solely of
off-the-shelf lenses that is diffraction-limited for 461nm light. A
prototype built with a simple stacking design is measured to have a resolution
of 0.63(4)m, which is in agreement with the predicted value. This
performance, together with the near diffraction-limited performance for
532nm light makes this design useful for both quantum gas microscopes and
optical tweezer experiments with strontium. Our microscope can easily be
adapted to experiments with other atomic species such as erbium, ytterbium, and
dysprosium, as well as Rydberg experiments with rubidium
Solving correlation clustering with QAOA and a Rydberg qudit system: a full-stack approach
We study the correlation clustering problem using the quantum approximate
optimization algorithm (QAOA) and qudits, which constitute a natural platform
for such non-binary problems. Specifically, we consider a neutral atom quantum
computer and propose a full stack approach for correlation clustering,
including Hamiltonian formulation of the algorithm, analysis of its
performance, identification of a suitable level structure for
and specific gate design. We show the qudit implementation is superior to the
qubit encoding as quantified by the gate count. For single layer QAOA, we also
prove (conjecture) a lower bound of () for the approximation
ratio on 3-regular graphs. Our numerical studies evaluate the algorithm's
performance by considering complete and Erd\H{o}s-R\'enyi graphs of up to 7
vertices and clusters. We find that in all cases the QAOA surpasses the Swamy
bound for the approximation ratio for QAOA depths . Finally,
by analysing the effect of errors when solving complete graphs we find that
their inclusion severely limits the algorithm's performance.Comment: 22 + 11 page
Solving correlation clustering with QAOA and a Rydberg qudit system: a full-stack approach
We study the correlation clustering problem using the quantum approximate optimization algorithm (QAOA) and qudits, which constitute a natural platform for such non-binary problems. Specifically, we consider a neutral atom quantum computer and propose a full stack approach for correlation clustering, including Hamiltonian formulation of the algorithm, analysis of its performance, identification of a suitable level structure for 87Sr and specific gate design. We show the qudit implementation is superior to the qubit encoding as quantified by the gate count. For single layer QAOA, we also prove (conjecture) a lower bound of 0.6367 (0.6699) for the approximation ratio on 3-regular graphs. Our numerical studies evaluate the algorithm's performance by considering complete and Erdős-Rényi graphs of up to 7 vertices and clusters. We find that in all cases the QAOA surpasses the Swamy bound 0.7666 for the approximation ratio for QAOA depths p≥2. Finally, by analysing the effect of errors when solving complete graphs we find that their inclusion severely limits the algorithm's performance
Solving correlation clustering with QAOA and a Rydberg qudit system: a full-stack approach
We study the correlation clustering problem using the quantum approximate optimization algorithm (QAOA) and qudits, which constitute a natural platform for such non-binary problems. Specifically, we consider a neutral atom quantum computer and propose a full stack approach for correlation clustering, including Hamiltonian formulation of the algorithm, analysis of its performance, identification of a suitable level structure for 87Sr and specific gate design. We show the qudit implementation is superior to the qubit encoding as quantified by the gate count. For single layer QAOA, we also prove (conjecture) a lower bound of 0.6367 (0.6699) for the approximation ratio on 3-regular graphs. Our numerical studies evaluate the algorithm’s performance by considering complete and Erdős-Rényi graphs of up to 7 vertices and clusters. We find that in all cases the QAOA surpasses the Swamy bound 0.7666 for the approximation ratio for QAOA depths p ≥ 2. Finally, by analysing the effect of errors when solving complete graphs we find that their inclusion severely limits the algorithm’s performance
Prognostic factors associated with mortality risk and disease progression in 639 critically ill patients with COVID-19 in Europe: Initial report of the international RISC-19-ICU prospective observational cohort
Solving correlation clustering with QAOA and a Rydberg qudit system: a full-stack approach
We study the correlation clustering problem using the quantum approximate optimization algorithm (QAOA) and qudits, which constitute a natural platform for such non-binary problems. Specifically, we consider a neutral atom quantum computer and propose a full stack approach for correlation clustering, including Hamiltonian formulation of the algorithm, analysis of its performance, identification of a suitable level structure for 87Sr and specific gate design. We show the qudit implementation is superior to the qubit encoding as quantified by the gate count. For single layer QAOA, we also prove (conjecture) a lower bound of 0.6367 (0.6699) for the approximation ratio on 3-regular graphs. Our numerical studies evaluate the algorithm’s performance by considering complete and Erdős-Rényi graphs of up to 7 vertices and clusters. We find that in all cases the QAOA surpasses the Swamy bound 0.7666 for the approximation ratio for QAOA depths p ≥ 2. Finally, by analysing the effect of errors when solving complete graphs we find that their inclusion severely limits the algorithm’s performance
Solving correlation clustering with QAOA and a Rydberg qudit system: a full-stack approach
We study the correlation clustering problem using the quantum approximate optimization algorithm (QAOA) and qudits, which constitute a natural platform for such non-binary problems. Specifically, we consider a neutral atom quantum computer and propose a full stack approach for correlation clustering, including Hamiltonian formulation of the algorithm, analysis of its performance, identification of a suitable level structure for 87Sr and specific gate design. We show the qudit implementation is superior to the qubit encoding as quantified by the gate count. For single layer QAOA, we also prove (conjecture) a lower bound of 0.6367 (0.6699) for the approximation ratio on 3-regular graphs. Our numerical studies evaluate the algorithm's performance by considering complete and Erdős-Rényi graphs of up to 7 vertices and clusters. We find that in all cases the QAOA surpasses the Swamy bound 0.7666 for the approximation ratio for QAOA depths p≥2. Finally, by analysing the effect of errors when solving complete graphs we find that their inclusion severely limits the algorithm's performance