No Arabic abstract
One of the most important task in physics today is to merge quantum mechanics and general relativity into one framework. And the main barrier in this task is that we lack quantum gravitational phenomena in experiments. An important way to get quantum gravitational phenomena is to study quantum effects in a macro-scale system in which gravity will play a role. In this article, we want to study dynamics of a possible macro-scale system: liquid helium droplets with radius of 100nm under low temperature and low pressure. Our idea is to observe the interference phenomenon of this system and find the similarities and difference between it and quantum system. We gave a practical experiment design to observe the interference, including a possible method to realize an approximate square barrier. We also gave an illustration on what a quantum or a classical interferogram of our system looks like theoretically.
The quantized lateral motional states and the spin states of electrons trapped on the surface of superfluid helium have been proposed as basic building blocks of a scalable quantum computer. Circuit quantum electrodynamics (cQED) allows strong dipole coupling between electrons and a high-Q superconducting microwave resonator, enabling such sensitive detection and manipulation of electron degrees of freedom. Here we present the first realization of a hybrid circuit in which a large number of electrons are trapped on the surface of superfluid helium inside a coplanar waveguide resonator. The high finesse of the resonator allows us to observe large dispersive shifts that are many times the linewidth and make fast and sensitive measurements on the collective vibrational modes of the electron ensemble, as well as the superfluid helium film underneath. Furthermore, a large ensemble coupling is observed in the dispersive regime during experiment, and it shows excellent agreement with our numeric model. The coupling strength of the ensemble to the cavity is found to be >1 MHz per electron, indicating the feasibility of achieving single electron strong coupling.
We demonstrate spontaneous bidirectional motion of droplets on liquid infused surfaces in the presence of a topographical gradient, in which the droplets can move either toward the denser or the sparser solid fraction area. Our analytical theory explains the origin of this bidirectional motion. Furthermore, using both lattice Boltzmann simulations and experiments, we show that the key factor determining the direction of motion is the wettability difference of the droplet on the solid surface and on the lubricant film. The bidirectional motion is shown for various combinations of droplets and lubricants, as well as for different forms of topographical gradients.
We investigate the structure of the [bmim][Tf2N]/silica interface by simulating the indentation of a thin (4 nm) [bmim][Tf2N] film by a hard nanometric tip. The ionic liquid/silica interface is represented in atomistic detail, while the tip is modelled by a spherical mesoscopic particle interacting via an effective short-range potential. Plots of the normal force (Fz) on the tip as a function of its distance from the silica surface highlight the effect of weak layering in the ionic liquid structure, as well as the progressive loss of fluidity in approaching the silica surface. The simulation results for Fz are in near-quantitative agreement with new AFM data measured on the same [bmim][Tf2N]/silica interface at comparable thermodynamic conditions.
Archimedes is a feasibility study of a future experiment to ascertain the interaction of vacuum fluctuations with gravity. The experiment should measure the force that the earths gravitational field exerts on a Casimir cavity by using a small force detector. Here we analyse the main parameters of the experiment and we present its conceptual scheme, which overcomes in principle the most critical problems.
The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction and short-range repulsion. Magnetic quantum gases and in particular Dysprosium gases, offering a comparable short-range contact and a long-range dipolar interaction energy, remarkably exhibit such emergent phenomena. In addition an effective cancellation of mean-field effects of the two interactions results in a pronounced importance of quantum-mechanical beyond mean-field effects. For a weakly-dominant dipolar interaction the striking consequence is the existence of a new state of matter equilibrated by the balance between weak mean-field attraction and beyond mean-field repulsion. Though exemplified here in the case of dipolar Bose gases, this state of matter should appear also with other microscopic interactions types, provided a competition results in an effective cancellation of the total mean-field. The macroscopic state takes the form of so-called quantum droplets. We present the effects of a long-range dipolar interaction between these droplets.