97 research outputs found
Simulating seeded vacuum decay in a cold atom system
We propose to test the concept of seeded vacuum decay in cosmology using an
analogue gravity Bose-Einstein condensate system. The role of the nucleation
seed is played by a vortex within the condensate. We present two complementary
theoretical analyses that demonstrate seeded decay is the dominant decay
mechanism of the false vacuum. First, we adapt the standard instanton methods
to the Gross-Pitaevskii equation. Second, we use the truncated Wigner method to
study vacuum decay.Comment: 5 Pages, 4 figures, new intro in v
Mean-field analog of the Hong-Ou-Mandel experiment with bright solitons
In the present work, we theoretically propose and numerically illustrate a mean-field analog of the Hong-Ou-Mandel experiment with bright solitons.More specifically, we scatter two solitons off of each other (in our setup,the bright solitons play the role of a classical analog to the quantum photons of the original experiment), while the role of the beam splitter is played by a repulsive Gaussian barrier. In our classical scenario, distinguishability of the particles yields, as expected, a 0.5 split mass on either side. Nevertheless, for very slight deviations from the completely symmetric scenario, a near-perfect transmission can be constructed instead, very similarly to the quantum-mechanical output. We demonstrate this as a generic feature under slight variations of the relative soliton speed, or of the relative amplitude in a wide parametric regime. We also explore how variations of the properties of the “beam splitter” (i.e., the Gaussian barrier) affect this phenomenology
Quantum Droplets in Imbalanced Atomic Mixtures
Quantum droplets are a quantum analogue to classical fluid droplets in that
they are self-bound and display liquid-like properties -- such as
incompressibility and surface tension -- though their stability is the result
of quantum fluctuations. One of the major systems for observing quantum
droplets is two-component Bose gases. Two-component droplets are typically
considered to be balanced, having a fixed ratio between the densities of the
two component. This work goes beyond the fixed density ratio by investigating
spherical droplets in imbalanced mixtures. With increasing imbalance, the
droplet is able to lower its energy up to a limit, at which point the droplet
becomes saturated with the atoms of the majority component and any further
atoms added to this component cannot bind to the droplet. Analysing the
breathing mode dynamics of imbalanced droplets indicates that the droplet can
emit particles, as in balanced mixtures, but the imbalance leads to an
intricate superposition of multiple simultaneously decaying collective
oscillations.Comment: 13 pages, 5 figure
Trapped Imbalanced Quantum Droplets
A two-component quantum droplet is an attractive mixture of ultracold bosons
stabilised against collapse by quantum fluctuations. Commonly, two-component
quantum droplets are studied within a balanced mixture. However, the mixture
can be imbalanced resulting in a lower energy but less stably bound droplet, or
even a droplet submerged in a gas. This work focuses on the experimentally
relevant question: how are imbalanced droplets modified by harmonic trap
potentials? Droplet ground states and breathing modes are analysed across the
two-dimensional parameter space of imbalance and trap strength. The robustness
of the droplet imbalance is also studied by releasing the droplet from the
trap, demonstrating that this can lead to the creation of free-space,
imbalanced droplets.Comment: 11 pages, 4 figure
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