1,031 research outputs found
All-Optical Formation of Quantum Degenerate Mixtures
We report the realization of quantum degenerate mixed gases of ytterbium (Yb)
isotopes using all-optical methods. We have succeeded in cooling attractively
interacting 176Yb atoms via sympathetic cooling down to below the Bose-Einstein
transition temperature, coexisting with a stable condensate of 174Yb atoms with
a repulsive interaction. We have observed a rapid atom loss in 176Yb atoms
after cooling down below the transition temperature, which indicates the
collapse of a 176Yb condensate. The sympathetic cooling technique has been
applied to cool a 173Yb-174Yb Fermi-Bose mixture to the quantum degenerate
regime.Comment: 4 pages, 3 figure
Degenerate Fermi Gases of Ytterbium
An evaporative cooling was performed to cool the fermionic 173Yb atoms in a
crossed optical dipole trap. The elastic collision rate, which is important for
the evaporation, turns out to be large enough from our study. This large
collision rate leads to efficient evaporation and we have successfully cooled
the atoms below 0.6 of the Fermi temperature, that is to say, to a quantum
degenerate regime. In this regime, a plunge of evaporation efficiency is
observed as the result of the Fermi degeneracy.Comment: 4 pages, 3figure
Bayesian Inference of Self-intention Attributed by Observer
Most of agents that learn policy for tasks with reinforcement learning (RL)
lack the ability to communicate with people, which makes human-agent
collaboration challenging. We believe that, in order for RL agents to
comprehend utterances from human colleagues, RL agents must infer the mental
states that people attribute to them because people sometimes infer an
interlocutor's mental states and communicate on the basis of this mental
inference. This paper proposes PublicSelf model, which is a model of a person
who infers how the person's own behavior appears to their colleagues. We
implemented the PublicSelf model for an RL agent in a simulated environment and
examined the inference of the model by comparing it with people's judgment. The
results showed that the agent's intention that people attributed to the agent's
movement was correctly inferred by the model in scenes where people could find
certain intentionality from the agent's behavior
Flat band induced non-Fermi liquid behavior of multicomponent fermions
We investigate multicomponent fermions in a flat band and predict
experimental signatures of non-Fermi liquid behavior. We use dynamical
mean-field theory to obtain the density, double occupancy and entropy in a Lieb
lattice for and components. We derive a
mean-field scaling relation between the results for different values of
, and study its breakdown due to beyond-mean field effects. The
predicted signatures occur at temperatures above the N\'eel temperature and
persist in presence of a harmonic trapping potential, thus they are observable
with current ultracold gas experiments.Comment: 6 pages, 5 figures and and a supplementary materia
Observation of the Mott Insulator to Superfluid Crossover of a Driven-Dissipative Bose-Hubbard System
Dissipation is ubiquitous in nature and plays a crucial role in quantum
systems such as causing decoherence of quantum states. Recently, much attention
has been paid to an intriguing possibility of dissipation as an efficient tool
for preparation and manipulation of quantum states. Here we report the
realization of successful demonstration of a novel role of dissipation in a
quantum phase transition using cold atoms. We realize an engineered dissipative
Bose-Hubbard system by introducing a controllable strength of two-body
inelastic collision via photo-association for ultracold bosons in a
three-dimensional optical lattice. In the dynamics subjected to a slow
ramp-down of the optical lattice, we find that strong on-site dissipation
favors the Mott insulating state: the melting of the Mott insulator is delayed
and the growth of the phase coherence is suppressed. The controllability of the
dissipation is highlighted by quenching the dissipation, providing a novel
method for investigating a quantum many-body state and its non-equilibrium
dynamics.Comment: 26 pages, 17 figure
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