3,973 research outputs found
Crossway Diffusion: Improving Diffusion-based Visuomotor Policy via Self-supervised Learning
Sequence modeling approaches have shown promising results in robot imitation
learning. Recently, diffusion models have been adopted for behavioral cloning,
benefiting from their exceptional capabilities in modeling complex data
distribution. In this work, we propose Crossway Diffusion, a method to enhance
diffusion-based visuomotor policy learning by using an extra self-supervised
learning (SSL) objective. The standard diffusion-based policy generates action
sequences from random noise conditioned on visual observations and other
low-dimensional states. We further extend this by introducing a new decoder
that reconstructs raw image pixels (and other state information) from the
intermediate representations of the reverse diffusion process, and train the
model jointly using the SSL loss. Our experiments demonstrate the effectiveness
of Crossway Diffusion in various simulated and real-world robot tasks,
confirming its advantages over the standard diffusion-based policy. We
demonstrate that such self-supervised reconstruction enables better
representation for policy learning, especially when the demonstrations have
different proficiencies.Comment: 18 pages, 10 figure
Bulk Rotational Symmetry Breaking in Kondo Insulator SmB6
Kondo insulator samarium hexaboride (SmB6) has been intensely studied in
recent years as a potential candidate of a strongly correlated topological
insulator. One of the most exciting phenomena observed in SmB6 is the clear
quantum oscillations appearing in magnetic torque at a low temperature despite
the insulating behavior in resistance. These quantum oscillations show multiple
frequencies and varied effective masses. The origin of quantum oscillation is,
however, still under debate with evidence of both two-dimensional Fermi
surfaces and three-dimensional Fermi surfaces. Here, we carry out
angle-resolved torque magnetometry measurements in a magnetic field up to 45 T
and a temperature range down to 40 mK. With the magnetic field rotated in the
(010) plane, the quantum oscillation frequency of the strongest oscillation
branch shows a four-fold rotational symmetry. However, in the angular
dependence of the amplitude of the same branch, this four-fold symmetry is
broken and, instead, a twofold symmetry shows up, which is consistent with the
prediction of a two-dimensional Lifshitz-Kosevich model. No deviation of
Lifshitz-Kosevich behavior is observed down to 40 mK. Our results suggest the
existence of multiple light-mass surface states in SmB6, with their mobility
significantly depending on the surface disorder level.Comment: 15 pages, 9 figure
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