麻豆淫院

Bloch oscillations are periodic oscillations of quantum particles in a repeating energy "landscape" (e.g., a crystal lattice) that are subjected to a constant force. These particle motions have been the focus of numerous physics studies, as they are intriguing quantum effects that are not predicted by classical mechanics theories.

Probing Bloch oscillations experimentally could thus yield new insight into the fundamental properties of quantum matter. So far, they have been primarily studied in individual particles or two-particle systems, as opposed to quantum many-body systems comprised of several particles.

Researchers at CNRS- ENS-PSL University and Sorbonne University report the observation of collective Bloch oscillations in a one-dimensional (1D) Bose gas, a quantum fluid comprised of bosons, which are particles that can occupy the same quantum state.

Their paper, , demonstrates that these widely studied types of particle movements can also be observed for composite systems while also opening new possibilities for the study of many-body interactions.

"The motivation for realizing this experiment came from a discussion with a colleague, N. Pavloff, who told about a recent theory work he performed in collaboration with the team of A. Recati in Trento, Italy," Jerome Beugnon, senior author of the paper, told 麻豆淫院.

"I was attracted by the project for two reasons. The predicted behavior is spectacular and very counterintuitive: if you exert a constant and uniform force on the studied wavepacket of atoms, this wavepacket will oscillate in space.

"Whereas this is well-known (as Bloch oscillations) in quantum mechanics, when a single particle is evolving in a lattice potential (like electrons in solids), this is much more surprising for a system without a lattice. It is the quantum nature of the bath in which the wavepacket is moving that is the key to explaining this behavior."

While theoretical physicists have provided a good understanding of many-body Bloch oscillations, testing their theories experimentally has often proved challenging. In their paper, Beugnon and his colleagues introduce a new experimental platform that enables the realization of collective Bloch oscillations and could thus help to test these theories.

"The physical system we employed is a mixture of two components of ultracold atoms," explained Beugnon. "We create a wave packet of one of the components and study its motion in a bath made of the other component. The atoms are trapped by laser potentials, and the external force we apply on the system is a magnetic force."

In the physical system they realized, the researchers were able to observe Bloch oscillations involving approximately 1,000 particles, which had never been achieved before. This is a remarkable achievement, considering that the oscillations reported in most earlier works were not collective, but were instead limited to one or two particles.

"Our observation is a great example to reveal the specific properties of one-dimensional quantum systems, here the periodicity of their dispersion relation," said Beugnon.

"We have also extended the theory study to the case of atoms moving in a ring geometry and show the interplay between Bloch oscillations and the creation of quantized superfluid currents during the motion."

The recent work by Beugnon and his colleagues introduces a new promising experimental platform to study collective motions in strongly interacting quantum systems. Future research probing the physical system that they examined, or other similar systems, could improve the present understanding of many-body interactions, while also allowing physicists to test some unconfirmed theoretical predictions.

"The wavepacket we have studied is a so-called magnetic soliton," added Beugnon. "In practice, this is one example of a larger family of magnetic solitons. The dynamics of more general magnetic solitons is expected to be very rich, and we plan to explore them in the future."

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