Quantum Turbulence in Quantum Gases

García-Orozco

Santos

et al. 2020

Entropy

Quantum turbulence deals with the phenomenon of turbulence in quantum fluids, such as superfluid helium and trapped Bose-Einstein condensates (BECs). Although much progress has been made in understanding quantum turbulence, several fundamental questions remain to be answered. In this work, we investigated the entropy of a trapped BEC in several regimes, including equilibrium, small excitations, the onset of turbulence, and a turbulent state. We considered the time evolution when the system is perturbed and let to evolve after the external excitation is turned off. We derived an expression for the entropy consistent with the accessible experimental data, which is, using the assumption that the momentum distribution is well-known. We related the excitation amplitude to different stages of the perturbed system, and we found distinct features of the entropy in each of them. In particular, we observed a sudden increase in the entropy following the establishment of a particle cascade. We argue that entropy and related quantities can be used to investigate and characterize quantum turbulence.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Entropy of a Turbulent Bose-Einstein Condensate

García-Orozco

Santos

et al. 2020

Entropy

“…The initial phase of the experiment consists in the production of a Bose-Einstein condensate, containing approximately 4 × 10 5 87 Rb atoms in the hyperfine state |F, m F = |2, 2 , confined in a Quadrupole-Ioffe configuration (QUIC) magnetic trap of frequencies ω r /2π = 237.3(8) Hz and ω x /2π = 18.7(2) Hz. The unperturbed BEC has a condensate fraction of 70(5)%, chemical potential µ 0 /k B = 124(5) nK, and healing length ξ 0 = 0.15 (2) µm. Details of the experimental procedure and other technical remarks can be found in previous works [4,20,21].…”

Section: Methodsmentioning

confidence: 99%

“…The route to equilibration of a many-body quantum system driven to a far-from-equilibrium state is a question that permeates several areas in physics. Quantum turbulence [1,2] is an example of such out-of-equilibrium systems. Its classical counterpart, classical turbulence, is a process that occurs in many types of fluids, spanning the climatic effects involving large masses down to capillaries.…”

Section: Introductionmentioning

confidence: 99%

Entropy of a Turbulent Bose-Einstein Condensate

García-Orozco

Santos

et al. 2020

Preprint

Quantum turbulence deals with the phenomenon of turbulence in quantum fluids, such as superfluid helium and trapped Bose-Einstein condensates (BECs). Although much progress has been made in understanding quantum turbulence, several fundamental questions remain to be answered. In this work, we investigated the entropy of a trapped BEC in several regimes, including equilibrium, small excitations, the onset of turbulence, and a turbulent state. We considered the time evolution when the system is perturbed and let to evolve after the external excitation is turned off. We derived an expression for the entropy consistent with the accessible experimental data, that is, using the assumption that the momentum distribution is well-known. We related the excitation amplitude to different stages of the perturbed system, and we found distinct features of the entropy in each of them. In particular, we observed a sudden increase in the entropy following the establishment of a particle cascade. We argue that entropy and related quantities can be used to investigate and characterize quantum turbulence.

“…An unperturbed condensate is a superfluid. With the introduction of excitations, which can generate vortices and waves in this superfluid, quantum turbulence can be reached [14,15]. Once in this state, we have many amplitude and phase fluctuations, reaching a situation very similar to that expected in speckle fields.…”

Section: Free Expansion Of a Turbulent Quantum Cloud Of Cold Atoms: Tmentioning

confidence: 97%

Cold Atoms Beyond Atomic Physics

Bagnato

2020

Braz J Phys

In the last 25 years, much progress has been made producing and controlling Bose-Einstein condensates (BECs) and degenerate Fermi gases. The advances in trapping, cooling, and tuning the interparticle interactions in these cold atom systems lead to an unprecedented amount of control that one can exert over them. This work aims to show that knowledge acquired studying cold atom systems can be applied to other fields that share similarities and analogies with them, provided that the differences are also known and taken into account. We focus on two specific fields: nuclear physics and statistical optics. The nuclear physics discussion occurs with the BCS-BEC crossover in mind, in which we compare cold Fermi gases with nuclear and neutron matter and nuclei. We connect BECs and atom lasers through both systems' matter-wave character for the analogy with statistical optics. Finally, we present some challenges that, if solved, would increase our understanding of cold atom systems and, thus, the related areas.