Feshbach engine in the Thomas-Fermi regime

Abstract

Bose-Einstein condensates can be used to produce work by tuning the strength of the interparticle interactions with the help of Feshbach resonances. In inhomogeneous potentials, these interaction ramps change the volume of the trapped gas, allowing one to create a thermodynamic cycle known as the Feshbach engine. However, in order to obtain a large power output, the engine strokes must be performed on a short timescale, which is in contrast to the fact that the efficiency of the engine is reduced by irreversible work if the strokes are done in a nonadiabatic fashion. Here we investigate how such an engine can be run in the Thomas-Fermi regime and present a shortcut to adiabaticity that minimizes the irreversible work and allows for efficient engine operation.

Time-optimal variational control of bright matter-wave soliton

“…In summary, we have studied the variation control of bright soliton matter-wave by manipulating the atomic attraction through Feshbach resonances. By using the variational approximation the motion equation is derived for capturing the soliton's shape, without dynamical invariant [33] or Thomas-Fermi limit [32,39,40]. Sharing with the concept of STA, we engineer inversely the atom-atom interaction for achieving the fast but stable soliton decompression within shorter time.…”

“…More specifically, since the time-dependent variational principle can find a set of Newton-like ordinary differential equations for the parameters (i.e. the width of cloud, center and interatomic interaction), the variational control provides a promising alternative, aiming at accelerating the adiabatic compression/decompression of BECs and bright solitons [28,31], beyond the harmonic approximation of the potential [30] and Thomas-Fermi limit [32,39,40]. In this scenario, the Lewis-Riesenfeld dynamical invariant and general scaling transformations [32,33] are not required in the context of inverse engineering.…”

Quantum thermodynamic devices: from theoretical proposals to experimental reality

“…This theoretical proposal opens the door to a variety of potential devices that operate with a BEC as a working medium. For instance, Keller et al 332 analyzed only recently how work can be extracted from the Feshbach resonances.…”

“…As particles in the zero-momentum state cannot exert pressure, it is not easy to see how the typical paradigm for work extraction from thermal machines, involving pressure exerted against an external piston or potential, translates to a BEC working medium. This has led to inventive proposals for BEC-based engines, including extracting work by manipulating the interparticle interaction strength using Feshbach resonances 175,332 and using BECs as the basis for thermal machines that act on a working medium of quantum fields 333 .…”

Time-optimal variational control of a bright matter-wave soliton

“…By now, the variational technique, originally proposed in a nonlinear problem [27,28], has been developed for STA in particular systems [29][30][31][32] that cannot be treated by means of other existing approaches, i.e., invariant-based engineering [33,34], counterdiabatic driving [35][36][37], and fast-forward scaling [38,39]. More specifically, since the time-dependent variational principle can find a set of Newton-like ordinary differential equations for the parameters (i.e., the width of cloud, center, and interatomic interaction), the variational control provides a promising alternative aimed at accelerating the adiabatic compression or decompression of BECs and bright solitons [29,32], beyond the harmonic approximation of the potential [31] and Thomas-Fermi limit [33,40,41]. In this scenario, the Lewis-Riesenfeld dynamical invariant and general scaling transformations [33,34] are not required in the context of inverse engineering.…”