A Feshbach engine in the Thomas-Fermi regime

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 with the fact that the efficiency of the engine is reduced by irreversible work if the strokes are done in a non-adiabatic 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.Comment: 8 pages, 7 figure

Fermionization of a Few-Body Bose System Immersed into a Bose-Einstein Condensate

We study the recently introduced self-pinning transition [Phys. Rev. Lett. 128, 053401 (2022)] in a quasi-one-dimensional two-component quantum gas in the case where the component immersed into the Bose-Einstein condensate has a finite intraspecies interaction strength. As a result of the matter-wave backaction, the fermionization in the limit of infinite intraspecies repulsion occurs via a first-order phase transition to the self-pinned state, which is in contrast to the asymptotic behavior in static trapping potentials. The system also exhibits an additional superfluid state for the immersed component if the interspecies interaction is able to overcome the intraspecies repulsion. We approximate the superfluid state in an analytical model and derive an expression for the phase transition line that coincides with well-known phase separation criteria in binary Bose systems. The full phase diagram of the system is mapped out numerically for the case of two and three atoms in the immersed component.Comment: 13 pages, 4 figure

Controlling Superfluid and Insulating States in Interacting Quantum Gases

In this thesis, I present two studies on controlling the state and properties of both single-species and composite quantum gases by tuning the various interaction strengths. In the first work, I derive a shortcut to adiabaticity (STA) for tuning a Feshbach resonance in repulsively interacting Bose-Einstein condensates (BECs) in the ThomasFermi regime. This shortcut mimics an adiabatic evolution and allows one to compress and expand a BEC without friction within an almost arbitrarily short time interval. I then use this technique to show how it can boost the performance of the so-called Feshbach quantum engine and also determine its limits and the instabilities it can lead to. The first part is complemented by a study demonstrating the general ineffectiveness of STAs as a tool to increase the attainable precision in critical quantum metrology at the example of two critical toy models. In the second part, I show that a strongly correlated one-dimensional quantum gas in the Tonks-Girardeau (TG) limit that is immersed into a BEC can undergo a transition to a crystal-like insulator state without any externally imposed lattice potential. I develop a model that accurately describes the system in the pinned insulator state, even if the TG gas has a finite temperature. Additionally, I study the superfluid state that can persist in the gas for finite interactions away from the TG limit and uncover the full phase diagram of the system.Okinawa Institute of Science and Technology Graduate Universit

Antagonistic Autoantibodies to Insulin-Like Growth Factor-1 Receptor Associate with Poor Physical Strength

Natural autoantibodies to the IGF1 receptor (IGF1R-aAb) have been described in relation to Graves' ophthalmopathy. Other physiological roles of natural IGF1R-aAb are not known. We hypothesized that IGF1R-aAb may be related to muscle development. Serum samples (n = 408) from young overweight subjects (n = 143) were collected during a lifestyle intervention study. Anthropometric parameters, along with leptin, IGF1 and IGF1R-aAb concentrations, were analyzed, and the subjects were categorized into positive or negative for IGF1R-aAb. Eleven out of 143 subjects (7.7%) were positive for IGF1R-aAb. Identified IGF1R-aAb were molecularly characterized and showed antagonistic activity in vitro impairing IGF1-mediated IGF1R activation. Mean body weight, height or age were similar between IGF1R-aAb-positive and -negative subjects, but IGF1 concentrations differed. Jumping ability, as well as right and left handgrip strengths, were lower in the IGF1R-aAb-positive as compared to the IGF1R-aAb-negative subjects. We conclude that natural IGF1R-aAb are detectable in apparently healthy subjects and are capable of antagonizing IGF1-dependent IGF1R activation. Moreover, the presence of IGF1R-aAb is associated with poor physical strength. Although the causality of this association is unclear, the data imply a potential influence of IGF1R autoimmunity on muscle development

Adiabatic critical quantum metrology cannot reach the Heisenberg limit even when shortcuts to adiabaticity are applied

We show that the quantum Fisher information attained in an adiabatic approach to critical quantum metrology cannot lead to the Heisenberg limit of precision and therefore regular quantum metrology under optimal settings is always superior. Furthermore, we argue that even though shortcuts to adiabaticity can arbitrarily decrease the time of preparing critical ground states, they cannot be used to achieve or overcome the Heisenberg limit for quantum parameter estimation in adiabatic critical quantum metrology. As case studies, we explore the application of counter-diabatic driving to the Landau-Zener model and the quantum Rabi model.Comment: 22 pages, 6 figure

The European Parliament and the UK’s renegotiation IV: what do MEPs think?

Debates about the future of UK-EU relations have paid little attention to the European Parliament. There have been no studies comparable to those that have looked into how member states view the renegotiation or might respond to a Brexit. Media reports indicate that the European Commission taskforce handling the UK renegotiation has even looked into ways of avoiding the Parliament becoming involved. Questions persist, however, as to whether the Parliament can be ignored. If Britain votes to leave then the EU Treaty’s withdrawal clause guarantees the Parliament a say in the final deal. To find out the views of the European Parliament BrexitVote is running a series – compiled by Tim Oliver – in which MEPs from across the Parliament set out what they think of the UK-EU renegotiation, the idea of Brexit and – most importantly – what role they think the Parliament will play. In this, the third part of the series, we hear from MEPs in the Confederal Group of the European United Left – Nordic Green Left and Greens/EFA groupings