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Entangled states of dipolar bosons generated in a triplewell potential
by Arlei P. Tonel, Leandro H. Ymai, Karin Wittmann W., Angela Foerster, Jon Links
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Submission summary
Authors (as registered SciPost users):  Jon Links 
Submission information  

Preprint Link:  https://arxiv.org/abs/1909.04815v1 (pdf) 
Date submitted:  20190912 02:00 
Submitted by:  Links, Jon 
Submitted to:  SciPost Physics 
Ontological classification  

Academic field:  Physics 
Specialties: 

Approach:  Theoretical 
Abstract
We study the generation of entangled states using a device constructed from dipolar bosons confined to a triplewell potential. Dipolar bosons possess controllable, longrange interactions. This property permits specific choices to be made for the coupling parameters, such that the system is integrable. Integrability assists in the analysis of the system via an effective Hamiltonian constructed through a conserved operator. Through computations of fidelity we establish that this approach, to study the timeevolution of the entanglement for a class of nonentangled initial states, yields accurate approximations given by analytic formulae.
Current status:
Reports on this Submission
Anonymous Report 2 on 20191223 (Invited Report)
 Cite as: Anonymous, Report on arXiv:1909.04815v1, delivered 20191223, doi: 10.21468/SciPost.Report.1413
Strengths
The paper studies the behaviour of the system with respect to a variety of initial conditions for the integrable Hamiltonian and it provides a clear analysis of the entanglement generated under time evolution.
Weaknesses
1) No particular effort is done to motivate the study: it is written
that "the main goal is to expand on the analysis conducted in [18]", and
explore a variety of initial conditions plus a study of dynamics. Despite
it is understandable why this analysis may be desirable, the Authors do not elaborate enough on it in my opinion: what they expect from this study? why it is interesting? Since this analysis is restricted to states (4) where the number is defined, it is also clear that the analysis on these initial states is partial.
2) The Authors refer to their system as a "device": no effort is done to motivate the possible use in atomtronics, where, e.g., one would like to explore deviations from the integrable point. If from one side to call it "system" or "device" may be (to a certain extent) a matter of taste, at the same time it would be desirable to better motivate the use of the terminology "device", and may be to write "(e.g. see [20])" is not enough.
3) It would be important in my opinion to write the Hamiltonian of dipolar
bosons in a trimer configuration, and then discuss under what specific fine
tuning one gets the integrable Hamiltonian (1). If the Authors like to
emphasize that "Physical realisation of the system is feasible using dipolar atoms such as 52 Cr or 164 Dy" they should describe how and if this tuning is realistically possible.
4) It would be important to see (or at least to mention or discuss) the possible effect of periodic boundary conditions a^\dag_1 a_3.
Report
I consider the paper interesting and without flows, on a deserving subject,
but I see that several points may be improved according the previous list.
I then suggest the Authors consider the previous points.
Requested changes
According the previous list of improvable points:
1) I suggest to improve the motivational point of the paper, and discuss what other initial conditions could have been interesting to explore and why they
have been not considered (or perhaps left for future consideration?)
2) clarify the connection with atomtronics motivation  in that case please explain why the deviations from the integrable point may not spoil the analysis and the conclusions presented
3) present a derivation of (1) from the Hamiltonian of dipolar bosons in a threewell potential and discuss the fine tuning of parameters needed to obtain it
4) comment on the role of periodic boundary conditions
Anonymous Report 1 on 20191118 (Invited Report)
 Cite as: Anonymous, Report on arXiv:1909.04815v1, delivered 20191118, doi: 10.21468/SciPost.Report.1324
Report
In this paper the authors study the population and the entanglement dynamics for an integrable Hamiltonian describing a threewell Bose–Hubbard model obtained for a particular set of parameters. The time evolution sets in starting from nonentangled Fock states. What they predict is a coherent oscillation in the imbalance population between the first and the third well.
This result is verified comparing it with an analytic calculation obtained in the large interaction regime, the socalled resonant tunneling regime.
The paper is sound and well written, therefore I can recommend it for publication. However I would like the authors to clarify only few issues:
 In Fig. 8 the maximum value of the entropy is 1. Is it the plot of S/S_max instead of S? (is the entanglement entropy normalized by its maximum value?)
 Is there any reason why the time evolution of the entanglement entropy is lower for initial states with k=0, namely when the third well is empty at the initial time?
 I would expect that the fidelity, defined as the overlap between the exact state and the one obtained by the coherent state approximation, approaches value 1 upon increasing U, namely going deeply in the coherent tunneling regime, while Fig. 9 does not show such expected behavior. Fig. 9 shows, instead, that the fidelity seems sensitive to the initial polulation of the second well. Could the authors comment on that?