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Adiabatic state distribution using anti-ferromagnetic spin systems

by Koen Groenland

Submission summary

As Contributors: Koen Groenland
Arxiv Link: https://arxiv.org/abs/1809.08158v2
Date submitted: 2018-12-06
Submitted by: Groenland, Koen
Submitted to: SciPost Physics
Domain(s): Theoretical
Subject area: Quantum Physics

Abstract

Transporting quantum information is an important prerequisite for quantum computers. We study how this can be done in Heisenberg-coupled spin networks using adiabatic control over the coupling strengths. We find that qudits can be transferred and entangled pairs can be created between distant sites of bipartite graphs with a certain balance between the maximum spin of both parts, extending previous results that were limited to linear chains. The transfer fidelity in a small star-shaped network is numerically analysed, and possible experimental implementations are discussed.

Current status:
Editor-in-charge assigned

Author comments upon resubmission

Many thanks to the referees for their careful reports and useful comments. I am happy to implement the requested changes, which I think enhance the clarity and readability of the paper. The individual points are commented on below.

Report 1:
1. Fig. 6 now has more clear annotations.

2. The energy level plots (e.g. Fig. 5) now show all energy levels of the system. I did the same for the other example that was analyzed (see below).

3. Regarding the short abstract: The SciPost author guidelines state that "The abstract should fit within 8 lines of the template.". If the editor permits slightly surpassing this limit, I would like to update the abstract as submitted, which I hope strikes a good balance between conciseness and fully covering of the contents of the paper.

Lastly, regarding the recommendation to numerically analyze more cases, including those which do work yet do not satisfy the requirements stated in the paper: Unfortunately I was unable to find precisely such cases. However, I appreciate the idea of giving a better intuition by addressing different systems and depicting what happens in cases beyond the scope of this work. I chose to include a case which does not work, yet is "very close to working", namely a case where the 'spin-s compatibility' is violated when the receiver disconnects (section 4.2).

Report 2:
1. I expanded the discussion of previous results in the field of state transfer over spin chains. A new subsection 1.1 was added to collect these results.

2. The last paragraph of Sec. 3.2 now discusses the connection between my entanglement distribution protocol, and the earlier result Ref. 7. Moreover, a reference to an earlier paper by the same authors, Campos Venuti et al. (2006) was also added.

I also appreciate the hint to include more concrete examples - I chose to numerically solve a case in which assumptions are violated, allowing a graphic presentation of how the transfer fails (section 4.2).

List of changes

- Added last line to abstract.
- Introduction: Re-arranged paragraphs such that first the protocol is explained, followed by the relation to existing literature. Added \subsections for the relation to previous work, and for the document structure. The literature discussion (now Sec. 1.1) was extended.
- 3rd paragraph of introduction: Added reference to Fig. 1 in the first line. Added lines at the end, which explain our contribution.
- Fig 4. caption is now more precise, mentioning explicitly that the ground state of V_{s,m} becomes degenerate.
- Fig 5. updated, now showing all energy levels.
- Fig 6. updated with better annotations.
- Sec. 3.2: Now explains the precise connection with the work of Campos Venuti at al. in the last paragraph.
- Sec 4.2: Added another numerical example, showing a case in which adiabatic transfer fails.
- Updated two citations that were recently published: Ban et al. (2018), Gratsea et al. (2018).


Invited Reports on this Submission

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Anonymous Report 1 on 2018-12-6

Strengths

1- Explanations are quite clear, including cartoon figures which really help with understanding
2- Nicely augments theory with numerical analysis
3- Thorough discussion of results, including what important issues could come up in the real world

Weaknesses

The main weaknesses of the paper have been addressed since the last report.

Report

I think the weaknesses I brought up before have been sufficiently addressed, it is understandable that the authors did not want to do too much more numerical work and I think there are still substantial results here. The additional numerics the authors did add have substantially improved the paper.

Requested changes

The authors have sufficiently addressed my comments and I now suggest publication without changes.

  • validity: high
  • significance: good
  • originality: ok
  • clarity: top
  • formatting: excellent
  • grammar: excellent

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