Superactivating Bound Entanglement in Quantum Networks via Quantum Zeno Dynamics and a Novel Algorithm for Optimized Zeno Evolution

Round 1

Reviewer 1 Report

Dear Authors, Your manuscript, “Superactivating Bound Entanglement in Quantum Networks via Quantum Zeno Dynamics” is interesting and, in my view, merits publication after revision. In section 1.1, you have a nice brief quantitative summary of supperactivation. Similar quantitative summary in 1.2 for quantum Zeno Dynamics should be provided. You often employ negative verbs and "not only... but also" clauses in your writing, which slows down the story and could be confusing. Here is my revision of some sentences of first paragraph of section 1.2 as an example: “Carefully designed frequent measurements can slow down the evolution 79 of a quantum system as well as drive it toward a target state. These processes are known as quantum Zeno effect (QZE) and quantum Zeno dynamics, respectively. …. Anti-Zeno effect has been recently attracting attentions to improve our understanding of the decay of quantum systems and its applications such as in quantum heat engines. … “

In the result section, it would be beneficial to present the states \rho in equations (11-15) pictorially, either with bar-plots or two dimensional coloured map.

Author Response

We thank Reviewer 1 very much for his/her precious time and efforts in reviewing our manuscript, and providing constructive comments. Please see the attached file for our responses on how we revised our manuscript accordingly.

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors re-evaluate the original protocol by Dur and Cirac which enables two distant nodes (not sharing any entanglement initially) out of five that can distill the Bell state when consecutive nodes share bipartite qubit bell states (randomly one of the four). The original protocol needs teleportations at three nodes and classical communication. The present work shows that this can be simplified with single qubit rotations and a threshold measurement by which a sufficient amount of bipartite and genuine multipartite entanglement can be distilled respectively among the last two nodes and throughout the network. 

The work seems exciting and can be considered for publication if the authors clarify the following confusions and elaborate on some of the studies:

1. How success probability scales with the number of iterations? Can you elaborate on this in both scenarios?

2. It would be interesting to know the structure of the states one ends up in scenario 2 after the last iteration. Is it always GHZ class?

3. It seems for a particular example in scenario 1, in each iteration the entanglement is flip-flopping between symmetric and antisymmetric subspace approximately. Does it stabilize after a certain number of iterations? If not, what this implies? Does the same happen in scenario 2?

4. Originality: I find that this work is an amalgamation of two original ideas that existed in literature. In fact, the network is exactly the same as Ref[13]. The new feature is the emergence of distillable GM. If you disagree, please tabularize differences. At least an application for GM in this network might add an interesting avenue.

Author Response

We thank Reviewer 2 very much for his/her precious time and efforts in reviewing our manuscript, and providing constructive comments. Please see the attached file for our responses on how we revised our manuscript accordingly.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have considered all of my questions and answered them adequately. The only criticism that I had about the originality of the research design, has not been appropriately addressed. I will clarify now why I feel the present research lacks sufficient originality.

1. Ref [13] has put forward the main idea for two qubits using teleportation and relay networks. This needs entangling gates.

2. It was improved by Ref[33] by some of the authors from the present work using Zeno dynamics (local measurements) in the same network considered in Ref[13].

3. This work develops on Ref [33] and extends it to multiparticle entanglements for qubits again in the same network considered in Ref[13]. The only useful finding of this study is that distillable entanglement can be found across all nodes.

4. Present work does not provide a new method and design or some elaborate extensions. The present calculation may pass for one of the studies that might lead to serious research.

The above discussions beg many questions about the novelty of the present work, such as,

1. Is this method universal across all networks? How to utilize this resource in certain protocols?

2. Is this method extendible to the higher dimensions?

3. Or, authors should be able to design some important improvements which will add sufficient novelty.

Without such improvement, the study does not qualify for publication.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf