Primordial Gravitational Wave Circuit Complexity

Round 1

Reviewer 1 Report

The manuscript investigates various physical implications of quantum circuit complexity of Primordial Gravitational Waves. The motivation is good, and the paper contains publishable results.

Author Response

Look at attached file for your reference.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors studied the quantum circuit complexity of PGW for various cosmological models, and for various initial states of PGW, by computing complexity measure and Von-Neumann entanglement entropy using both Covariance and Nielsen's wave function method. The results shows that quantum complexity could be a useful probe to study quantum features in cosmological scale. This is an interesting and timely topic, and the results are reasonable, which can be published, if the following minor comments can be addressed:

(1)   There are various typos in the current version;

(2)   The references are not enough. For instance, Page 10, for the reheating phase with $0<w<1/3$, the reference is absent. Actually, the EOS of universe during reheating phase is always quite different from this one. See for instance 1509.03524 and the references therein.

(3)   As mentioned in the article, the potential detection of PGW is through CMB. At least, the authors should briefly discuss or forecast the effect of quantum circuit complexity of PGW on CMB, which is much more interesting for the readers.

Author Response

Look at the attached file for your reference.

Author Response File: Author Response.pdf

Reviewer 3 Report

The article “PGW Circuit Complexity” investigates various physical implications of quantum circuit complexity using squeezed state formalism of Primordial Gravitational Waves. The paper is well written and proposes a novel idea in the interdisciplinary of quantum information and cosmology. Before publication I suggest the modification as below:

 

 

Major comments:

It would be nice to add a discussion to the paper in the direction the how quantum circuit complexity can be used as a probe to distinguish the early universe models (inflationary/bouncing) and Even in the paradigm of inflationary models, could it be used as a probe to distinguish models in the context? We should also note that the observables our CMB – temperature map, its polarization.

 

Minor comments:

1- I suggest using the whole word primordial gravitational wave instead of PGW in the title.

2- The references to the CMB observations and their relation to the inflationary models are not up-to-date use the articles below as an example:

https://arxiv.org/abs/1807.06211

https://arxiv.org/abs/1807.06209

 

3- There is no need to use capital letters for “Circuit Complexity”, “Entanglement”, “Quantum” and … please change them.

 

 

 

Author Response

Look at the attached files for your reference.

Author Response File: Author Response.pdf