Quantum Reports

Special Issue Editor

Special Issue Information

Dear Colleagues,

We are pleased to announce the new Special Issue “Exclusive Feature Papers of Quantum Reports in 2024–2025”, a collection of significant high-quality papers (original research articles or comprehensive review papers) published in an open access format by editorial board members or leading scholars invited by the editorial board and guest editors. This Special Issue aims to discuss emerging knowledge and new developments on the frontiers in the field of quantum science research via the publication of selected works that will, hopefully, greatly contribute to society. We hope that this Special Issue will serve as the best forum for disseminating outstanding research results and sharing innovative ideas in the field.

Prof. Dr. Lajos Diósi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Quantum Reports is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Related Special Issue

Published Papers (2 papers)

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Research

31 pages, 2408 KiB

Open AccessFeature PaperArticle

A Dyson Brownian Motion Model for Weak Measurements in Chaotic Quantum Systems

by Federico Gerbino, Pierre Le Doussal, Guido Giachetti and Andrea De Luca

Quantum Rep. 2024, 6(2), 200-230; https://0-doi-org.brum.beds.ac.uk/10.3390/quantum6020016 - 16 May 2024

Viewed by 217

Abstract

We consider a toy model for the study of monitored dynamics in many-body quantum systems. We study the stochastic Schrödinger equation resulting from continuous monitoring with a rate

Γ

of a random Hermitian operator, drawn from the Gaussian unitary ensemble (GUE) at every [...] Read more.

We consider a toy model for the study of monitored dynamics in many-body quantum systems. We study the stochastic Schrödinger equation resulting from continuous monitoring with a rate

Γ

of a random Hermitian operator, drawn from the Gaussian unitary ensemble (GUE) at every time t. Due to invariance by unitary transformations, the dynamics of the eigenvalues

{λ_{α}}_{α = 1}^{n}

of the density matrix decouples from that of the eigenvectors, and is exactly described by stochastic equations that we derive. We consider two regimes: in the presence of an extra dephasing term, which can be generated by imperfect quantum measurements, the density matrix has a stationary distribution, and we show that in the limit of large size

n \to \infty

it matches with the inverse-Marchenko–Pastur distribution. In the case of perfect measurements, instead, purification eventually occurs and we focus on finite-time dynamics. In this case, remarkably, we find an exact solution for the joint probability distribution of

λ

’s at each time t and for each size n. Two relevant regimes emerge: at short times

t Γ = O (1)

, the spectrum is in a Coulomb gas regime, with a well-defined continuous spectral distribution in the

n \to \infty

limit. In that case, all moments of the density matrix become self-averaging and it is possible to exactly characterize the entanglement spectrum. In the limit of large times

t Γ = O (n)

, one enters instead a regime in which the eigenvalues are exponentially separated

\log (λ_{α} / λ_{β}) = O (Γ t / n)

, but fluctuations

\sim O (\sqrt{Γ t / n})

play an essential role. We are still able to characterize the asymptotic behaviors of the entanglement entropy in this regime. Full article

(This article belongs to the Special Issue Exclusive Feature Papers of Quantum Reports in 2024–2025)

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Figure 1

12 pages, 4665 KiB

Open AccessFeature PaperArticle

Spectral Analysis of Proton Eigenfunctions in Crystalline Environments

by Luca Gamberale and Giovanni Modanese

Quantum Rep. 2024, 6(2), 172-183; https://0-doi-org.brum.beds.ac.uk/10.3390/quantum6020014 - 6 May 2024

Viewed by 277

Abstract

The Schrödinger equation and Bloch theorem are applied to examine a system of protons confined within a periodic potential, accounting for deviations from ideal harmonic behavior due to real-world conditions like truncated and non-quadratic potentials, in both one-dimensional and three-dimensional scenarios. Numerical computation [...] Read more.

N_{w}

, reminiscent of a finite harmonic oscillator spectrum. In contrast to electronic energy bands, the proton system displays a greater number of possible bound states due to the significant mass of protons. Extending previous research, this study rigorously determines the constraints on the energy gap and oscillation amplitude of the previously identified coherent states. The deviations in energy level spacing identified in the computed spectrum, leading to the minor splitting of electromagnetic modes, are analyzed and found not to hinder the onset of coherence. Finally, a more precise value of the energy gap is determined for the proton coherent states, ensuring their stability against thermal decoherence up to the melting temperature of the hosting metal. Full article

(This article belongs to the Special Issue Exclusive Feature Papers of Quantum Reports in 2024–2025)

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