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Universe
Special Issues
Quantum Dynamics and Applications
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Quantum Dynamics and Applications

A special issue of Universe (ISSN 2218-1997).

Deadline for manuscript submissions: closed (15 October 2019) | Viewed by 16133

Special Issue Editors

Prof. Dr. Shumpei Masuda

E-Mail Website
Guest Editor
College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Ichikawa, Chiba 272-0827, Japan
Interests: quantum control; quantum optics; quantum dynamics
Dr. Kuan Yen Tan

E-Mail Website
Guest Editor
Department of Applied Physics, Aalto University, Espoo, Finland
Interests: low-temperature physics; microwave photonics; quantum computing
Prof. Dr. Mikio Nakahara

E-Mail Website
Guest Editor
Department of Mathematics, Shanghai University, Shanghai 200444, China
Interests: quantum control; quantum information; quantum computing

Special Issue Information

Dear Colleagues,

Quantum technologies are a rapidly emerging field. Many countries and large corporations are ramping up their investment in quantum technology, particularly in quantum information processing. However, these systems require extremely fast and precise controls because, over time, quantum systems lose their “coherence”, which refers to the ability to make interference and superposition of states. Maintaining this “coherence” is at the heart of all the mechanisms utilized in quantum technology. Therefore, the key to the further advancement of quantum technology relies on fast and accurate quantum control protocols. However, finding an optimum temporal and spatial dependence of the control field for high-speed manipulations is extremely challenging because fast controls require a strong control field, which can easily cause undesirable perturbation to the system, thus, negating its useful superposition.

This Special Issue of Universe is devoted to recent developments in the methodology of fast, efficient, and accurate controls of quantum systems and their applications. This Special Issue not only focuses on practical purposes, but also aims to deepen the understanding of the world from the perspective of high-fidelity quantum control.

Topics of interest for this Special Issue include, but are not limited to:

  • Methodology and applications of fast and accurate quantum controls.
  • Improvements of the efficiency of qubit gate operations, chemical reactions, and the engineering of electromagnetic environments of solid-state quantum systems.
  • Dynamical properties of controllable quantum systems.

Prof. Dr. Shumpei Masuda
Dr. Kuan Yen Tan
Prof. Dr. Mikio Nakahara
Guest Editors

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. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. 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.

Keywords

  • Fast and accurate quantum control
  • Quantum dynamics
  • Quantum technology

Published Papers (5 papers)

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Research

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8 pages, 2535 KiB  
Article
Comparison of Strain Effect between Aluminum and Palladium Gated MOS Quantum Dot Systems
by Brian Chi Ho Mooy, Kuan Yen Tan and Nai Shyan Lai
Universe 2020, 6(4), 51; https://doi.org/10.3390/universe6040051 - 6 Apr 2020
Cited by 1 | Viewed by 2507
Abstract
As nano-scale metal-oxide-semiconductor devices are cooled to temperatures below 1 K, detrimental effects due to unintentional dots become apparent. The reproducibility of the location of these unintentional dots suggests that there are other mechanisms in play, such as mechanical strains in the semiconductor [...] Read more.
As nano-scale metal-oxide-semiconductor devices are cooled to temperatures below 1 K, detrimental effects due to unintentional dots become apparent. The reproducibility of the location of these unintentional dots suggests that there are other mechanisms in play, such as mechanical strains in the semiconductor introduced by metallic gates. Here, we investigate the formation of strain-induced dots on aluminum and palladium gated metal oxide semiconductor (MOS) quantum devices using COMSOL Multiphysics. Simulation results show that the strain effect on the electrochemical potential of the system can be minimized by replacing aluminum with palladium as the gate material and increasing the thickness of the gate oxide. Full article
(This article belongs to the Special Issue Quantum Dynamics and Applications)
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18 pages, 1043 KiB  
Article
Theoretical Study on Spin-Selective Coherent Electron Transfer in a Quantum Dot Array
by Shumpei Masuda, Kuan Yen Tan and Mikio Nakahara
Universe 2020, 6(1), 2; https://doi.org/10.3390/universe6010002 - 22 Dec 2019
Cited by 2 | Viewed by 2638
Abstract
Recently, we proposed the spin-selective coherent electron transfer in a silicon-quantum-dot array. It requires temporal tuning of two pulses of an oscillating magnetic field and gate voltage control. This paper proposes a simpler method that requires a single pulse of oscillating magnetic field [...] Read more.
Recently, we proposed the spin-selective coherent electron transfer in a silicon-quantum-dot array. It requires temporal tuning of two pulses of an oscillating magnetic field and gate voltage control. This paper proposes a simpler method that requires a single pulse of oscillating magnetic field and gate voltage control. We examined the robustness of the control against the error in the pulse amplitude and the effect of the excited states relaxation to the control efficiency. In addition, we propose a novel control method based on a shortcuts-to-adiabaticity protocol, which utilizes two pulses but requires temporal control of the pulse amplitude for only one of them. We compared their efficiencies under the effect of realistic pulse amplitude errors and relaxation. Full article
(This article belongs to the Special Issue Quantum Dynamics and Applications)
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17 pages, 11634 KiB  
Article
Driving Interactions Efficiently in a Composite Few-Body System
by Alan Kahan, Thomás Fogarty, Jing Li and Thomas Busch
Universe 2019, 5(10), 207; https://doi.org/10.3390/universe5100207 - 7 Oct 2019
Cited by 5 | Viewed by 2992
Abstract
We study how to efficiently control an interacting few-body system consisting of three harmonically trapped bosons. Specifically, we investigate the process of modulating the inter-particle interactions to drive an initially non-interacting state to a strongly interacting one, which is an eigenstate of a [...] Read more.
We study how to efficiently control an interacting few-body system consisting of three harmonically trapped bosons. Specifically, we investigate the process of modulating the inter-particle interactions to drive an initially non-interacting state to a strongly interacting one, which is an eigenstate of a chosen Hamiltonian. We also show that for unbalanced subsystems, where one can individually control the different inter- and intra-species interactions, complex dynamics originate when the symmetry of the ground state is broken by phase separation. However, as driving the dynamics too quickly can result in unwanted excitations of the final state, we optimize the driven processes using shortcuts to adiabaticity, which are designed to reduce these excitations at the end of the interaction ramp, ensuring that the target eigenstate is reached. Full article
(This article belongs to the Special Issue Quantum Dynamics and Applications)
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15 pages, 3579 KiB  
Article
Quantum Optimal Control of Rovibrational Excitations of a Diatomic Alkali Halide: One-Photon vs. Two-Photon Processes
by Yuzuru Kurosaki and Keiichi Yokoyama
Universe 2019, 5(5), 109; https://doi.org/10.3390/universe5050109 - 8 May 2019
Cited by 1 | Viewed by 2095
Abstract
We investigated the roles of one-photon and two-photon processes in the laser-controlled rovibrational transitions of the diatomic alkali halide, 7Li37Cl. Optimal control theory calculations were carried out using the Hamiltonian, including both the one-photon and two-photon field-molecule interaction terms. Time-dependent [...] Read more.
We investigated the roles of one-photon and two-photon processes in the laser-controlled rovibrational transitions of the diatomic alkali halide, 7Li37Cl. Optimal control theory calculations were carried out using the Hamiltonian, including both the one-photon and two-photon field-molecule interaction terms. Time-dependent wave packet propagation was performed with both the radial and angular motions being treated quantum mechanically. The targeted processes were pure rotational and vibrational–rotational excitations: (v = 0, J = 0) → (v = 0, J = 2); (v = 0, J = 0) → (v = 1, J = 2). Total time of the control pulse was set to 2,000,000 atomic units (48.4 ps). In each control excitation process, weak and strong optimal fields were obtained by means of giving weak and strong field amplitudes, respectively, to the initial guess for the optimal field. It was found that when the field is weak, the control mechanism is dominated exclusively by a one-photon process, as expected, in both the targeted processes. When the field is strong, we obtained two kinds of optimal fields, one causing two-photon absorption and the other causing a Raman process. It was revealed, however, that the mechanisms for strong fields are not simply characterized by one process but rather by multiple one- and two-photon processes. It was also found that in the rotational excitation, (v = 0, J = 0) → (v = 0, J = 2), the roles of one- and two-photon processes are relatively distinct but in the vibrational–rotational excitation, (v = 0, J = 0) → (v = 1, J = 2), these roles are ambiguous and the cooperative effect associated with these two processes is quite large. Full article
(This article belongs to the Special Issue Quantum Dynamics and Applications)
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Review

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33 pages, 3389 KiB  
Review
Tripartite Entanglement: Foundations and Applications
by Márcio M. Cunha, Alejandro Fonseca and Edilberto O. Silva
Universe 2019, 5(10), 209; https://doi.org/10.3390/universe5100209 - 9 Oct 2019
Cited by 36 | Viewed by 5400
Abstract
We review some current ideas of tripartite entanglement. In particular, we consider the case representing the next level of complexity beyond the simplest (though far from trivial) one, namely the bipartite case. This kind of entanglement plays an essential role in understanding the [...] Read more.
We review some current ideas of tripartite entanglement. In particular, we consider the case representing the next level of complexity beyond the simplest (though far from trivial) one, namely the bipartite case. This kind of entanglement plays an essential role in understanding the foundations of quantum mechanics. It also allows for implementing several applications in the fields of quantum information processing and quantum computing. In this paper, we review the fundamental aspects of tripartite entanglement focusing on Greenberger–Horne–Zeilinger and W states for discrete variables. We discuss the possibility of using it as a resource to execute quantum protocols and present some examples in detail. Full article
(This article belongs to the Special Issue Quantum Dynamics and Applications)
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