scholarly journals Quantum Mechanical Engine for the Quantum Rabi Model

Entropy ◽  
2018 ◽  
Vol 20 (10) ◽  
pp. 767 ◽  
Author(s):  
Gabriel Barrios ◽  
Francisco Peña ◽  
Francisco Albarrán-Arriagada ◽  
Patricio Vargas ◽  
Juan Retamal
Keyword(s):  
Coupling Strength ◽  
High Efficiency ◽  
Strength Parameter ◽  
Quantum Mechanical ◽  
Level System ◽  
Expectation Value ◽  
Resonator Frequency ◽  
Rabi Model ◽  
Parameter Values ◽  
System Frequency

We consider a purely mechanical quantum cycle comprised of adiabatic and isoenergetic processes. In the latter, the system interacts with an energy bath keeping constant the expectation value of the Hamiltonian. In this work, we study the performance of the quantum cycle for a system described by the quantum Rabi model for the case of controlling the coupling strength parameter, the resonator frequency, and the two-level system frequency. For the cases of controlling either the coupling strength parameter or the resonator frequency, we find that it is possible to closely approach to maximal unit efficiency when the parameter is sufficiently increased in the first adiabatic stage. In addition, for the first two cases the maximal work extracted is obtained at parameter values corresponding to high efficiency, which constitutes an improvement over current proposals of this cycle.

scholarly journals Isoenergetic Cycle for the Quantum Rabi Model

2018 ◽  
Author(s):  
G. Alvarado Barrios ◽  
Francisco J. Peña ◽  
F. Albarrán-Arriagada ◽  
P. Vargas ◽  
J. C. Retamal
Keyword(s):  
Power Law ◽  
Coupling Strength ◽  
High Efficiency ◽  
Strength Parameter ◽  
Level System ◽  
Expectation Value ◽  
Resonator Frequency ◽  
Rabi Model ◽  
Parameter Values ◽  
System Frequency

The isoenergetic cycle is a purely mechanical cycle comprised of adiabatic and isoenergetic processes. In the latter the system interacts with an energy bath keeping constant the expectation value of the Hamiltonian. This cycle has been mostly studied in systems consisting of particles confined in a power-law trap. In this work we study the performance of the isoenergetic cycle for a system described by the quantum Rabi model for the case of controlling the coupling strength parameter, the resonator frequency and the two-level system frequency. For the cases of controlling either the coupling strength parameter or the resonator frequency, we find that it is possible to closely approach to maximal unit efficiency when the parameter is sufficiently increased in the first adiabatic stage. In addition, for the first two cases the maximal work extracted is obtained at parameter values corresponding to high efficiency which constitutes an improvement over current proposals of this cycle.

scholarly journals Quantum resources for energy storage

2020 ◽  
Vol 230 ◽  
pp. 00003 ◽  
Author(s):  
Dario Ferraro ◽  
Michele Campisi ◽  
Gian Marcello Andolina ◽  
Vittorio Pellegrini ◽  
Marco Polini
Keyword(s):  
Energy Storage ◽  
Cavity Mode ◽  
Quantum Mechanical ◽  
Double Quantum ◽  
Level System ◽  
Close Proximity ◽  
Two Level Systems ◽  
Quantum Mechanical Effects ◽  
The One ◽  
Superradiant Phase

Recently the possibility to exploit quantum-mechanical effects to increase the performance of energy storage has raised a great interest. It consists of N two-level systems coupled to a single photonic mode in a cavity. We demonstrate the emergence of a quantum advantage in the charging power on this collective model (Dicke Quantum Battery) with respect to the one in which each two-level system is coupled to its own separate cavity mode (Rabi Quantum Battery). Moreover, we discuss the model of a Quantum Supercapacitor. This consists of two chains, one containing electrons and the other one holes, hosted by arrays of double quantum dots. The two chains are in close proximity and embedded in the same photonic cavity, in the same spirit of the Dicke model. We find the phase diagram of this model showing that, when transitioning from the ferro/antiferromagnetic to the superradiant phase, the quantum capacitance of the model is greatly enhanced.

scholarly journals Magnetic reversal dynamics of a quantum system on a picosecond timescale

2015 ◽  
Vol 6 ◽  
pp. 1946-1956 ◽  
Author(s):  
Nikolay V Klenov ◽  
Alexey V Kuznetsov ◽  
Igor I Soloviev ◽  
Sergey V Bakurskiy ◽  
Olga V Tikhonova
Keyword(s):  
Magnetic Moment ◽  
Magnetization Reversal ◽  
Quantum Mechanical ◽  
Magnetic Reversal ◽  
Level System ◽  
Macroscopic Theory ◽  
Atomic Systems ◽  
Quantum Mechanical Description ◽  
Classical Behavior ◽  
Flux Qubit

We present our approach for a consistent, fully quantum mechanical description of the magnetization reversal process in natural and artificial atomic systems by means of short magnetic pulses. In terms of the simplest model of a two-level system with a magnetic moment, we analyze the possibility of a fast magnetization reversal on the picosecond timescale induced by oscillating or short unipolar magnetic pulses. We demonstrate the possibility of selective magnetization reversal of a superconducting flux qubit using a single flux quantum-based pulse and suggest a promising, rapid Λ-scheme for resonant implementation of this process. In addition, the magnetization reversal treatment is fulfilled within the framework of the macroscopic theory of the magnetic moment, which allows for the comparison and explanation of the quantum and classical behavior.

scholarly journals DYNAMICS OF A LARGE-SPIN-BOSON SYSTEM IN THE STRONG COUPLING REGIME

2003 ◽  
Vol 17 (28) ◽  
pp. 5489-5493 ◽  
Author(s):  
TILL VORRATH ◽  
TOBIAS BRANDES ◽  
BERNHARD KRAMER
Keyword(s):  
Strong Coupling ◽  
Collective Effects ◽  
Strong Coupling Regime ◽  
Markov Approximation ◽  
Expectation Value ◽  
Maximum Value ◽  
Two Level Systems ◽  
Highly Correlated ◽  
Parameter Values ◽  
Large Spin

We investigate collective effects of an ensemble of biased two-level systems interacting with a bosonic bath in the strong coupling regime. The two level systems are described by a large pseudo-spin J. An equation for the expectation value M(t) of the z-component of the pseudo spin is derived and solved numerically for an ohmic bath at T=0. In case of a large cut-off frequency of the spectral function, a Markov approximation is justified and an analytical solution is presented. We find that M(t) relaxes towards a highly correlated state with maximum value ±J for large times. However, this relaxation is extremely slow for most parameter values so as if the system was "frozen in" by interaction with the bosonic bath.

scholarly journals Controlled On-Chip Single-Photon Transfer Using Photonic Crystal Coupled-Cavity Waveguides

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Hubert Pascal Seigneur ◽  
Matthew Weed ◽  
Michael Niklaus Leuenberger ◽  
Winston Vaughan Schoenfeld
Keyword(s):  
High Efficiency ◽  
Nearest Neighbor ◽  
Single Photon ◽  
Tight Binding ◽  
Quantum Mechanical ◽  
Single Photons ◽  
Quantum Network ◽  
On Chip ◽  
Quantum Mechanical Approach ◽  
Coupled Cavity

To the end of realizing a quantum network on-chip, single photons must be guided consistently to their proper destination both on demand and without alteration to the information they carry. Coupled cavity waveguides are anticipated to play a significant role in this regard for two important reasons. First, these structures can easily be included within fully quantum-mechanical models using the phenomenological description of the tight-binding Hamiltonian, which is simply written down in the basis of creation and annihilation operators that move photons from one quasimode to another. This allows for a deeper understanding of the underlying physics and the identification and characterization of features that are truly critical to the behavior of the quantum network using only a few parameters. Second, their unique dispersive properties together with the careful engineering of the dynamic coupling between nearest neighbor cavities provide the necessary control for high-efficiency single-photon on-chip transfer. In this publication, we report transfer efficiencies in the upwards of 93% with respect to a fully quantum-mechanical approach and unprecedented 77% in terms of transferring the energy density contained in a classical quasibound mode from one cavity to another.

scholarly journals ZN symmetric chiral Rabi model: A new N-level system

2014 ◽  
Vol 347 ◽  
pp. 122-129 ◽  
Author(s):  
Yao-Zhong Zhang
Keyword(s):  
Level System ◽  
Rabi Model

scholarly journals Generalization of Brillouin theorem for the non-relativistic electronic Schrödinger equation in relation to coupling strength parameter, and its consequences in single determinant basis sets for configuration interactions

2017 ◽  
Author(s):  
Sandor Kristyan
Keyword(s):  
Schrödinger Equation ◽  
Coupling Strength ◽  
Schrodinger Equation ◽  
Basis Set ◽  
Basis Sets ◽  
Single Line ◽  
Strength Parameter ◽  
Physical Case ◽  
Ci Calculations

<p> The Brillouin theorem has been generalized for the extended non-relativistic electronic Hamiltonian (H<sub>Ñ</sub>+ H<sub>ne</sub>+ aH<sub>ee</sub>) in relation to coupling strength parameter (a), as well as for the configuration interactions (CI) formalism in this respect. For a computation support, we have made a particular modification of the SCF part in the Gaussian package: essentially a single line was changed in an SCF algorithm, wherein the operator r<sub>ij</sub><sup>-1</sup> was overwritten as r<sub>ij</sub><sup>-1</sup> ® ar<sub>ij</sub><sup>-1</sup>, and “a” was used as input. The case a=0 generates an orto-normalized set of Slater determinants which can be used as a basis set for CI calculations for the interesting physical case a=1, removing the known restriction by Brillouin theorem with this trick. The latter opens a door from the theoretically interesting subject of this work toward practice. </p>

scholarly journals The cosmological constant of emergent spacetime in the Newtonian approximation

2020 ◽  
Vol 29 (13) ◽  
pp. 2050093
Author(s):  
J. C. Castro-Palacio ◽  
P. Fernández de Córdoba ◽  
J. M. Isidro
Keyword(s):  
Cosmological Constant ◽  
Quantum Mechanical ◽  
Nonrelativistic Quantum ◽  
Expectation Value ◽  
Simple Quantum ◽  
Emergent Spacetime ◽  
Nonrelativistic Quantum Mechanics ◽  
The Given ◽  
The Universe ◽  
Matter Fields

We present a simple quantum-mechanical estimate of the cosmological constant of a Newtonian Universe. We first mimic the dynamics of a Newtonian spacetime by means of a nonrelativistic quantum mechanics for the matter contents of the Universe (baryonic and dark) within a fixed (i.e. nondynamical) Euclidean spacetime. Then we identify an operator that plays, on the matter states, a role analogous to that played by the cosmological constant. Finally, we prove that there exists a quantum state for the matter fields, in which the above-mentioned operator has an expectation value equal to the cosmological constant of the given Newtonian Universe.

scholarly journals Electronic Transport Through Double Quantum Dot Coupled to Majorana Bound States and Ferromagnetic Leads

2021 ◽  
Vol 8 ◽  
Author(s):  
Li-Wen Tang ◽  
Wei-Guo Mao
Keyword(s):  
Quantum Dot ◽  
Coupling Strength ◽  
Bound States ◽  
High Efficiency ◽  
Energy Levels ◽  
Electrical Current ◽  
Function Technique ◽  
Double Quantum ◽  
Majorana Bound States ◽  
Double Quantum Dot

We have studied theoretically the properties of electrical current and tunnel magnetoresistance (TMR) through a serially connected double quantum dot (DQD) sandwiched between two ferromagnetic leads by using the nonequilibrium Green’s function technique. We consider that each of the DQD couples to one mode of the Majorana bound states (MBSs) formed at the ends of a topological superconductor nanowire with spin-dependent coupling strength. By adjusting the sign of the spin polarization of dot–MBS coupling strength and the arrangement of magnetic moments of the two leads, the currents’ magnitude can be effectively enhanced or suppressed. Under some conditions, a negative TMR emerges which is useful in detection of the MBSs, a research subject currently under extensive investigations. Moreover, the amplitude of the TMR can be adjusted in a large regime by variation of several system parameters, such as direct hybridization strength between the MBSs or the dots and the positions of the dots’ energy levels. Such tunable currents and TMR may also find use in high-efficiency spintronic devices or information processes.

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