scholarly journals Application of the theory of open quantum systems in nuclear physics

2019 ◽  
Vol 49 ◽  
pp. 1960008
Author(s):  
V. V. Sargsyan ◽  
Z. Kanokov ◽  
G. G. Adamian ◽  
N. V. Antonenko
Keyword(s):  
Nuclear Physics ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Reduced Density Matrix ◽  
Quantum Model ◽  
Matrix Formalism ◽  
Capture Process ◽  
Projectile Nucleus ◽  
Density Matrix Formalism ◽  
Reduced Density

Projectile-nucleus capture by a target nucleus at bombarding energies in the vicinity of the Coulomb barrier is treated with the reduced-density-matrix formalism. The effects of dissipation and fluctuations on the capture process are taken self-consistently into account within the quantum model suggested. The excitation functions for the capture in the reactions [Formula: see text]O, [Formula: see text]F, [Formula: see text]Mg, [Formula: see text]Si, [Formula: see text]S, [Formula: see text]Ca, [Formula: see text]Ti, [Formula: see text]Cr [Formula: see text] [Formula: see text]Pb are calculated and compared with the experimental data.

scholarly journals Complexity from the reduced density matrix: a new diagnostic for chaos

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Arpan Bhattacharyya ◽  
S. Shajidul Haque ◽  
Eugene H. Kim
Keyword(s):  
Density Matrix ◽  
Quantum Chaos ◽  
Open Quantum Systems ◽  
Circuit Complexity ◽  
Quantum Systems ◽  
Harmonic Oscillators ◽  
Quantum Circuits ◽  
Reduced Density Matrix ◽  
Evolution Of Complexity ◽  
Reduced Density

Abstract We investigate circuit complexity to characterize chaos in multiparticle quantum systems. In the process, we take a stride to analyze open quantum systems by using complexity. We propose a new diagnostic of quantum chaos from complexity based on the reduced density matrix by exploring different types of quantum circuits. Through explicit calculations on a toy model of two coupled harmonic oscillators, where one or both of the oscillators are inverted, we demonstrate that the evolution of complexity is a possible diagnostic of chaos.

scholarly journals Quantum collisional thermostats

2022 ◽  
Author(s):  
Jorge Tabanera ◽  
Inés Luque ◽  
Samuel L. Jacob ◽  
Massimiliano Esposito ◽  
Felipe Barra ◽  
...  
Keyword(s):  
Open Quantum Systems ◽  
Formal Solution ◽  
Scattering Problem ◽  
Approximate Solutions ◽  
Quantum Systems ◽  
Matrix Formalism ◽  
External Agent ◽  
Far From Equilibrium ◽  
Transfer Matrix Formalism ◽  
Scattering Map

Abstract Collisional reservoirs are becoming a major tool for modelling open quantum systems. In their simplest implementation, an external agent switches on, for a given time, the interaction between the system and a specimen from the reservoir. Generically, in this operation the external agent performs work onto the system, preventing thermalization when the reservoir is at equilibrium. One can recover thermalization by considering an autonomous global setup where the reservoir particles colliding with the system possess a kinetic degree of freedom. The drawback is that the corresponding scattering problem is rather involved. Here, we present a formal solution of the problem in one dimension and for flat interaction potentials. The solution is based on the transfer matrix formalism and allows one to explore the symmetries of the resulting scattering map. One of these symmetries is micro-reversibility, which is a condition for thermalization. We then introduce two approximations of the scattering map that preserve these symmetries and, consequently, thermalize the system. These relatively simple approximate solutions constitute models of quantum thermostats and are useful tools to study quantum systems in contact with thermal baths. We illustrate their accuracy in a specific example, showing that both are good approximations of the exact scattering problem even in situations far from equilibrium. Moreover, one of the models consists of the removal of certain coherences plus a very specific randomization of the interaction time. These two features allow one to identify as heat the energy transfer due to switching on and off the interaction. Our results prompt the fundamental question of how to distinguish between heat and work from the statistical properties of the exchange of energy between a system and its surroundings.

scholarly journals Complex Time Evolution of Open Quantum Systems

2011 ◽  
Vol 18 (03) ◽  
pp. 261-288
Author(s):  
C. N. Gagatsos ◽  
A. I. Karanikas ◽  
G. I. Kordas
Keyword(s):  
Time Evolution ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Compact Representation ◽  
Complex Time ◽  
Open Quantum ◽  
Time Formalism ◽  
Technical Details ◽  
Set Up ◽  
Reduced Density

We combine, in a single set-up, complex time parametrization in path integration, and closed time formalism of non-equilibrium field theories to produce a compact representation of time evolution of the reduced density matrix. In this framework we introduce a cluster-type expansion that facilitates perturbative and non-petrurbative calculations in the realm of open quantum systems. The technical details of some very simple examples are discussed.

scholarly journals Quantum States of Hierarchic Systems

2003 ◽  
Vol 01 (02) ◽  
pp. 269-278 ◽  
Author(s):  
Mikhail V. Altaisky
Keyword(s):  
Hilbert Space ◽  
Density Matrix ◽  
Degrees Of Freedom ◽  
Quantum Systems ◽  
Quantum States ◽  
Matrix Formalism ◽  
Density Matrix Formalism ◽  
Theory Of Measurements ◽  
Novel Method ◽  
Chemical And Biological Systems

The density matrix formalism which is widely used in the theory of measurements, quantum computing, quantum description of chemical and biological systems always implies the averaging over all states of the environment. In practice this is impossible because the environment of the system is the complement of this system to the whole Universe and contains infinitely many degrees of freedom. A novel method of construction density matrix which implies the averaging only over the direct environment is proposed. The Hilbert space of state vectors for the hierarchic quantum systems is constructed.

DENSITY MATRIX FORMALISM, DOUBLE-SPACE AND THERMO FIELD DYNAMICS IN NON-EQUILIBRIUM DISSIPATIVE SYSTEMS

1991 ◽  
Vol 05 (11) ◽  
pp. 1821-1842 ◽  
Author(s):  
MASUO SUZUKI
Keyword(s):  
Density Matrix ◽  
Quantum Systems ◽  
Harmonic Oscillators ◽  
Matrix Formalism ◽  
Thermo Field Dynamics ◽  
Density Matrix Formalism ◽  
Space Formulation ◽  
Double Space ◽  
Dissipative Quantum Systems ◽  
Non Equilibrium

General relationship among the density matrix formalism, the double-space formulation and thermo field dynamics is discussed in non-equilibrium dissipative quantum systems. The concept of weakly equivalent operators in the double space formulation is introduced to review many well-known results and it is shown to be useful in mapping between the density matrix formalism and the double space formulation. A new non-equilibrium thermo field dynamics is formulated to discuss dissipative quantum systems. A simple example of damped harmonic oscillators is discussed in the present representation.

scholarly journals Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
M. Merkli ◽  
G. P. Berman ◽  
F. Borgonovi ◽  
V. I. Tsifrinovich
Keyword(s):  
Quantum Information ◽  
Open Quantum System ◽  
Quantum Systems ◽  
Time Dependent ◽  
Reduced Density Matrix ◽  
Macroscopic Quantum ◽  
Thermal Environments ◽  
Energy Conserving ◽  
Reduced Density ◽  
Macroscopic Quantum Systems

We consider an open quantum system ofNnot directly interacting spins (qubits) in contact with both local and collective thermal environments. The qubit-environment interactions are energy conserving. We trace out the variables of the thermal environments andN−2qubits to obtain the time-dependent reduced density matrix for two arbitrary qubits. We numerically simulate the reduced dynamics and the creation of entanglement (concurrence) as a function of the parameters of the thermal environments and the number of qubits,N. Our results demonstrate that the two-qubit entanglement generally decreases asNincreases. We show analytically that, in the limitN→∞, no entanglement can be created. This indicates that collective thermal environments cannot create two-qubit entanglement when many qubits are located within a region of the size of the environment coherence length. We discuss possible relevance of our consideration to recent quantum information devices and biosystems.

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