BROKEN UNITARY SYMMETRIES AND FERMI–DIRAC STATISTICS

2007 ◽  
Vol 22 (40) ◽  
pp. 3037-3045 ◽  
Author(s):  
M. CALIXTO ◽  
V. ALDAYA
Keyword(s):  
Thermal Radiation ◽  
Coherent States ◽  
Quantum Systems ◽  
Broken Symmetry ◽  
Particle Theory ◽  
N Level ◽  
Zero Modes ◽  
Dirac Type ◽  
Symmetry Transformations ◽  
The Many

The existence of degenerated quantum vacua (coherent states of zero modes), for N-level quantum systems, leads to a breakdown of the original unitary U (N) symmetry in the many-particle theory. The action of some spontaneously broken symmetry transformations destabilize these pseudo-vacua and make them radiate. We study the structure of this thermal radiation, which turns out to be of Fermi–Dirac type.

Non-integrability of the optimal control problem for n-level quantum systems

2017 ◽  
Vol 50 (17) ◽  
pp. 175202 ◽  
Author(s):  
Guillaume Duval ◽  
Andrzej Maciejewski ◽  
Witold Respondek
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Quantum Systems ◽  
N Level

scholarly journals Residual Entropy and Critical Behavior of Two Interacting Boson Species in a Double Well

2017 ◽  
Author(s):  
Fabio Lingua ◽  
Andrea Richaud ◽  
Vittorio Penna
Keyword(s):  
Coherent States ◽  
Variational Approach ◽  
Entanglement Entropy ◽  
Quantum Systems ◽  
Residual Entropy ◽  
Zero Temperature ◽  
Temperature Scenario ◽  
Physical Insight ◽  
Insight Into ◽  
Specific Quantum

Motivated by the importance of entanglement and correlation indicators in the analysis of quantum systems, we study the equilibrium and the residual entropy in a two-species Bose Hubbard dimer when the spatial phase separation of the two species takes place. We consider both the zero and non-zero-temperature regime. We present different kinds of residual entropies (each one associated to a different way of partitioning the system), and we show that they strictly depend on the specific quantum phase characterizing the two species (supermixed, mixed or demixed) even at finite temperature. To provide a deeper physical insight into the zero-temperature scenario, we apply the fully-analytical variational approach based on su(2) coherent states and provide a considerbly good approximation of the entanglement entropy. Finally, we show that the effectiveness of residual entropy as a critical indicator at non-zero temperature is unchanged when considering a restricted combination of energy eigenstates.

scholarly journals Quantum computing and second quantization

2017 ◽  
Vol 26 (03) ◽  
pp. 1741006 ◽  
Author(s):  
Hanna Makaruk
Keyword(s):  
Quantum Computing ◽  
Approximate Method ◽  
Quantum Systems ◽  
General Idea ◽  
Entangled States ◽  
Quantum Computers ◽  
Second Quantization ◽  
Particle Arrangement ◽  
The Many

Quantum computers by their nature are many particle quantum systems. Both the many-particle arrangement and being quantum are necessary for the existence of the entangled states, which are responsible for the parallelism of the quantum computers. Second quantization is a very important approximate method of describing such systems. This lecture will present the general idea of the second quantization, and discuss shortly some of the most important formulations of second quantization.

On observability of N-level quantum systems

1985 ◽  
Vol 21 (1) ◽  
pp. 101-109 ◽  
Author(s):  
A. Jamiolkowski
Keyword(s):  
Quantum Systems ◽  
N Level

scholarly journals Hubbard-Stratonovich-like Transformations for Few-Body Interactions

2018 ◽  
Vol 175 ◽  
pp. 11012
Author(s):  
Christopher Körber ◽  
Evan Berkowitz ◽  
Thomas Luu
Keyword(s):  
Perturbation Theory ◽  
Great Accuracy ◽  
Quantum Systems ◽  
Collective Phenomena ◽  
Many Body ◽  
Chiral Perturbation ◽  
Body Level ◽  
The Many ◽  
Three Body ◽  
Number Of Particles

Through the development of many-body methodology and algorithms, it has become possible to describe quantum systems composed of a large number of particles with great accuracy. Essential to all these methods is the application of auxiliary fields via the Hubbard-Stratonovich transformation. This transformation effectively reduces two-body interactions to interactions of one particle with the auxiliary field, thereby improving the computational scaling of the respective algorithms. The relevance of collective phenomena and interactions grows with the number of particles. For many theories, e.g. Chiral Perturbation Theory, the inclusion of three-body forces has become essential in order to further increase the accuracy on the many-body level. In this proceeding, the an-alytical framework for establishing a Hubbard-Stratonovich-like transformation, which allows for the systematic and controlled inclusion of contact three-and more-body inter-actions, is presented.

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