Optimal system-specific coherent states for excited state calculations of quantum systems

2021 ◽  
pp. 139016
Author(s):  
Chi-En Li ◽  
Ching-Teh Li ◽  
Chia-Chun Chou
Keyword(s):  
Excited State ◽  
Coherent States ◽  
Quantum Systems ◽  
Optimal System

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.

Correlated coherent states and emission by quantum systems

1993 ◽  
Vol 14 (3) ◽  
pp. 223-236
Author(s):  
V. V. Dodonov ◽  
V. I. Man'ko ◽  
O. V. Man'ko
Keyword(s):  
Coherent States ◽  
Quantum Systems

scholarly journals Geometry of variational methods: dynamics of closed quantum systems

2020 ◽  
Vol 9 (4) ◽  
Author(s):  
Lucas Hackl ◽  
Tommaso Guaita ◽  
Tao Shi ◽  
Jutho Haegeman ◽  
Eugene Demler ◽  
...  
Keyword(s):  
Variational Methods ◽  
Time Evolution ◽  
Coherent States ◽  
Geometric Approach ◽  
Quantum Systems ◽  
Imaginary Time ◽  
Excitation Spectra ◽  
Spectral Functions ◽  
Geometric Framework ◽  
Gaussian States

We present a systematic geometric framework to study closed quantum systems based on suitably chosen variational families. For the purpose of (A) real time evolution, (B) excitation spectra, (C) spectral functions and (D) imaginary time evolution, we show how the geometric approach highlights the necessity to distinguish between two classes of manifolds: Kähler and non-Kähler. Traditional variational methods typically require the variational family to be a Kähler manifold, where multiplication by the imaginary unit preserves the tangent spaces. This covers the vast majority of cases studied in the literature. However, recently proposed classes of generalized Gaussian states make it necessary to also include the non-Kähler case, which has already been encountered occasionally. We illustrate our approach in detail with a range of concrete examples where the geometric structures of the considered manifolds are particularly relevant. These go from Gaussian states and group theoretic coherent states to generalized Gaussian states.

scholarly journals Improving Continuous Variable Quantum Secret Sharing with Weak Coherent States

2020 ◽  
Vol 10 (7) ◽  
pp. 2411
Author(s):  
Yijun Wang ◽  
Bing Jia ◽  
Yun Mao ◽  
Xuelin Wu ◽  
Ying Guo
Keyword(s):  
Secret Sharing ◽  
Coherent States ◽  
Security Analysis ◽  
Quantum Secret Sharing ◽  
Continuous Variable ◽  
Quantum Systems ◽  
Phase Modulators ◽  
Security Proof ◽  
Optical Modes ◽  
Threshold Schemes

Quantum secret sharing (QSS) can usually realize unconditional security with entanglement of quantum systems. While the usual security proof has been established in theoretics, how to defend against the tolerable channel loss in practices is still a challenge. The traditional ( t , n ) threshold schemes are equipped in situation where all participants have equal ability to handle the secret. Here we propose an improved ( t , n ) threshold continuous variable (CV) QSS scheme using weak coherent states transmitting in a chaining channel. In this scheme, one participant prepares for a Gaussian-modulated coherent state (GMCS) transmitted to other participants subsequently. The remaining participants insert independent GMCS prepared locally into the circulating optical modes. The dealer measures the phase and the amplitude quadratures by using double homodyne detectors, and distributes the secret to all participants respectively. Special t out of n participants could recover the original secret using the Lagrange interpolation and their encoded random numbers. Security analysis shows that it could satisfy the secret sharing constraint which requires the legal participants to recover message in a large group. This scheme is more robust against background noise due to the employment of double homodyne detection, which relies on standard apparatuses, such as amplitude and phase modulators, in favor of its potential practical implementations.

Correlated and Squeezed Coherent States of Nonstationary Quantum Systems

1993 ◽  
pp. 205-208
Author(s):  
V. V. Dodonov ◽  
A. V. Klimow ◽  
V. I. Man’ko
Keyword(s):  
Coherent States ◽  
Quantum Systems

VECTOR COHERENT STATES AND NON-ABELIAN GAUGE STRUCTURES IN QUANTUM MECHANICS

1990 ◽  
Vol 05 (22) ◽  
pp. 4311-4331 ◽  
Author(s):  
G. GIAVARINI ◽  
E. ONOFRI
Keyword(s):  
Quantum Mechanics ◽  
Lie Group ◽  
Coherent States ◽  
Quantum Systems ◽  
Semisimple Lie Group ◽  
Abelian Gauge ◽  
Geometric Properties ◽  
Generalized Coherent States ◽  
Abelian Case ◽  
Vector Coherent States

We set the general formalism for calculating Berry's phase in quantum systems with Hamiltonian belonging to the algebra of a semisimple Lie group of any rank in the framework of generalized coherent states. Within this approach the geometric properties of Berry's connection are also studied, both in the Abelian and non-Abelian cases. In particular we call attention to the non-Abelian case where we make use of a vectorial generalization of coherent states. In this respect a thorough and self-contained exposition of the formalism of vector coherent states is given. The specific examples of the groups SU(3) and Sp(2) are worked out in detail.

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