Canonical and unitary transformation for a general time-dependent quadratic Hamiltonian system

2000 ◽  
Author(s):  
C. I. Um
Keyword(s):  
Hamiltonian System ◽  
Unitary Transformation ◽  
Time Dependent ◽  
Quadratic Hamiltonian ◽  
General Time

Relations of canonical and unitary transformations for a general time-dependent quadratic Hamiltonian system

1997 ◽  
Vol 55 (6) ◽  
pp. 4023-4029 ◽  
Author(s):  
Kyu-Hwang Yeon ◽  
Duk-Hyeon Kim ◽  
Chung-In Um ◽  
Thomas F. George ◽  
Lakshmi N. Pandey
Keyword(s):  
Hamiltonian System ◽  
Time Dependent ◽  
Unitary Transformations ◽  
Quadratic Hamiltonian ◽  
General Time

scholarly journals Exact time-dependent decoherence factor and its adiabatic classical limit

2003 ◽  
Vol 81 (10) ◽  
pp. 1185-1191
Author(s):  
J -Q Shen ◽  
P Chen ◽  
H Mao
Keyword(s):  
Invariant Theory ◽  
Geometric Phase ◽  
Classical Limit ◽  
Unitary Transformation ◽  
Time Dependent ◽  
Quantum Decoherence ◽  
Dynamical Models ◽  
Complete Set ◽  
General Time ◽  
03.65 Ge

The present paper finds the complete set of exact solutions of the general time-dependent dynamical models for quantum decoherence, by making use of the Lewis–Riesenfeld invariant theory and the invariant-related unitary transformation formulation. Based on this, the general explicit expression for the decoherence factor is then obtained and the adiabatic classical limit of an illustrative example is discussed. The result (i.e., the adiabatic classical limit) obtained in this paper is consistent with what is obtained by other authors, and furthermore we obtain more general results concerning time-dependent nonadiabatic quantum decoherence. It is shown that the invariant theory is appropriate for treating both the time-dependent quantum decoherence and the geometric phase factor. PACS Nos.: 03.65.Ge, 03.65.Bz

THE QUADRATIC TIME-DEPENDENT HAMILTONIAN: EVOLUTION OPERATOR, SQUEEZING REGIONS IN PHASE SPACE AND TRAJECTORIES

1994 ◽  
Vol 08 (11n12) ◽  
pp. 1563-1576 ◽  
Author(s):  
S.S. MIZRAHI ◽  
M.H.Y. MOUSSA ◽  
B. BASEIA
Keyword(s):  
Phase Space ◽  
Unitary Transformation ◽  
Uniform Magnetic Field ◽  
Evolution Operator ◽  
Single Mode ◽  
Time Dependent ◽  
Special Cases ◽  
Complete Set ◽  
Hamiltonian Evolution ◽  
General Time

We consider the most general Time-Dependent (TD) quadratic Hamiltonian written in terms of the bosonic operators a and a+, which may represent either a charged particle subjected to a harmonic motion, immersed in a TD uniform magnetic field, or a single mode photon field going through a squeezing medium. We solve the TD Schrödinger equation by a method that uses, sequentially, a TD unitary transformation and the diagonalization of a TD invariant, and we verify that the exact solution is a complete set of TD states. We also obtain the evolution operator which is essential to express operators in the Heisenberg picture. The variances of the quadratures are calculated and a phase space of parameters introduced, in which we identify squeezing regions. The results for some special cases are presented and as an illustrative example the parametric oscillator is revisited and the trajectories in phase space drawn.

Exact quantum theory of a time-dependent bound quadratic Hamiltonian system

1993 ◽  
Vol 48 (4) ◽  
pp. 2716-2720 ◽  
Author(s):  
Kyu Hwang Yeon ◽  
Kang Ku Lee ◽  
Chung In Um ◽  
Thomas F. George ◽  
Lakshmi N. Pandey
Keyword(s):  
Quantum Theory ◽  
Hamiltonian System ◽  
Time Dependent ◽  
Exact Quantum ◽  
Quadratic Hamiltonian
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