Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Modern Physics Letters A

PHASE OPERATOR AND PHASE STATE IN THERMO FIELD DYNAMICS

Hong-Yi Fan, Nian-Quan Jiang

Published May 20, 2009• 1 citation
Publisher

Abstract

We extend the Susskind–Glogower phase operator and phase state in quantum optics to thermo field dynamics (TFD). Based on the thermo entangled state representation, we introduce thermo excitation and de-excitation operators with which the phase operator and phase state in TFD can be constructed. The phase state treated as a limiting case of a new SU(1, 1) coherent states is also exhibited.

DOI
10.1142/s0217732309028461

Related papers

NEW THERMO EXCITATION STATES AND OPERATIONS IN THERMO FIELD DYNAMICS

Xuefen Xu, Shiqun Zhu

According to the thermo field dynamics proposed by Takahashi–Umezawa, the Hamiltonian h = a†a - ã†ã and h|n, ñ〉 = 0 of the original optical field excitation state |n〉 and its tilde state |ñ〉 in the Hilbert space cannot embody the eigenvalue spectrum of h. To avoid the weakness, new thermo excitation states are successfully constructed by introducing appropriate thermo excitation operators. It is noted that they are entangled states. Applications of the new thermo excitation state in constructing new thermo squeezed state and phase state are also presented.

Modern Physics Letters A•Mar 28, 2009•0 citations

Thermo Wigner operator in thermo field dynamics: its introduction and application

Hong-Yi Fan, Nian-Quan Jiang

Because in thermo-field dynamics (TFD) the thermo-operator has a neat expression in the thermo-entangled state representation, we need to introduce the thermo-Wigner operator (THWO) in the same representation. We derive the THWO in a direct way, which brings much conveniece to calculating the Wigner functions of thermo states in TFD. We also discuss the condition for existence of a wavefunction corresponding to a given Wigner function in the context of TFD by using the explicit form of the THWO.

Physica Scripta•Oct 1, 2008•7 citations

Phase State as a Limiting Case of SU(1,1) Coherent State

Zhisong Yu, Fan Hong‐Yi

We show that the Susskind—Glogower phase state is a limiting case of a kind of SU(1,1) coherent states. By analogy, based on the bipartite entangled state representation (ESR) we demonstrate that an appropriate SU(1,1) coherent state composed of the two-mode unitary phase operator also leads to a new phase state in two-mode Fock space. is diagonalized in the ESR.

Communications in Theoretical Physics•Jan 1, 2009•1 citation

Phase operators for the electromagnetic field by squeezed-state theory

Robert Lynch

A new set of phase operators for the electromagnetic field has been defined by an extension of squeezed-state theory. In several cases these operators have similar or the same properties as the previously defined (Susskind–Glogower) operators. However, the new operators also have unique properties of their own. The expectation values of the phase operators have been found for a squeezed state and been shown to reduce to the expected classical values in the limit of small amounts of squeezing and large field excitation.

Journal of the Optical Society of America B•Jul 1, 1986•25 citations

THE MIXED COHERENT STATE REPRESENTATION OF THE DENSITY OPERATOR IN THERMO-FIELD DYNAMICS

Heng Fan, Hai-liang Lu

In the framework of thermo-field dynamics, invented by Umezawa et al., we construct a mixed coherent state representation of density operator ρ. This new representation is useful because it provides an approach to retrieve ρ from its c-number solution of master equations in the entangled state representation.

Modern Physics Letters B•Feb 10, 2007•20 citations

Inverse operator representations of quantum phase

G. M. Saxena

We define quantum phase in terms of inverses of annihilation and creation operators. We show that like Susskind - Glogower phase operators, the measured phase operators and the unitary phase operators can be defined in terms of the inverse operators. However, for the unitary phase operator the Hilbert space includes the negative energy states. The quantum phase in inverse operator representation may find the applications in the field of quantum optics particularly in the squeezed states.

arXiv:0803.2094•Mar 14, 2008•0 citations
We extend the Susskind–Glogower phase operator and phase state in quantum optics to thermo field dynamics (TFD). Based on the thermo entangled state representation, we introduce thermo excitation and de-excitation operators with which the phase operator and phase state in TFD can be constructed. The phase state treated as a limiting case of a new SU(1, 1) coherent states is also exhibited.
According to the thermo field dynamics proposed by Takahashi–Umezawa, the Hamiltonian h = a†a - ã†ã and h|n, ñ〉 = 0 of the original optical field excitation state |n〉 and its tilde state |ñ〉 in the Hilbert space cannot embody the eigenvalue spectrum of h. To avoid the weakness, new thermo excitation states are successfully constructed by introducing appropriate thermo excitation operators. It is noted that they are entangled states. Applications of the new thermo excitation state in constructing new thermo squeezed state and phase state are also presented.
A new set of phase operators for the electromagnetic field has been defined by an extension of squeezed-state theory. In several cases these operators have similar or the same properties as the previously defined (Susskind–Glogower) operators. However, the new operators also have unique properties of their own. The expectation values of the phase operators have been found for a squeezed state and been shown to reduce to the expected classical values in the limit of small amounts of squeezing and large field excitation.