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

Frontiers of Physics

Entropy evolution law of general quadratic state in a laser channel

Xiang-Guo Meng, Bao-Long Liang, Jian-Ming Liu, Xu-Cong Zhou

Published Dec 4, 2024• 9 citations
Publisher

Abstract

Using the integration within ordered products, we obtain the analytical density-operator evolution of the general quadratic state ρ 0 in a laser channel, which always maintains the same form as the initial density operator ρ 0. Introducing the differential representation of the von-Neumann entropy and two important resemble formulas, we analytically and numerically investigate the entropy evolution of the state ρ 0 in a laser channel, which is determined by not only the competition of the gain and loss of the laser channel, but also the coefficients α, β of the initial quadratic state ρ 0.

DOI
10.15302/frontphys.2025.022205

Related papers

Analytical and numerical investigations of displaced thermal state evolutions in a laser process

Chuan-Xun Du, Xiang‐Gao Meng, Ran Zhang +1 more

We investigate how displaced thermal states (DTSs) evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g . The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.

Chinese Physics B•Dec 1, 2017•8 citations

Entropy evolution law of a general linear state for diffusion noise

Yingyu Zhang, Yixing Wang

Abstract Based on the Kraus operator-sum representation of the analytical solution of the diffusion equation, we obtain the evolution of a general linear state in the diffusion channel. Also, we study the quantum statistical properties of the initial general linear state and its von-Neumann entropy evolution in the diffusion channel, especially find that the entropy evolution is influenced by the diffusion noise and the thermal parameter but without the displacement.

Chinese Physics B•May 7, 2025•1 citation

Decoherence and evolution of a general quadratic state for amplitude decay

Zhi-Long Wan, Hong-Chun Yuan, Xiangyu Yin +1 more

Abstract Making full use of the operator ordering method and the integration within ordered products, we obtain the analytical evolution law of a general quadratic state in the amplitude decay channel, and find that it is determined not only by the decay rate of the amplitude decay channel but also by the coefficients of the initial quadratic state. Further, the quantum statistical properties of the initial quadratic state for amplitude decay are investigated via its average photon number and photon-counting distribution, and its Wigner distribution function evolution is discussed in detail.

Chinese Physics B•Jul 3, 2025•0 citations

Time evolution of entropy variation for coherent state in quantum diffusion channel

Zhi-Long Wan, Hong-Yi Fan, Xiao-Lei Yin +1 more

In quantum statistics theory, very few systems’ quantum entropy can be evaluated, since the quantum entropy’s formula by von-Neumann is [Formula: see text] where [Formula: see text] is density operator, [Formula: see text] is the Boltzmann constant, and the natural logarithm [Formula: see text] is quite difficult to treat. In this work, we tackle how to derive the entropy evolution of an initial coherent state undergoing a quantum diffusion process. We employ the method of integration within ordered product (IWOP) of operators to derive the final mixed state, which is a displaced chaotic state, and then deduce its entropy.

Modern Physics Letters A•Oct 30, 2025•0 citations

Evolution of the photon-added coherent state in a laser channel

Jun Zhou, Jun Song, Hao Yuan +1 more

We investigate the time evolution of a quantum state in the laser channel with cavity gain coefficient g and loss coefficient κ by virtue of the thermo entangled state representation. This is a new approach for solving master equations. We exactly calculate the evolving result of the photon-added coherent state (PACS) governed by the master equation describing the laser process, and the normal ordered form of the density operator in the laser channel is derived, based on which we calculate the Wigner function analytically and graphically. The corresponding law of the PACS evolution in the laser channel is evaluated.

Canadian Journal of Physics•Jun 1, 2012•1 citation

Evolution law of Wigner function in laser process

Rui He, Junhua Chen, Hong-Yi Fan

Based on the density operator’s operator-sum representation recently obtained by Fan and Hu for a laser process (Opt. Commun., 2008, 281: 5571; Opt. Commun., 2009, 282: 932; Phys. Lett. B, 2008, 22: 2435), we derive the evolution law of Wigner operator, the law is concisely expressed in the normally ordered form $\Delta (\alpha ,\alpha ^* ,t) = \tfrac{T} {\pi }:\exp [ - 2T(a^\dag e^{ - (\kappa - g)t} - \alpha ^* )(ae^{ - (\kappa - g)t} - \alpha )] $ :, where g and κ are the cavity gain and the loss, respectively, and T ≡ (κ − g)(κ + g − 2ge−2(κ−g)t )−1:, When $t = 0,\Delta (\alpha ,\alpha ^* ,t) \to \tfrac{1} {\pi }:\exp [ - 2(a^\dag - \alpha ^* )(a - \alpha )] $ ;, which is the initial Wigner operator. Using this formalism the evolution law of Wigner functions in laser process can be directly obtained.

Frontiers of Physics•May 4, 2013•4 citations
Using the integration within ordered products, we obtain the analytical density-operator evolution of the general quadratic state ρ 0 in a laser channel, which always maintains the same form as the initial density operator ρ 0. Introducing the differential representation of the von-Neumann entropy and two important resemble formulas, we analytically and numerically investigate the entropy evolution of the state ρ 0 in a laser channel, which is determined by not only the competition of the gain and loss of the laser channel, but also the coefficients α, β of the initial quadratic state ρ 0.
We investigate how displaced thermal states (DTSs) evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g . The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.
Abstract Making full use of the operator ordering method and the integration within ordered products, we obtain the analytical evolution law of a general quadratic state in the amplitude decay channel, and find that it is determined not only by the decay rate of the amplitude decay channel but also by the coefficients of the initial quadratic state. Further, the quantum statistical properties of the initial quadratic state for amplitude decay are investigated via its average photon number and photon-counting distribution, and its Wigner distribution function evolution is discussed in detail.
In quantum statistics theory, very few systems’ quantum entropy can be evaluated, since the quantum entropy’s formula by von-Neumann is [Formula: see text] where [Formula: see text] is density operator, [Formula: see text] is the Boltzmann constant, and the natural logarithm [Formula: see text] is quite difficult to treat. In this work, we tackle how to derive the entropy evolution of an initial coherent state undergoing a quantum diffusion process. We employ the method of integration within ordered product (IWOP) of operators to derive the final mixed state, which is a displaced chaotic state, and then deduce its entropy.
We investigate the time evolution of a quantum state in the laser channel with cavity gain coefficient g and loss coefficient κ by virtue of the thermo entangled state representation. This is a new approach for solving master equations. We exactly calculate the evolving result of the photon-added coherent state (PACS) governed by the master equation describing the laser process, and the normal ordered form of the density operator in the laser channel is derived, based on which we calculate the Wigner function analytically and graphically. The corresponding law of the PACS evolution in the laser channel is evaluated.
Based on the density operator’s operator-sum representation recently obtained by Fan and Hu for a laser process (Opt. Commun., 2008, 281: 5571; Opt. Commun., 2009, 282: 932; Phys. Lett. B, 2008, 22: 2435), we derive the evolution law of Wigner operator, the law is concisely expressed in the normally ordered form $\Delta (\alpha ,\alpha ^* ,t) = \tfrac{T} {\pi }:\exp [ - 2T(a^\dag e^{ - (\kappa - g)t} - \alpha ^* )(ae^{ - (\kappa - g)t} - \alpha )] $ :, where g and κ are the cavity gain and the loss, respectively, and T ≡ (κ − g)(κ + g − 2ge−2(κ−g)t )−1:, When $t = 0,\Delta (\alpha ,\alpha ^* ,t) \to \tfrac{1} {\pi }:\exp [ - 2(a^\dag - \alpha ^* )(a - \alpha )] $ ;, which is the initial Wigner operator. Using this formalism the evolution law of Wigner functions in laser process can be directly obtained.