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

International Journal of Quantum Information

Effect of initial squeezing on tripartite continuous-variable entanglement of dynamical processes

Andri Pradana, Lock Yue Chew

Published Mar 30, 2022• 1 citation
Publisher

Abstract

In this paper, we investigate the effect of initial squeezing on tripartite continuous-variable (CV) Hamiltonians based on real physical systems. The Hamiltonians are based on the three-mode magnons excited by an external field, the one-dimensional interconnected tripartite spring-like system, and two spin ensembles coupled to a cavity resonator in the nondispersive regime in the CV limit. We find that for the three-mode magnons and the spring-like system, implementation of initial squeezing invariably enhances the two-way and three-way entanglement, while for the spin-resonator system, it depends on the alignment of the spin ensembles relative to the resonator field.

DOI
10.1142/s0219749922500083

Related papers

Entanglement of nitrogen-vacancy-center ensembles with initial squeezing

Andri Pradana, Lock Yue Chew

In this paper, we investigate entanglement of an experimental system of two nitrogen-vacancy-center ensembles which are initially squeezed under the one-axis twisting Hamiltonian. We take into account three scenarios in which initial squeezing and entanglement are mediated by phonons or photons: (a) the phonon-squeezed photon-entangled scenario, (b) the phonon-squeezed phonon-entangled scenario, and (c) the photon-squeezed photon-entangled scenario. For our investigation, we employ the Tavis-Cummings model, which includes dissipative decoherence of the collective spin ensemble, and analyze the system both for a relatively small number of spins and in the limit of a large number of spins using the approach of a quantum master equation. Although evidence in the literature on idealized coupled oscillator systems and coupled quantum kicked tops suggests that initial squeezing can enhance entanglement, we find that, in the realistic system studied in this paper, initial squeezing can improve entanglement overall when the field mode interacts in a particular manner with the two spin ensembles. Our analysis using the Holstein-Primakoff transformation and Wigner characteristic function in the rotating frame of reference shows that the entanglement enhancement is a subtle consequence of the way in which the dissipative decoherence rotates the state of the collective spin ensemble such that enhancement depends on the time-evolved rotated states between the presence and absence of initial squeezing.

Physical Review A•Aug 27, 2021•9 citations

Continuous–Variable Entanglement in a Coupled Field–Mesoscopic Josephson Junction System

Tian-Hai Zeng, Shao Bin, Chang Ping +1 more

Continuous–variable entanglement in the interacting system of a mesoscopic Josephson junction with a squeezed field is investigated. It is shown that when the cavity field is initially prepared in a squeezed vacuum state and the junction in its lowest energy state, the coupling system can evolve into a two-mode Gaussian state. The time-dependent characteristic function in the Wigner representation for the system is analytically obtained, and the squeezing degree of the initial cavity field turns out to have not only an apparent enhancing but also a weakening effect on the entanglement of the coupling system under suitable parameter conditions.

Chinese Physics Letters•Sep 27, 2006•6 citations

Enhanced entanglement via magnon squeezing in a two-cavity magnomechanical system

Amjad Sohail, Rizwan Ahmed, Jia‐Xin Peng +2 more

The present study is based on a theoretically feasible scheme for the enhancement of entanglement between different bipartitions due to magnon squeezing in a two-cavity magnomechanical system, having two microwave cavity mode photons, a magnon mode, and phonon mode. The nonlinearity in the system is well enhanced owing to magnon squeezing, which is responsible for the enhancement of different bipartitions’ entanglement. By employing the standard Langevin approach, we found that the magnon squeezing parameter not only enhances the entanglement between directly coupled modes, but also has a considerable impact on indirectly coupled modes’ entanglement. In addition, we find the negative impact of the thermal bath for the mechanical mode on the generation of photon–phonon and magnon–phonon entanglements. Furthermore, magnon squeezing has shown a significant role in the entanglement robustness against thermal effects. Moreover, the tripartite entanglement among photon, magnon, and phonon is also considerably enhanced in the presence of magnon squeezing. This two-cavity magnomechanical system might be used in quantum tasks that require the enhancement of entanglement of indirectly coupled modes.

Journal of the Optical Society of America B•Apr 3, 2023•60 citations

Squeezing of collective excitations in spin ensembles

Christian Kraglund Andersen, Klaus Mølmer

We analyze the possibility of creating two-mode spin squeezed states of two separate spin ensembles by inverting the spins in one ensemble and allowing spin exchange between the ensembles via a near resonant cavity field. We investigate the dynamics of the system using a combination of numerical and analytic calculations, and we obtain squeezing for a wide range of parameters. We also investigate the transfer of the squeezing properties to the cavity field and to an output mode from the cavity. Finally, we investigate how the squeezing is affected by effects of inhomogeneities which would be present in solid-state implementations of the spin ensembles.

arXiv:1207.6772•Physical Review A•Oct 22, 2012•8 citations

Threshold effect and entanglement enhancement through local squeezing of initial separable states in continuous-variable systems

Chen Er, Ning Ning Chung, Lock Yue Chew

We investigate the dynamical enhancement of entanglement by means of local squeezing of initial separable Gaussian states in two coupled harmonic oscillator systems. Interestingly, the maximum generation of entanglement between the two modes is not a monotonically increasing function of the squeezing parameter. Instead, there exists a critical degree of squeezing r c for the maximum entanglement to be enhanced. For the coupled oscillator systems considered, we have derived the analytical expressions of r c .

Physica Scripta•Jan 8, 2013•9 citations

Two-mode squeezing in a cold atomic ensemble

Arina Tashchilina

We investigate experimentally and theoretically the generation of a continuous variable entanglement using laser cooled atomic gas in free space and cavity mode. This is of a fundamental interest due to the nonclassical correlation of quadrature observables of the two-mode squeezed (TMS) state. The TMS state is the basis for complete quantum teleportation and continuous variable quantum repeaters. It is also used in quantum metrology and quantum key distribution. We employ a novel scheme for generating a TMS vacuum based on a non-degenerate four-wave mixing process in a cold atomic cloud coupled to a cavity. We send two pumps collinear to the cavity mode and ensure that the two generated quantum fields are simultaneously resonant with the cavity. The cavity enhancement enables us to demonstrate results close to a free space in hot atomic gases (-5.2 dB) where optical densities are much higher. Our system is versatile because, together with continuous variables, it is suitable for the discrete variable domain using the Duan-Lukin-Cirac-Zoller protocol. The design is oriented to make the delay between two modes possible and could be used for hybrid continuous repeaters. The system is devised and built fully as a part of my PhD, wherein we characterize our system and demonstrate the squeezing of -3.7 dB. Since the quantum dynamics of the system is not intuitive, we provide simple models and consolidate segmental information on generation of TMS states. To make sure that the dynamics is not oversimplified, we construct a novel theory where we treat both fields and atoms as quantum objects. The theory supports and enriches our understanding and confirms our experimental data. Based on the experimental and theoretical results we spotlight the detrimental effects and propose improvements to our system. We theoretically investigate that the certain class of TMSV states are optically dark. These states propagate through a polarized to one hyperfine level Λ atoms without degradation or evolution. Based on this we propose a new way of generation of TMSV through the dissipation or dynamically controlled broadening.

•Nov 1, 2019•1 citation
In this paper, we investigate the effect of initial squeezing on tripartite continuous-variable (CV) Hamiltonians based on real physical systems. The Hamiltonians are based on the three-mode magnons excited by an external field, the one-dimensional interconnected tripartite spring-like system, and two spin ensembles coupled to a cavity resonator in the nondispersive regime in the CV limit. We find that for the three-mode magnons and the spring-like system, implementation of initial squeezing invariably enhances the two-way and three-way entanglement, while for the spin-resonator system, it depends on the alignment of the spin ensembles relative to the resonator field.
In this paper, we investigate entanglement of an experimental system of two nitrogen-vacancy-center ensembles which are initially squeezed under the one-axis twisting Hamiltonian. We take into account three scenarios in which initial squeezing and entanglement are mediated by phonons or photons: (a) the phonon-squeezed photon-entangled scenario, (b) the phonon-squeezed phonon-entangled scenario, and (c) the photon-squeezed photon-entangled scenario. For our investigation, we employ the Tavis-Cummings model, which includes dissipative decoherence of the collective spin ensemble, and analyze the system both for a relatively small number of spins and in the limit of a large number of spins using the approach of a quantum master equation. Although evidence in the literature on idealized coupled oscillator systems and coupled quantum kicked tops suggests that initial squeezing can enhance entanglement, we find that, in the realistic system studied in this paper, initial squeezing can improve entanglement overall when the field mode interacts in a particular manner with the two spin ensembles. Our analysis using the Holstein-Primakoff transformation and Wigner characteristic function in the rotating frame of reference shows that the entanglement enhancement is a subtle consequence of the way in which the dissipative decoherence rotates the state of the collective spin ensemble such that enhancement depends on the time-evolved rotated states between the presence and absence of initial squeezing.
Continuous–variable entanglement in the interacting system of a mesoscopic Josephson junction with a squeezed field is investigated. It is shown that when the cavity field is initially prepared in a squeezed vacuum state and the junction in its lowest energy state, the coupling system can evolve into a two-mode Gaussian state. The time-dependent characteristic function in the Wigner representation for the system is analytically obtained, and the squeezing degree of the initial cavity field turns out to have not only an apparent enhancing but also a weakening effect on the entanglement of the coupling system under suitable parameter conditions.
The present study is based on a theoretically feasible scheme for the enhancement of entanglement between different bipartitions due to magnon squeezing in a two-cavity magnomechanical system, having two microwave cavity mode photons, a magnon mode, and phonon mode. The nonlinearity in the system is well enhanced owing to magnon squeezing, which is responsible for the enhancement of different bipartitions’ entanglement. By employing the standard Langevin approach, we found that the magnon squeezing parameter not only enhances the entanglement between directly coupled modes, but also has a considerable impact on indirectly coupled modes’ entanglement. In addition, we find the negative impact of the thermal bath for the mechanical mode on the generation of photon–phonon and magnon–phonon entanglements. Furthermore, magnon squeezing has shown a significant role in the entanglement robustness against thermal effects. Moreover, the tripartite entanglement among photon, magnon, and phonon is also considerably enhanced in the presence of magnon squeezing. This two-cavity magnomechanical system might be used in quantum tasks that require the enhancement of entanglement of indirectly coupled modes.
We analyze the possibility of creating two-mode spin squeezed states of two separate spin ensembles by inverting the spins in one ensemble and allowing spin exchange between the ensembles via a near resonant cavity field. We investigate the dynamics of the system using a combination of numerical and analytic calculations, and we obtain squeezing for a wide range of parameters. We also investigate the transfer of the squeezing properties to the cavity field and to an output mode from the cavity. Finally, we investigate how the squeezing is affected by effects of inhomogeneities which would be present in solid-state implementations of the spin ensembles.
We investigate the dynamical enhancement of entanglement by means of local squeezing of initial separable Gaussian states in two coupled harmonic oscillator systems. Interestingly, the maximum generation of entanglement between the two modes is not a monotonically increasing function of the squeezing parameter. Instead, there exists a critical degree of squeezing r c for the maximum entanglement to be enhanced. For the coupled oscillator systems considered, we have derived the analytical expressions of r c .
We investigate experimentally and theoretically the generation of a continuous variable entanglement using laser cooled atomic gas in free space and cavity mode. This is of a fundamental interest due to the nonclassical correlation of quadrature observables of the two-mode squeezed (TMS) state. The TMS state is the basis for complete quantum teleportation and continuous variable quantum repeaters. It is also used in quantum metrology and quantum key distribution. We employ a novel scheme for generating a TMS vacuum based on a non-degenerate four-wave mixing process in a cold atomic cloud coupled to a cavity. We send two pumps collinear to the cavity mode and ensure that the two generated quantum fields are simultaneously resonant with the cavity. The cavity enhancement enables us to demonstrate results close to a free space in hot atomic gases (-5.2 dB) where optical densities are much higher. Our system is versatile because, together with continuous variables, it is suitable for the discrete variable domain using the Duan-Lukin-Cirac-Zoller protocol. The design is oriented to make the delay between two modes possible and could be used for hybrid continuous repeaters. The system is devised and built fully as a part of my PhD, wherein we characterize our system and demonstrate the squeezing of -3.7 dB. Since the quantum dynamics of the system is not intuitive, we provide simple models and consolidate segmental information on generation of TMS states. To make sure that the dynamics is not oversimplified, we construct a novel theory where we treat both fields and atoms as quantum objects. The theory supports and enriches our understanding and confirms our experimental data. Based on the experimental and theoretical results we spotlight the detrimental effects and propose improvements to our system. We theoretically investigate that the certain class of TMSV states are optically dark. These states propagate through a polarized to one hyperfine level Λ atoms without degradation or evolution. Based on this we propose a new way of generation of TMSV through the dissipation or dynamically controlled broadening.