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Modern Physics Letters A

Analytical construction of two-mode squeezed vacuum states with two tunable parameters

Gang Ren, Hai-jun Yu, Chunzao Zhang

Published May 8, 2025• 1 citation
Publisher

Abstract

We theoretically construct a two-parameter two-mode squeezing operator by combining the two-mode coupled harmonic oscillator Hamiltonian with beam splitter transformations. A novel two-mode squeezed vacuum state (NTMSVS) is generated via the application of this operator to the two-mode vacuum state. Numerical investigations demonstrate that the NTMSVS exhibits intermediate properties between the conventional two-mode squeezed vacuum state (TMSVS) and the product state of two independent single-mode squeezed vacua across multiple quantum metrics, including Wigner distribution characteristics, logarithmic negativity, EPR steering robustness and Bell inequality violation. Notably, the quadrature squeezing and sum squeezing amplitudes are significantly amplified under specific parametric regimes, offering enhanced nonclassicality compared to standard squeezed states.

DOI
10.1142/s0217732325500671

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We theoretically construct a two-parameter two-mode squeezing operator by combining the two-mode coupled harmonic oscillator Hamiltonian with beam splitter transformations. A novel two-mode squeezed vacuum state (NTMSVS) is generated via the application of this operator to the two-mode vacuum state. Numerical investigations demonstrate that the NTMSVS exhibits intermediate properties between the conventional two-mode squeezed vacuum state (TMSVS) and the product state of two independent single-mode squeezed vacua across multiple quantum metrics, including Wigner distribution characteristics, logarithmic negativity, EPR steering robustness and Bell inequality violation. Notably, the quadrature squeezing and sum squeezing amplitudes are significantly amplified under specific parametric regimes, offering enhanced nonclassicality compared to standard squeezed states.
Abstract This paper investigates the quantum features of non-Gaussian states generated by applying a two-mode squeezing operator S ˆ a b ( s ) to two generalized single-mode squeezed vacuum states (SVSs), each formed by the superposition of an SVS and a single–photon–subtracted SVS. The results show that, in the new states, the two-mode squeezing effect, the Einstein–Podolsky–Rosen (EPR) correlation, the Hillery–Zubairy entanglement, and the linear entropy are all enhanced as the two-mode squeezing parameter s increases. Moreover, both the degrees of squeezing and entanglement are improved and exceed those of the two-mode squeezed vacuum state (TMSVS) for stronger single-mode squeezing parameters. The optimal conditions for achieving such enhancements are identified for different regimes, depending on whether the generalized SVSs are purely Gaussian, maximally non-Gaussian, or intermediate states. In an application, the quantum Cramér–Rao bound (QCRB) is evaluated when the non-Gaussian states are employed as inputs to a Mach–Zehnder interferometer (MZI). The results further demonstrate that the enhanced phase sensitivity in the MZI originates from both the squeezing strengths and the intrinsic photon-subtraction operation. These findings highlight the potential of the new non-Gaussian states as promising resources for quantum metrology and quantum sensing.
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We investigate the statistical and quadrature squeezings, as well as the entanglement properties, of a two-mode light generated by non-degenerate parametric oscillations coupled to a two-mode squeezed vacuum reservoir, by employing the solutions of the quantum Langevin equations. It is found that the two-mode light shows the two-mode squeezing and entanglement for all values of the time. Moreover, it is observed that the squeezed vacuum reservoir and the growing amplitude of the pump mode enhance the degrees of two-mode squeezing and entanglement. We have also shown that the amounts of squeezing and entanglement are significant in a region, where the mean photon number is higher, and the photon number correlation is lower.
Abstract In this work, we present a theoretical scheme for generating a new kind of tunable non-Gaussian entangled state, by means of beam splitters and multi-photon conditional measurement with two-mode squeezed vacuum state (TMSVS) inputs. The output state is proven to be two-variable Hermite polynomial excited squeezed vacuum states, whose success probability of detection relates to the Jacobi polynomials. We then mainly study the entanglement properties of the output state for the symmetric case quantified by the von Neumann entropy and Einstein–Podolsky–Rosen correlation. It is shown that the entropy of entanglement is valid for verifying the improvement of entanglement within a certain range of squeezing parameter and transmissivity, and the resulting state case may possess a stronger correlation than the initial TMSVS by increasing the transmissivity or photon number of detection. In addition, the violation of the Clauser–Horne–Shimony–Holt (CHSH) inequality for the output state is also evaluated in terms of Wigner representation in phase space. It is found that the negative region of Wigner function distribution becomes more visible with the increase of the photon number of detection, and the degree of the violation of the CHSH inequality significantly increases as the photon number of detection for the symmetrical case increases. The resulting state with highly nonclassical characteristics will provide a useful application in the fields of quantum information processing.