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Physica Scripta

Enhanced quantum features of non-Gaussian states by applying a two-mode squeezing operator to two generalized single-mode squeezed vacuum states

Truong Minh Duc, Dinh Phuoc Le, Tran Quang Dat, Anh Hien Thi Phan

Published Nov 1, 2025• 2 citations
Publisher

Abstract

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.

DOI
10.1088/1402-4896/ae1fb7

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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.
Abstract Recently, photon subtraction from the single-mode squeezed vacuum state (SVS) has been explored as a technique to enhance its squeezing strength (SS). Notably, the enhancement is observed only when an even number of photons is subtracted, and this effect is limited to a specific range of the squeezing parameter r. In this paper, we introduce a novel class of single-mode nonclassical states, termed as qubit superposed SVSs (qSSVSs), via the coherent superposition of a SVS and a single-photon-subtracted SVS. The primary objective of this work is to enhance the SS for any r > 0 through the creation of these superposed states. Our analysis reveals that the qSSVSs not only improve the SS but also exhibit enhanced nonclassical features such as the negativity of Wigner function, single-mode antibunching effect, photon-number distribution, and sub-Poissonian photon statistics. Furthermore, we demonstrate that the qSSVSs provide superior phase sensitivity in a quantum Mach–Zehnder interferometer compared to the original SVS. Importantly, the generation of qSSVSs is feasible using readily available optical devices, including a beam splitter, a photodetector, and an amplitude displacement. These states hold significant potential for practical applications in quantum information science, particularly for tasks such as information encoding and processing in quantum computing systems.
We investigate the phase sensitivity of a Mach-Zehnder Interferometer (MZI) with an input of a non-Gaussian quantum entangled state, Two-Mode Photon-Subtracted Squeezed Vacuum states (TMPSSV). Parity detection is carried out at the output of the interferometer to obtain the phase uncertainty, which is a physical parameter that can quantify the sensitivity of interferometry. According to the simulation results, TMPSSV has a smaller phase uncertainty than the Two-Mode Squeezed Vacuum state (TMSV) in the entire range of the squeezing parameter which means the sensitivity of interferometry based on TMPSSV is higher than that of TMSV. Therefore, non-Gaussian entanglement based on TMPSSV provides a promising quantum resource for an ultra-sensitivity optical interferometer far beyond the standard quantum limit.
Abstract A class of non-Gaussian entangled states is introduced by applying the nonlocal single-photon addition to two-mode squeezed vacuum state and the properties of entanglement are numerically investigated according to linear entropy and Einstein–Podolsky–Rosen (EPR) steering. After the nonlocal single-photon addition operation, Wigner function of the generated state appears some negative region and loses its Gaussian property in phase space. In essence, non-Gaussian entangled states are generated after applying nonlocal single-photon addition. Additionally, by studying the linear entropy and EPR steering, we find that single-photon addition can enhance their entanglement degree and non-Gaussian steering can be witnessed in a large range of squeezing parameter for the second-order quadratures, which may provide a well application in the fields of quantum information processing.
Quantum metrology aims to achieve measurement precision that surpasses classical limits in the estimation of physical parameters. In realistic conditions, however, its advantage can be diminished by interactions between a quantum system and its environment. This necessitates careful design of quantum resources that can sustain enhanced performance even under noise. Here, we investigate how a quantum non-Gaussian operation can provide an advantage in noisy quantum metrology. Specifically, we examine the effect of single-photon subtraction applied to a two-mode squeezed vacuum state in the task of phase estimation using a Mach–Zehnder interferometer under photon loss. The single-photon subtraction can be implemented either before or after the first beam splitter in the interferometer. By evaluating the quantum Fisher information for both the original and the photon-subtracted states, we assess the potential enhancement in sensing precision. We show that the enhancement occurs when photon subtraction is performed before the first beam splitter, provided that loss acts only on the signal mode. Our findings shed light on the role of non-Gaussian operations in noisy quantum metrology, clarifying when photon subtraction can yield a genuine advantage over Gaussian resources.
We theoretically explore the advantages rendered by non-Gaussian operations in phase estimation using a parity-detection-based Mach-Zehnder interferometer, with one input being a coherent state and the other being a non-Gaussian squeezed vacuum state (SVS). We consider a realistic model to perform three different non-Gaussian operations, namely, photon subtraction, photon addition, and photon catalysis on a single-mode SVS. We start by deriving the Wigner function of the non-Gaussian SVSs, which is then utilized to derive the expression for the phase sensitivity. The analysis of the phase sensitivity reveals that all three different non-Gaussian operations can enhance the phase sensitivity under suitable choices of parameters. We also consider the probabilistic nature of these non-Gaussian operations, the results of which reveal the single-photon addition to be the optimal operation. Further, our analysis also enables us to identify the optimal squeezing of the SVS and the transmissivity of the beam splitter involved in the implementation of the non-Gaussian operations.
We theoretically analyze phase sensitivity using a parity-detection-based Mach-Zehnder interferometer (MZI) with the input states generated by performing non-Gaussian operations, viz., photon subtraction, photon addition, and photon catalysis, on a two-mode squeezed vacuum (TMSV) state. Since these non-Gaussian operations are probabilistic, it is of utmost importance to take the success probability into account. To this end, we consider a realistic model of photon subtraction, addition, and catalysis and derive a single expression of the Wigner function for photon subtracted, added, and catalyzed TMSV states. The Wigner function is used to evaluate the lower bound on the phase sensitivity via quantum Cram\'er-Rao bound and parity-detection-based phase sensitivity in the MZI. We identify the ranges of squeezing and transmissivity parameters where the non-Gaussian states provide better phase sensitivity than the TMSV state. Taking the success probability into account, it turns out that the photon addition is the most advantageous among all three non-Gaussian operations. We hope that the generalized Wigner function derived in this paper will be useful in various quantum information protocols and state characterization.