arXiv subjects

Xue-feng Zhan

Publications and source records attributed to Xue-feng Zhan.

6 recordsLinked to original sources

arXiv2026

Information Geometry of Four-Parameter Single-Qutrit States: From Quantum to Semiclassical Geometric Tensors

The gap between the classical and quantum Fisher information matrices (CFIM and QFIM) separates what is operationally accessible through measurements from what is intrinsic to a quantum state. In the multiparameter setting, this quantum obstruction is generically not saturable. Motivated by the recently introduced semiclassical geometric tensor (SCGT), we perform an explicit information-geometric study for a class of pure four-parameter single-qutrit states (FPSQSs). These states are probed by a one-parameter family of measurements that interpolates between an uninformative POVM and a sharp projective measurement. We derive closed-form expressions for the CFIM, the quantum geometric tensor (QGT), and the SCGT. We show that the SCGT reproduces the QGT in the projective limit and vanishes in the trivial limit. The real part of the SCGT splits into two terms: the CFIM and an additional nonnegative measurement-transmitted metric in the phase sector. Its imaginary part provides a semiclassical Berry curvature. Its loss relative to the QGT is quantified by a measurement-dependent gap. Our results provide an exactly solvable four-parameter platform for the semiclassical geometric framework. They also clarify how realistic measurements read out the geometric content of quantum states, and how they partially degrade it.

quant-ph↗

arXiv2025

Exploring entanglement, Wigner negativity and Bell nonlocality for anisotropic two-qutrit states

We introduce a family of anisotropic two-qutrit states (AITTSs). These AITTSs are expressed as $ρ_{aiso}=p\left\vert ψ_{\left( θ,ϕ\right) }\right\rangle \left\langle ψ_{\left( θ,ϕ\right)}\right\vert +(1-p)\frac{1_{9}}{9}$ with $\left\vert ψ_{\left( θ,ϕ\right) }\right\rangle =\sin θ\cos ϕ\left\vert00\right\rangle +\sin θ\sin ϕ\left\vert 11\right\rangle +\cosθ\left\vert 22\right\rangle $ and $1_{9}=\sum_{j,k=0}^{2}\left\vert jk\right\rangle \left\langle jk\right\vert $. For a given $p\in \lbrack 0,1]$, these states are adjustable in different ($θ,ϕ$) directions. In the case of ($θ,ϕ$) = ($\arccos (1/\sqrt{3}),π/4$), the AITTS will reduce to the isotropic two-qutrit state $ρ_{iso}$. In addition, the AITTSs are severely affected by the white noise ($ρ_{noise}=1_{9}/9$). Three properties of the AITTSs, including entanglement, Wigner negativity and Bell nonlocality, are explored detailedly in the analytical and numerical ways. Each property is witnessed by an appropriate existing criterion. Some of our results are summarized as follows: (i) Large entanglement does not necessarily mean high Wigner negativity and strong Bell nonlocality. (ii) A pure state with a large Schmidt number does not necessarily have a greater Wigner negativity. (iii) Only when $\left\vertψ_{\left( θ,ϕ\right) }\right\rangle $ has the Schmidt number 3, the AITTS has the possibility of exhibiting Bell nonlocality in proper parameter range.

quant-ph↗

arXiv2024

Tripartite entanglement and tripartite steering in three-qubit pure states induced by vacuum--one-photon superpositions

Utilizing a tritter with variable parameter $T$ and induced by vacuum--one-photon superpositions $\left\vert 0\right\rangle +α\left\vert 1\right\rangle $ with $α=\left\vert α\right\vert e^{iϕ}$, we propose a scheme to prepare a class of three-qubit pure states. These states take the form of $\left\vert ψ\right\rangle _{123}=c_{0}\left\vert 000\right\rangle +c_{1}\left\vert 100\right\rangle +c_{2}\left\vert 010\right\rangle +c_{3}\left\vert 001\right\rangle $. The coefficients ($c_{0}$, $c_{1}$, $c_{2}$, and $c_{3}$) can be manipulated through interaction parameters ($\left\vert α\right\vert $, $ϕ$, and $T$). In line with Xie and Eberly's work[Phys. Rev. Lett. 127, 040403 (2021)], we investigate the genuine tripartite entanglement for $\left\vert ψ\right\rangle _{123}$ by using the measure of concurrence fill. Drawing on Hao \textit{et al.}'s research [Phys. Rev. Lett. 128, 120402 (2021)], we examine tripartite steering for $\left\vert ψ\right\rangle _{123}$ under certain measurements based on the uncertainty relations criterion. We identify nine potential configurations exhibiting varying steerability across different parameter spaces. It is important to highlight that, while the state $\left\vert ψ\right\rangle _{123}$ exhibits entanglement, steering remains unattainable in a substantial portion of the parameter space.

quant-ph↗

arXiv2023

Noiselessly amplified thermal states and after multi-photon addition or subtraction

In this paper, we introduce a noiselessly amplified thermal state (ATS), by operating the noiseless amplification operator ($g^{\hat{n}}$) on the thermal state (TS) with corresponding mean photon number (MPN) $\bar{n}$. Actually, the ATS is an new TS with MPN $\bar{N}=g^{2}\bar{n}/[1-\bar{n}\left(g^{2}-1\right)]$. Furthermore, we introduce photon-added-ATS (PAATS) and photon-subtracted-ATS (PSATS) by operating $m$-photon addition ($\hat{a}^{†m}$) and $m$-photon subtraction ($\hat{a}^{m}$) on the ATS, respectively. We study photon number distributions (PNDs), purities, and Wigner functions (WFs) for all these states.

quant-ph↗

arXiv2022

Multiphoton states engineering by heralded interference via six-port Mach-Zehnder interferometer

Based on heralded interference on a six-port Mach-Zehnder interferometer, we propose protocols to generate a series of multiphoton states in primary output port, by injecting a coherent state in primary input port and two Fock states in two ancillary input ports, and measuring two Fock states in two ancillary output ports. Only manipulating at the single-photon level (i.e, |0> or |1>) in all ancillary ports, we generate sixteen types (six categories) of multiphoton nonclassical states, whose state vectors are unified as superposition of a new coherent state, a single-photon added coherent state, and a two-photon added coherent state. Indeed, a wide range of nonclassical phenomena can be created by modulating the interaction parameters (including coherent field strength and shift phase). We mainly analyze quadrature-squeezing effects for all our considered states. Of particular interest is maximum squeezing of up to 2.57dB, with success probability 6.7%, at least in our present cases.

quant-ph↗

arXiv2022

Multi-photon-addition amplified coherent state

State $g^{\hat{n}}\hat{a}^{†m}\left\vert α\right\rangle $ and state $\hat{a}^{†m}g^{\hat{n}}\left\vert α\right\rangle $ are same to state $\hat{a}^{†m}\left\vert gα\right\rangle $, which is called as multi-photon-addition amplified coherent state (MPAACS) by us. Here, $\hat{n}$, $\hat{a}^{†}$, $\left\vert α\right\rangle $, $g$ ( $\geq 1$), and $m$ are photon number operator, creation operator, coherent state, gain facor, and an interger, respectively. We study mathematical and physical properties for these MPAACSs, including normalization, photon component analysis, Wigner function, effective gain, quadrature squeezing, and equivalent input noise. Actually, the MPAACS, which contains more nonclassicality, is an amplified version of photon-added coherent state (PACS) introduced by Agrwal and Tara [Phys. Rev. A 43, 492 (1991)]. Our work provides theoretical references for implementing amplifiers for light fields.

quant-ph↗