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Physical Review A

Enhancement of nonclassical properties of the two-mode squeezed vacuum state with a postselected von Neumann measurement

Janarbek Yuanbek, Yi-Fang Ren, Ahmad Abliz, Yusuf Turek

Published Nov 19, 2024• 7 citations
Publisher

Abstract

We investigate the effects of weak value amplification on the nonclassical properties of the two-mode squeezed vacuum state. We calculate the quadrature squeezing and second-order cross-correlation functions to demonstrate the advantages of postselective weak measurement (WM). We also examine the entanglement between the two modes by evaluating various entanglement criteria, including the Cauchy-Schwartz inequality, Hillery-Zubairy correlation, and Einstein-Podolsky-Rosen correlations. Our results show that postselected von Neumann measurements significantly optimize the two-mode squeezed vacuum state. Notably, the amplification effect of weak values plays a critical role in this process. We demonstrated that in the WM regime, as the weak values increase, the nonclassical properties of the two-mode squeezed vacuum state such as entanglement and correlations between the two modes become more pronounced compared to the original state. We also propose possible implementation methods for our approach using trapped ion systems and optical platforms. Our enhanced two-mode squeezed vacuum state may have potential applications in quantum information processing scenarios, such as single-photon generation, advanced imaging techniques, quantum computation, and long-distance quantum communication.

DOI
10.1103/physreva.110.052611

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We investigate the effects of weak value amplification on the nonclassical properties of the two-mode squeezed vacuum state. We calculate the quadrature squeezing and second-order cross-correlation functions to demonstrate the advantages of postselective weak measurement (WM). We also examine the entanglement between the two modes by evaluating various entanglement criteria, including the Cauchy-Schwartz inequality, Hillery-Zubairy correlation, and Einstein-Podolsky-Rosen correlations. Our results show that postselected von Neumann measurements significantly optimize the two-mode squeezed vacuum state. Notably, the amplification effect of weak values plays a critical role in this process. We demonstrated that in the WM regime, as the weak values increase, the nonclassical properties of the two-mode squeezed vacuum state such as entanglement and correlations between the two modes become more pronounced compared to the original state. We also propose possible implementation methods for our approach using trapped ion systems and optical platforms. Our enhanced two-mode squeezed vacuum state may have potential applications in quantum information processing scenarios, such as single-photon generation, advanced imaging techniques, quantum computation, and long-distance quantum communication.
Postselected von Neumann measurement characterized by postselection and weak value has been found to possess potential applications in quantum metrology and solved plenty of fundamental problems in quantum theory. As an application of this new measurement technique in quantum optics and quantum information processing, its effects on the features of single-mode radiation fields such as coherent state, squeezed vacuum state and Schrödinger cat sate are investigated by considering full-order effects of unitary evolution. The results show that the conditional probabilities of finding photons, second-order correlation functions, Qm -factors and squeezing effects of those states after the postselected measurement is significantly changed are comparable with the corresponding initial pointer states.
We investigate the effects of postselected von Neumann measurements on the nonclassical properties of pair coherent states (PCS). We calculated key quantum characteristics, such as squeezing, photon statistics, entanglement between the two modes of PCS, and teleportation fidelity. Our results demonstrate that postselected von Neumann measurements enhance both the non-Gaussianity and nonclassicality of PCS. These findings are validated by analyzing the scaled joint Wigner function across various system parameters. We also notice that in weak measurement regimes, the teleportation fidelity via a PCS-based quantum channel under postselected von Neumann measurements could maintain successful teleportation for anomalous weak values of the measured system observable. The theoretical optimization scheme offers an alternative approach for improving PCS-based quantum information efficiency and facilitates practical implementations in quantum technologies.
Abstract This paper mainly focuses on the optimization of the quantum Fisher information (QFI) for a single-photon subtracted squeezed vacuum (SPSSV) state within the framework of postselected von Neumann measurements. By utilizing the polarization and spatial degrees of freedom of the single-photon subtracted squeezed vacuum state as the measured system and the probe, respectively, the manipulation of the QFI is achieved via the probe state under standard postselected von Neumann measurement. The results demonstrate that a large QFI can invariably be obtained through the combinatory effects of the interaction strength and squeezing parameter, which characterizes the non-classical properties of the SPSSV state. The weak value is found to be crucial in increasing the QFI under weak interaction strength. Our findings clarify the weak-value amplification (WVA) effect on the QFI, thereby revealing the advantage of non-Gaussian states in information acquisition under postselected measurement. Meanwhile, this paper also presents the corresponding implementation scheme for optical experiments.
In quantum metrology, measurements are usually treated as passive readout processes. Here we investigate whether post-selected von Neumann measurements (PVNMs) can be used as an active resource to reshape the nonclassical properties of a two-mode entangled coherent state (ECS). By analyzing the finite-coupling post-selected state, we show that PVNMs can enhance quadrature squeezing and sum squeezing, increase the Wigner-function negativity, and strengthen bipartite correlations, as witnessed by the Hillery-Zubairy criterion and linear entropy. We further evaluate the quantum Fisher information and the corresponding quantum Cramér-Rao bound for phase estimation, and discuss the trade-off between metrological gain and measurement-induced disturbance through the fidelity. Our scheme exhibits a phase-sensitivity advantage over standard ECS metrology for large average photon numbers. Our results suggest that PVNMs provide a tunable route for engineering nonclassical resources in continuous-variable sensing protocols.
We investigate the effects of postselected von Neumann measurements on the nonclassical properties of pair coherent states (PCS). We calculated key quantum characteristics, such as squeezing, photon statistics, and entanglement between the two PCS modes. Our results demonstrate that postselected von Neumann measurements enhance both the non-Gaussianity and nonclassicality of PCS. These findings are validated by analyzing the scaled joint Wigner function across various system parameters. The theoretical optimization scheme offers an alternative approach for improving PCS-based quantum information efficiency and facilitates practical implementations in quantum technologies.