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1. On the equivalence between squeezing and entanglement potential for two-mode Gaussian states

   https://doi.org/10.1038/s41598-023-38572-1  

   Li, Bohan; Das, Aritra; Tserkis, Spyros; Narang, Prineha; Lam, Ping Koy; Assad, Syed M. (December 2023, Scientific Reports)

   Abstract The maximum amount of entanglement achievable under passive transformations by continuous-variable states is called the entanglement potential. Recent work has demonstrated that the entanglement potential is upper-bounded by a simple function of the squeezing of formation, and that certain classes of two-mode Gaussian states can indeed saturate this bound, though saturability in the general case remains an open problem. In this study, we introduce a larger class of states that we prove saturates the bound, and we conjecture that all two-mode Gaussian states can be passively transformed into this class, meaning that for all two-mode Gaussian states, entanglement potential is equivalent to squeezing of formation. We provide an explicit algorithm for the passive transformations and perform extensive numerical testing of our claim, which seeks to unite the resource theories of two characteristic quantum properties of continuous-variable systems. 

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2. The power of microscopic nonclassical states to amplify the precision of macroscopic optical metrology

   https://doi.org/10.1038/s41534-022-00670-9  

   Ge, Wenchao; Jacobs, Kurt; Zubairy, M. Suhail (December 2023, npj Quantum Information)

   Abstract It is well-known that the precision of a phase measurement with a Mach-Zehnder interferometer employing strong classic light can be greatly enhanced with the addition of weak nonclassical light. In the context of quantifying nonclassicality, the amount by which a nonclassical state can enhance precision in this way has been termed its ’metrological power’. To-date, the enhancement provided by weak nonclassical states has been calculated only for specific measurement configurations. Here we are able to optimize over all measurement configurations to obtain the maximum enhancement that can be achieved by any single or multi-mode nonclassical state together with strong classical states, for local and distributed quantum metrology employing any linear or nonlinear single-mode unitary transformation. Our analysis reveals that the quantum Fisher information for quadrature-displacement sensing is the sole property that determines the maximum achievable enhancement in all of these different scenarios, providing a unified quantification of the metrological power. 

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3. Mapping continuous-variable quantum states onto optical scalar beams

   https://doi.org/10.1088/2515-7647/ae2fa4  

   Rodríguez-Lara, B M; Becerra, F E (January 2026, Journal of Physics: Photonics)

   Abstract Optical scalar beams provide a platform to explore classical analogies to quantum mechanics. We introduce a Lie group-theoretic $\mathrm{su}(1,1)$framework to construct optical beam analogs of continuous-variable (CV) quantum states, including one- and two-mode squeezing. Using Fourier methods and the optical Wigner distribution, we investigate how squeezing reshapes the spatial and spectral structure of these beams, and find that the achievable diffraction-limited spatial compression is bounded by the numerical aperture of the optical system. We construct an optical analog of the Duan–Simon inseparability criterion and use marginal optical Wigner distributions, which encode partial phase-space information, as witnesses of CV classical entanglement. Our framework provides a unified approach to quantum-inspired beam engineering with potential applications in optical imaging, metrology, and communication. 

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4. Average Rényi entanglement entropy in Gaussian boson sampling

   https://doi.org/10.1103/PhysRevResearch.7.023125  

   Youm, Jason; Iosue, Joseph T; Ehrenberg, Adam; Wang, Yu-Xin; Gorshkov, Alexey V (May 2025, Physical review research)

   Recently, many experiments have been conducted with the goal of demonstrating a quantum advantage over classical computation. One popular framework for these experiments is Gaussian boson sampling, where quadratic photonic input states are interfered via a linear optical unitary and subsequently measured in the Fock basis. In this paper, we study the modal entanglement of the output states in this framework just before the measurement stage. Specifically, we compute Page curves as measured by various Rényi- $\alpha$entropies, where the Page curve describes the entanglement between two partitioned groups of output modes averaged over all linear optical unitaries. We derive these formulas for $\alpha =1$(i.e., the von Neumann entropy) and, more generally, for all positive integer $\alpha$, in the asymptotic limit of infinite number of modes and for input states that are composed of single-mode-squeezed-vacuum state with equal squeezing strength. We then analyze the limiting behaviors when the squeezing is small and large. Having determined the averages, we then explicitly calculate the Rényi- $\alpha$variance for integers $\alpha >1$and are able to show that these entropies are weakly typical. Published by the American Physical Society2025 

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5. Steganographic entanglement sharing

   https://doi.org/10.1103/kxpv-46v3  

   Avritzer, Bruno; Brun, Todd A (August 2025, Physical Review A)

   In a previous work [Avritzer and Brun, Phys. Rev. A 109, 032401 (2024)] we discussed a theoretical grounding for classical steganography using quantum Fock and coherent states in an optical channel, building on previous work by Wu et al. [Opt. Express 14, 3738 (2006); Opt. Express 21, 2065 (2013)]. In that work, we discussed protocols that disguise communications to mimic the thermal state of a harmonic oscillator. In this work we extend this to transmission of quantum information and demonstrate the utility of steganographic entanglement sharing in practical contexts like nonclassical state teleportation. We show that non-Gaussian entangled resources can be transmitted covertly while mimicking a Gaussian thermal state and still retain sufficient entanglement to violate a qubit Bell inequality, even with an eavesdropper present. We also examine the performance of other quantum protocols that utilize entanglement, such as dense coding and teleportation of unentangled but nonclassical states, to determine the effectiveness of the steganographic entanglement sharing under a variety of active and passive eavesdropper conditions. 

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