© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:2212.14343 · Physical Review Research

Continuous-variable nonclassicality certification under coarse-grained measurement

Chan Roh, Young-Do Yoon, Jiyong Park, Young-Sik Ra

Published Oct 18, 2023• 11 citations

Abstract

Coarse graining is a common imperfection of realistic quantum measurement, obstructing the direct observation of quantum features. Under highly coarse-grained measurement, we experimentally certify the continuous-variable nonclassicality of both Gaussian and non-Gaussian states. Remarkably, we find that this coarse-grained measurement outperforms the conventional fine-grained measurement for nonclassicality certification: it detects nonclassicality beyond the reach of the variance criterion, and furthermore, it exhibits stronger statistical significance than the high-order moments method. Our work demonstrates the usefulness of coarse-grained measurement by providing a reliable and efficient way of nonclassicality certification for quantum technologies.

DOI: 10.1103/physrevresearch.5.043057

Related papers

Continuous-variable nonclassicality certification under coarse-grained measurement

Chan Roh, Young-Do Yoon, Jiyong Park +1 more

We experimentally certify the nonclassicality of continuous-variable quantum states under coarse-grained measurement. Furthermore, we show that the coarse-grained measurement generally outperforms the ideal fine-grained measurement in nonclassicality detection.

Quantum 2.0 Conference and Exhibition•Jan 1, 2024•0 citations

Quantum Metrology under Coarse-Grained Measurement

Byeong-Yoon Go, Geunhee Gwak, Young-Do Yoon +4 more

While quantum metrology enables measurement precision beyond classical limits, its performance is often susceptible to experimental imperfections. Most prior studies have focused on imperfections in quantum states and operations. Here, we investigate the effect of coarse graining in quantum measurement through both theoretical analysis and experimental demonstration. Using an interferometer with a squeezed vacuum and a laser input, we analyze how coarse graining in homodyne detection affects the precision of phase estimation. We evaluate the Fisher information under various coarse-graining conditions and determine, in each case, an optimal estimation strategy that saturates the Cramér-Rao bound. Remarkably, even extremely coarse-grained measurement -- with only two bins -- enables phase estimation beyond the standard quantum limit and even achieves a precision that follows the Heisenberg scaling. We experimentally demonstrate quantum-enhanced phase estimation under coarse-grained homodyne detection. To determine an optimal estimation strategy, we employ the method of moments and present calibration procedures that enable its application to general experimental settings. Using only two bins, we observe a quantum enhancement of 1.2 dB compared to the classical method using the ideal measurement, improving towards 3.8 dB as the bin number increases. These results highlight a practical pathway to achieving quantum enhancement under the presence of severe experimental imperfections.

quant-pharXiv:2601.16106•Optics Express•Jan 23, 2026•0 citations

Continuous-Variable Nonclassicality Detection under Coarse-Grained Measurement

Chan Roh, Young-Do Yoon, Jiyong Park +1 more

We experimentally detect the nonclassicality of continuous-variable quantum states under coarse-grained measurement. Furthermore, we show that the coarse-grained measurement generally outperforms the ideal fine-grained measurement in nonclassicality detection.

•Jan 1, 2023•0 citations

Verifying single-mode nonclassicality beyond negativity in phase space

Jiyong Park, Jaehak Lee, Hyunchul Nha

While negativity in phase space is a well-known signature of nonclassicality, a wide variety of nonclassical states require their characterization beyond negativity. We establish a framework of nonclassicality in phase space that addresses nonclassical states comprehensively with a direct experimental evidence. This includes the negativity of phase-space distribution as a special case and further analyzes quantum states with positive distributions effectively. We prove that it detects all nonclassical Gaussian states and all non-Gaussian states of arbitrary dimension remarkably by examining three phase-space points only. Our formalism also provides an experimentally accessible lower bound for a nonclassicality measure based on trace distance. Importantly, this foundational approach can be further adapted to constitute practical tests in two directions looking into particle and wave nature of bosonic systems, via an array of nonideal on-off detectors and coarse-grained homodyne measurement, respectively. All these tests are practically powerful in characterizing nonclasssical states reliably against noise, making a versatile tool for a broad range of quantum systems in quantum technologies.

arXiv:2005.05739•Physical Review Research•Nov 15, 2021•11 citations

Reliable Entanglement Detection under Coarse-Grained Measurements

D. S. Tasca, Łukasz Rudnicki, Rafael M. Gomes +2 more

We derive reliable entanglement witnesses for coarse-grained measurements on continuous variable systems. These witnesses never return a "false positive" for identification of entanglement, under any degree of coarse graining. We show that even in the case of Gaussian states, entanglement witnesses based on the Shannon entropy can outperform those based on variances. We apply our results to experimental identification of spatial entanglement of photon pairs.

arXiv:1210.5945•Physical Review Letters•May 1, 2013•44 citations

Reliable Entanglement Detection Under Coarse-Grained Measurements

Stephen Patrick Walborn, Łukasz Rudnicki, D. S. Tasca +2 more

We derive reliable entanglement witnesses for coarse-grained measurements on continuous variable systems. These witnesses never return a ``false positive" for identification of entanglement, under any degree of coarse graining. We show that, even in the case of Gaussian states, entanglement witnesses based on the Shannon entropy can outperform those based on variances. We apply our results to experimental identification of spatial entanglement of photon pairs.

The Rochester Conferences on Coherence and Quantum Optics and the Quantum Information and Measurement meeting•Jan 1, 2013•3 citations

Coarse graining is a common imperfection of realistic quantum measurement, obstructing the direct observation of quantum features. Under highly coarse-grained measurement, we experimentally certify the continuous-variable nonclassicality of both Gaussian and non-Gaussian states. Remarkably, we find that this coarse-grained measurement outperforms the conventional fine-grained measurement for nonclassicality certification: it detects nonclassicality beyond the reach of the variance criterion, and furthermore, it exhibits stronger statistical significance than the high-order moments method. Our work demonstrates the usefulness of coarse-grained measurement by providing a reliable and efficient way of nonclassicality certification for quantum technologies.

While quantum metrology enables measurement precision beyond classical limits, its performance is often susceptible to experimental imperfections. Most prior studies have focused on imperfections in quantum states and operations. Here, we investigate the effect of coarse graining in quantum measurement through both theoretical analysis and experimental demonstration. Using an interferometer with a squeezed vacuum and a laser input, we analyze how coarse graining in homodyne detection affects the precision of phase estimation. We evaluate the Fisher information under various coarse-graining conditions and determine, in each case, an optimal estimation strategy that saturates the Cramér-Rao bound. Remarkably, even extremely coarse-grained measurement -- with only two bins -- enables phase estimation beyond the standard quantum limit and even achieves a precision that follows the Heisenberg scaling. We experimentally demonstrate quantum-enhanced phase estimation under coarse-grained homodyne detection. To determine an optimal estimation strategy, we employ the method of moments and present calibration procedures that enable its application to general experimental settings. Using only two bins, we observe a quantum enhancement of 1.2 dB compared to the classical method using the ideal measurement, improving towards 3.8 dB as the bin number increases. These results highlight a practical pathway to achieving quantum enhancement under the presence of severe experimental imperfections.

While negativity in phase space is a well-known signature of nonclassicality, a wide variety of nonclassical states require their characterization beyond negativity. We establish a framework of nonclassicality in phase space that addresses nonclassical states comprehensively with a direct experimental evidence. This includes the negativity of phase-space distribution as a special case and further analyzes quantum states with positive distributions effectively. We prove that it detects all nonclassical Gaussian states and all non-Gaussian states of arbitrary dimension remarkably by examining three phase-space points only. Our formalism also provides an experimentally accessible lower bound for a nonclassicality measure based on trace distance. Importantly, this foundational approach can be further adapted to constitute practical tests in two directions looking into particle and wave nature of bosonic systems, via an array of nonideal on-off detectors and coarse-grained homodyne measurement, respectively. All these tests are practically powerful in characterizing nonclasssical states reliably against noise, making a versatile tool for a broad range of quantum systems in quantum technologies.