Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0702267 · Physical Review Letters

Measurement of Einstein-Podolsky-Rosen-Type Flavor Entanglement in Υ(4S)→B0B¯0 Decays

A. Go, A. Bay, K. Abe, H. Aihara, D. Anipko, K. F. Chen, T. Aushev, A. M. Bakich, E. L. Barberio, K. Belous, Urban Bitenc, Ilija Bizjak, S. Blyth, Andrzej Bozek, M. Bračko, Thomas E. Browder, P. Chang, Y. Chao, K. F. Chen, K. F. Chen, W. T. Chen, B. G. Cheon, R. Chistov, Y. Choi, Y. Choi, S. Cole, Jeremy Peter Dalseno, M. Danilov, M. Dash, A G Drutskoy, S. Eidelman, Denis A. Epifanov, S. Fratina, N. Gabyshev, T. Gershon, G. Gokhroo, B. Golob, A. Gorišek, H. Ha, Nicholas Craig HASTINGS, K. Hayasaka, Hisaki Hayashii, M. Hazumi, D. Heffernan, T. Hokuue, Y. Hoshi, Suen R. Hou, W.-S. Hou, Toru Iijima, Koji Ikado, A. Imoto, K. Inami, A. Ishikawa, H. Ishino, R. Itoh, M. Iwasaki, M. Iwasaki, C. Jacoby, J. H. Kang, Nobuhiko Katayama, T. Kawasaki, H. R. Khan, H. Kichimi, H. J. Kim, S. K. Kim, Y. J. Kim, K. Kinoshita, S. Korpar, P. Križan, P. Krokovny, R. Kulasiri, R. Kumar, C. C. Kuo, A. Kuzmin, Y. Kwon, Jens Sören Lange, M. J. Lee, M. J. Lee, T. Lesiak, A. Limosani, S.-W. Lin, Yang Liu, Dmitri Liventsev, T. Matsumoto, Adam Tomasz Matyja, S. McOnie, W. Mitaroff, H. Miyake, H. Miyata, Y. Miyazaki, R. Mizuk, T. Mori, E. Nakano, M. Nakao, Z. Natkaniec, Shohei Nishida, Osamu Nitoh, S. Ogawa, T. Ohshima, S. L. Olsen

Published Sep 26, 2007• 62 citations
arXivHTMLPDF

Abstract

The neutral B meson pair produced at the Upsilon(4S) should exhibit a nonlocal correlation of the type discussed by Einstein, Podolsky, and Rosen. We measure this correlation using the time-dependent flavor asymmetry of semileptonic B(0) decays, which we compare with predictions from quantum mechanics and two local realistic models. The data are consistent with quantum mechanics, and inconsistent with the other models. Assuming that some B pairs disentangle to produce B(0) and B(0) with definite flavor, we find a decoherent fraction of 0.029 +/ -0.057, consistent with no decoherence.

DOI
10.1103/physrevlett.99.131802

Related papers

Measurement of EPR-type flavour entanglement in U(4S) →

A. Bay

The neutral B-meson pair produced at the U(4S) should ex- hibit a non-local correlation of the type discussed by Einstein, Podol- ski, and Rosen. The time-dependent flavour asymmetry of the B mesons decaying into flavour eigenstates is used to test such a cor- relation. The asymmetry obtained from semileptonic B 0 decays is in agreement with the prediction from quantum mechanics and far away from the predictions of the local realistic models tested. The observation of partial decoherence in EPR systems could be a sig- nal for New Physics: we have tested for such effects, and found our results are consistent with no decoherence.

•Jan 1, 2007•0 citations

Quantum Entanglement and Decoherence at the Υ(5S) decay

A. Liese

In this thesis, we study the quantum entanglement of neutral B-mesons from the decay of the Υ(5S). The experiment which provided real data for this decay is the Belle experiment which ran from 1999 to 2010 and gathered about 121fb−1 of data for the Υ(5S). The decay of the Υ(5S) particle is expected to produce entangled pairs of neutral B-mesons, therefore any deviations of the theoretical predictions for such entangled pairs to the measured data can be attributed to an effect called Quantum Decoherence (QD). QD is a more general term for the loss of the quantum properties of a system. In this thesis QD will refer specifically to the loss of entanglement (=ˆ disentanglement). To start with, we will briefly go over the basics of the flavor physics of the neutral meson system and study effects of mixing and the time dependence of the flavor states for B0 mesons. Then we will use this framework to calculate the theoretical probability density of measuring possible states for these entangled systems and compare them to the disentangled system. We will further analyse how QD can manifest by considering the entanglement of formation, which refers to a system that consists of multiple entangled states. It will be shown how disentanglement can arise in such systems and then apply this theory directly to the B0-meson systems we expect from the Υ(5S) decay. In the end, there is a brief introduction to the experimental uncertainties of the Belle detector, which is captured by the resolution function, and its impact on the theoretical prediction.

•Apr 30, 2025•0 citations

Entanglement studies with Belle Upsilon(5S) Monte Carlo data

V. Geier

In this work, we study the entanglement of the B mesons produced in Upsilon(5S) decays into the final states each with C = ±1 eigenvalue Upsilon(5S) to B0B0-bar (C = -1), Upsilon(5S) to B0B0-bar* + c.c. (C = +1), Upsilon(5S) to B0*B0-bar* (C = -1). For this purpose, we use Belle Monte Carlo data. The B mesons are reconstructed from hadronic decays: B0 to D-pi+, with D- to K+pi-pi- B0 to D*-pi+, with D*- to D0-bar pi_s- and D0-bar to K+pi-, B0 to D*-pi+, with D*- to D0-bar pi_s- and D0-bar to K+pi-pi+pi-. We then determine the decay–time difference of the B meson pairs to investigate the time depen- dence of their quantum entanglement. Since an entanglement analysis has never been performed for Upsilon(5S) decays, this thesis establishes the foundation for such a study. This includes deriving the theoretical framework of entanglement at the Upsilon(5S), performing the necessary kinematic consider- ations for the decaytime calculation, and developing new time and flavor variables for the analysis, since the Belle II software framework is only partially applicable to the Upsilon(5S)) case. In addition, we generate Signal Monte Carlo samples of 1 x 10^6 B0(*)B0-bar(*) events to increase statistical precision. In the Upsilon(5S) system, it is possible to obtain two different types of entanglement. When these two types are mixed, one obtains a disentangled state, with the degree of disentanglement being equal to the mixing ratio of the two entangled states. By applying the model of partial spontaneous disentanglement (PSD), which introduces a fraction zeta, we can measure this disentanglement frac- tion when mixing the states and thereby validate the theoretical prediction. To achieve this, we implemented the PSD framework for the Upsilon(5S) case. We verified that, when mixing the two en- tangled states in equal proportions, the expected disentanglement fraction of 100% is successfully reproduced.

•Nov 1, 2025•0 citations

Study of Quantum Decoherence in Neutral B Meson pairs produced at the $\Upsilon(5S)$ Resonance

Louise Beriet

This thesis presents the development and validation of an analysis framework to study quantum decoherence in neutral B-meson pairs produced at the $\Upsilon(5S)$ resonance, using Monte Carlo simulated data from the Belle experiment. Unlike the $\Upsilon(4S)$, the $\Upsilon(5S)$ provides access to both antisymmetric ($C=-1$) and symmetric ($C=+1$) quantum states through the channels $B^0\bar{B}^0$, $B^{0*}\bar{B}^0+c.c.$, and $B^{0*}\bar{B}^{0*}$. Decoherence effects are studied with the Partial Spontaneous Disentanglement model, which introduces a fraction $\zeta$ of $B^{0*}\bar{B}^{*0}$ pairs disentangled at production. The analysis exploits the decay times of both neutral B mesons, for which time-dependent probability density functions are derived and extended to include detector-resolution effects. The framework is first validated on Signal Monte Carlo samples, where one-dimensional fits to $\Sigma t$ successfully recover the expected decoherence values for both entangled and disentangled configurations. Fits to Generic Monte Carlo samples, which include realistic backgrounds and event compositions, reveal strong correlations between the decoherence parameter and flavour-tagging wrong-tag fractions, particularly in the $C=-1$ channels. The results from these fits show significant deviations from expected $\zeta$ values and large uncertainties. Pure Toy Monte Carlo studies confirm that the fitter behaves linearly with respect to the injected decoherence parameter and show only small biases consistent with those observed in the nominal fits, but too small to fully explain them. To address the limitations of the single fits, a two-dimensional analysis in $(\Delta t,\Sigma t)$ is developed. By exploiting the full time-dependent information, the two-dimensional fit significantly reduces the statistical uncertainty on the decoherence parameter from $\sim\mathcal{O}(10\%)$ to $\sim\mathcal{O}(4\%)$ and mitigates correlations with the flavour-tagging parameters. This work constitutes a proof of concept for future analyses on Belle data and demonstrates the potential of the $\Upsilon(5S)$ system for studying quantum entanglement and decoherence in neutral B mesons.

•Jan 1, 2026•0 citations

Einstein-Podolsky-Rosen State of Neutral Mesons: The Entangled Partner of K_L Is Not K_S

Yu Shi

In a $ϕ$ factory, neutral kaons are produced in Einstein-Podolsky-Rosen (EPR) states, furthermore, a $K_S$ is tagged if its entangled partner is detected as $K_L$, and vice versa. Here we point out that upon its detection as $K_L$, one of the EPR-entangled particles is projected into one of the orthogonal basis states, consequently the other particle should be projected to the state orthogonal to $K_L$, denoted as $K_{\perp L}$, rather than $K_S$, because $K_S$ is not orthogonal to $K_L$. Therefore the semileptonic charge asymmetry of what was previously regarded as $K_S$ is really that of $K_{\perp L}$. Based on this re-tagging, we modify the experimentally determined values of several parameters, including the one describing the violation of $ΔS = ΔQ$ rule, the one describing CPT violation for $ΔS = ΔQ$ transitions, and the time-like CPT- and Lorentz-violating coefficient for the two valence quarks in a kaon.

arXiv:1202.2948•Feb 14, 2012•0 citations

CPT violation in entangled B0 – B¯0 states and the demise of flavour tagging

Ezequiel Álvarez, J. Bernabéu, Nick E. Mavromatos +2 more

We discuss the demise of flavour tagging due to the loss of the particle–antiparticle identity of neutral B -mesons in the Einstein–Podolsky–Rosen correlated states. Such a situation occurs in cases where the CPT operator is ill-defined, as happens, for example, in quantum gravity models with induced decoherence in the matter sector. The time evolution of the perturbed B 0 – B ¯ 0 initial state, as produced in B -factories, is sufficient to generate new two-body states. For flavour specific decays at equal times, we discuss two definite tests of the two body entanglement: (i) search for the would-be forbidden B 0 B 0 and B ¯ 0 B ¯ 0 states; (ii) deviations from the indistinguishable probability between the permuted states B ¯ 0 B 0 and B 0 B ¯ 0 .

arXiv:hep-ph/0410409•Physics Letters B•Dec 24, 2004•19 citations
The neutral B meson pair produced at the Upsilon(4S) should exhibit a nonlocal correlation of the type discussed by Einstein, Podolsky, and Rosen. We measure this correlation using the time-dependent flavor asymmetry of semileptonic B(0) decays, which we compare with predictions from quantum mechanics and two local realistic models. The data are consistent with quantum mechanics, and inconsistent with the other models. Assuming that some B pairs disentangle to produce B(0) and B(0) with definite flavor, we find a decoherent fraction of 0.029 +/ -0.057, consistent with no decoherence.
The neutral B-meson pair produced at the U(4S) should ex- hibit a non-local correlation of the type discussed by Einstein, Podol- ski, and Rosen. The time-dependent flavour asymmetry of the B mesons decaying into flavour eigenstates is used to test such a cor- relation. The asymmetry obtained from semileptonic B 0 decays is in agreement with the prediction from quantum mechanics and far away from the predictions of the local realistic models tested. The observation of partial decoherence in EPR systems could be a sig- nal for New Physics: we have tested for such effects, and found our results are consistent with no decoherence.
In this thesis, we study the quantum entanglement of neutral B-mesons from the decay of the Υ(5S). The experiment which provided real data for this decay is the Belle experiment which ran from 1999 to 2010 and gathered about 121fb−1 of data for the Υ(5S). The decay of the Υ(5S) particle is expected to produce entangled pairs of neutral B-mesons, therefore any deviations of the theoretical predictions for such entangled pairs to the measured data can be attributed to an effect called Quantum Decoherence (QD). QD is a more general term for the loss of the quantum properties of a system. In this thesis QD will refer specifically to the loss of entanglement (=ˆ disentanglement). To start with, we will briefly go over the basics of the flavor physics of the neutral meson system and study effects of mixing and the time dependence of the flavor states for B0 mesons. Then we will use this framework to calculate the theoretical probability density of measuring possible states for these entangled systems and compare them to the disentangled system. We will further analyse how QD can manifest by considering the entanglement of formation, which refers to a system that consists of multiple entangled states. It will be shown how disentanglement can arise in such systems and then apply this theory directly to the B0-meson systems we expect from the Υ(5S) decay. In the end, there is a brief introduction to the experimental uncertainties of the Belle detector, which is captured by the resolution function, and its impact on the theoretical prediction.
In this work, we study the entanglement of the B mesons produced in Upsilon(5S) decays into the final states each with C = ±1 eigenvalue Upsilon(5S) to B0B0-bar (C = -1), Upsilon(5S) to B0B0-bar* + c.c. (C = +1), Upsilon(5S) to B0*B0-bar* (C = -1). For this purpose, we use Belle Monte Carlo data. The B mesons are reconstructed from hadronic decays: B0 to D-pi+, with D- to K+pi-pi- B0 to D*-pi+, with D*- to D0-bar pi_s- and D0-bar to K+pi-, B0 to D*-pi+, with D*- to D0-bar pi_s- and D0-bar to K+pi-pi+pi-. We then determine the decay–time difference of the B meson pairs to investigate the time depen- dence of their quantum entanglement. Since an entanglement analysis has never been performed for Upsilon(5S) decays, this thesis establishes the foundation for such a study. This includes deriving the theoretical framework of entanglement at the Upsilon(5S), performing the necessary kinematic consider- ations for the decaytime calculation, and developing new time and flavor variables for the analysis, since the Belle II software framework is only partially applicable to the Upsilon(5S)) case. In addition, we generate Signal Monte Carlo samples of 1 x 10^6 B0(*)B0-bar(*) events to increase statistical precision. In the Upsilon(5S) system, it is possible to obtain two different types of entanglement. When these two types are mixed, one obtains a disentangled state, with the degree of disentanglement being equal to the mixing ratio of the two entangled states. By applying the model of partial spontaneous disentanglement (PSD), which introduces a fraction zeta, we can measure this disentanglement frac- tion when mixing the states and thereby validate the theoretical prediction. To achieve this, we implemented the PSD framework for the Upsilon(5S) case. We verified that, when mixing the two en- tangled states in equal proportions, the expected disentanglement fraction of 100% is successfully reproduced.
Study of Quantum Decoherence in Neutral B Meson pairs produced at the Υ(5S)\Upsilon(5S)Υ(5S) Resonance
This thesis presents the development and validation of an analysis framework to study quantum decoherence in neutral B-meson pairs produced at the Υ(5S)\Upsilon(5S)Υ(5S) resonance, using Monte Carlo simulated data from the Belle experiment. Unlike the Υ(4S)\Upsilon(4S)Υ(4S), the Υ(5S)\Upsilon(5S)Υ(5S) provides access to both antisymmetric (C=−1C=-1C=−1) and symmetric (C=+1C=+1C=+1) quantum states through the channels B0Bˉ0B^0\bar{B}^0B0Bˉ0, B0∗Bˉ0+c.c.B^{0*}\bar{B}^0+c.c.B0∗Bˉ0+c.c., and B0∗Bˉ0∗B^{0*}\bar{B}^{0*}B0∗Bˉ0∗. Decoherence effects are studied with the Partial Spontaneous Disentanglement model, which introduces a fraction ζ\zetaζ of B0∗Bˉ∗0B^{0*}\bar{B}^{*0}B0∗Bˉ∗0 pairs disentangled at production. The analysis exploits the decay times of both neutral B mesons, for which time-dependent probability density functions are derived and extended to include detector-resolution effects. The framework is first validated on Signal Monte Carlo samples, where one-dimensional fits to Σt\Sigma tΣt successfully recover the expected decoherence values for both entangled and disentangled configurations. Fits to Generic Monte Carlo samples, which include realistic backgrounds and event compositions, reveal strong correlations between the decoherence parameter and flavour-tagging wrong-tag fractions, particularly in the C=−1C=-1C=−1 channels. The results from these fits show significant deviations from expected ζ\zetaζ values and large uncertainties. Pure Toy Monte Carlo studies confirm that the fitter behaves linearly with respect to the injected decoherence parameter and show only small biases consistent with those observed in the nominal fits, but too small to fully explain them. To address the limitations of the single fits, a two-dimensional analysis in (Δt,Σt)(\Delta t,\Sigma t)(Δt,Σt) is developed. By exploiting the full time-dependent information, the two-dimensional fit significantly reduces the statistical uncertainty on the decoherence parameter from ∼O(10%)\sim\mathcal{O}(10\%)∼O(10%) to ∼O(4%)\sim\mathcal{O}(4\%)∼O(4%) and mitigates correlations with the flavour-tagging parameters. This work constitutes a proof of concept for future analyses on Belle data and demonstrates the potential of the Υ(5S)\Upsilon(5S)Υ(5S) system for studying quantum entanglement and decoherence in neutral B mesons.
In a ϕϕϕ factory, neutral kaons are produced in Einstein-Podolsky-Rosen (EPR) states, furthermore, a KSK_SKS​ is tagged if its entangled partner is detected as KLK_LKL​, and vice versa. Here we point out that upon its detection as KLK_LKL​, one of the EPR-entangled particles is projected into one of the orthogonal basis states, consequently the other particle should be projected to the state orthogonal to KLK_LKL​, denoted as K⊥LK_{\perp L}K⊥L​, rather than KSK_SKS​, because KSK_SKS​ is not orthogonal to KLK_LKL​. Therefore the semileptonic charge asymmetry of what was previously regarded as KSK_SKS​ is really that of K⊥LK_{\perp L}K⊥L​. Based on this re-tagging, we modify the experimentally determined values of several parameters, including the one describing the violation of ΔS=ΔQΔS = ΔQΔS=ΔQ rule, the one describing CPT violation for ΔS=ΔQΔS = ΔQΔS=ΔQ transitions, and the time-like CPT- and Lorentz-violating coefficient for the two valence quarks in a kaon.
We discuss the demise of flavour tagging due to the loss of the particle–antiparticle identity of neutral B -mesons in the Einstein–Podolsky–Rosen correlated states. Such a situation occurs in cases where the CPT operator is ill-defined, as happens, for example, in quantum gravity models with induced decoherence in the matter sector. The time evolution of the perturbed B 0 – B ¯ 0 initial state, as produced in B -factories, is sufficient to generate new two-body states. For flavour specific decays at equal times, we discuss two definite tests of the two body entanglement: (i) search for the would-be forbidden B 0 B 0 and B ¯ 0 B ¯ 0 states; (ii) deviations from the indistinguishable probability between the permuted states B ¯ 0 B 0 and B 0 B ¯ 0 .