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Can future observation influence the past of entangled neutral K-mesons?

J. Bernabéu, ANTONIO DI DOMENICO

Published Dec 10, 2019• 1 citation
OpenAlex

Abstract

The Einstein-Podolsky-Rosen (EPR) entanglement of a neutral K-meson (kaon) pair enjoys the peculiar quantum behaviour of mixing, charge-parity ${\cal CP}$ violation (${\cal C}$ - charge conjugation, ${\cal P}$ - parity) and two non-orthogonal eigenstates of definite time evolution $K_L$ and $K_S$ with very different lifetimes. The dynamics of this strange entanglement, experimentally accessible at the $\phi$-factory, makes possible the search for novel phenomena not accessible in any other system, i.e. at interference times and at decoherence times of the single partners after their disentanglement, in order to unveil the nature of the correlation between the two neutral kaons. Until now, the studies have been concentrated on the single kaon intensity distribution between the two decay times $t_1$ and $t_2$ with $\Delta t = t_2 - t_1 > 0$. Here we show that the entire two single time distributions, before each decay, are physical in both senses: past to future, leading to the state of the living partner at time $t_2$ from the observation of the first decay channel at $t_1$, and future to past, leading to the past state of the decayed kaon at time $t_1$ from the observation of the second decay channel at $t_2$. Our results thus demonstrate an affirmative answer to the title: it does, the past decayed state depends on the result of the future measurement for the living partner. This novel effect is truly observable through the first decay time distributions. Besides the implications for quantum physics for all $\Delta t$, at large decoherence times the resulting first decayed state is always $K_S$, providing a genuine tag of this kaon state in the decoherence region, and a unique and important experimental tool to prepare a pure $K_S$ beam.

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International Conference on High Energy Physics (ICHEP)•Nov 30, 2022•3 citations
The Einstein-Podolsky-Rosen (EPR) entanglement of a neutral K-meson (kaon) pair enjoys the peculiar quantum behaviour of mixing, charge-parity CP{\cal CP}CP violation (C{\cal C}C - charge conjugation, P{\cal P}P - parity) and two non-orthogonal eigenstates of definite time evolution KLK_LKL​ and KSK_SKS​ with very different lifetimes. The dynamics of this strange entanglement, experimentally accessible at the ϕ\phiϕ-factory, makes possible the search for novel phenomena not accessible in any other system, i.e. at interference times and at decoherence times of the single partners after their disentanglement, in order to unveil the nature of the correlation between the two neutral kaons. Until now, the studies have been concentrated on the single kaon intensity distribution between the two decay times t1t_1t1​ and t2t_2t2​ with Δt=t2−t1>0\Delta t = t_2 - t_1 > 0Δt=t2​−t1​>0. Here we show that the entire two single time distributions, before each decay, are physical in both senses: past to future, leading to the state of the living partner at time t2t_2t2​ from the observation of the first decay channel at t1t_1t1​, and future to past, leading to the past state of the decayed kaon at time t1t_1t1​ from the observation of the second decay channel at t2t_2t2​. Our results thus demonstrate an affirmative answer to the title: it does, the past decayed state depends on the result of the future measurement for the living partner. This novel effect is truly observable through the first decay time distributions. Besides the implications for quantum physics for all Δt\Delta tΔt, at large decoherence times the resulting first decayed state is always KSK_SKS​, providing a genuine tag of this kaon state in the decoherence region, and a unique and important experimental tool to prepare a pure KSK_SKS​ beam.
Entangled neutral K-mesons allow the study of their correlated dynamics at interference and decoherence times not accessible in any other system. We find novel quantum phenomena associated to a correlation-in-time between the two partners: the state of the first decayed Kaon, when it was entangled before its decay, is influenced by the result and the time of the future observation of the second decay channel. This surprising from future to past effect is fully observable and leads to the unique experimental tag of the KS-state, an unsolved problem since the discovery of CP violation.
Entangled neutral KKK mesons allow for the study of their correlated dynamics at interference and decoherence times not accessible in any other system. We find novel quantum phenomena associated to a correlation in time between the two partners: The past state of the first decayed kaon, when it was entangled before its decay, is post-tagged by the result and the time of the future observation of the second decay channel. This surprising ``from future to past'' effect is fully observable and leads to the unique experimental tag of the KS{K}_{S}KS​ state, an unsolved problem since the discovery of CPCPCP violation.
Abstract Novel quantum phenomena have been recently discussed [1] in association to a peculiar time correlation between entangled neutral kaons produced at a ϕ-factory: the past state of the first decayed kaon, when it was still entangled before its decay, is post-tagged by the result and the time of the future observation on the other kan decay. This surprising “from future to past” effect is fully observable and leads to the unique experimental tag of the KS state, an unsolved problem since the discovery of CP violation. The first preliminary results obtained on the analysis of data collected by the KLOE experiment at the DAΦNE collider, and showing experimental evidence of this new effect are presented.
Novel quantum phenomena have been recently discussed in association to a peculiar time correlation between entangled neutral kaons produced at a ϕ\phiϕ-factory: the past state of the first decayed kaon, when it was still entangled before its decay, is post-tagged by the result and the time of the future observation on the other kaon decay. This surprising ``from future to past'' effect is fully observable. Preliminary results obtained on the analysis of data collected by the KLOE experiment at the DAΦ\PhiΦNE collider are presented, showing experimental evidence of this new effect.
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.
The quantum interference between the decays of entangled neutral kaons is a very powerful tool for testing the quantum coherence of the entangled kaon pair state. The studied process ϕ→KSKL→π+π−π+π−\phi\rightarrow K_SK_L\rightarrow\pi^+\pi^-\pi^+\pi^-ϕ→KS​KL​→π+π−π+π− exhibits the characteristic Einstein-Podolsky-Rosen correlations that prevent both kaons to decay into π+π−\pi^+\pi^-π+π− at the same time. The newly published result is based on data sample collected with the KLOE detector at DAΦ\PhiΦNE and corresponds to an integrated luminosity of about 1.7 fb−1^{-1}−1 , i.e. to ∼\sim∼ 1.7 ×\times× 109^99 ϕ→KSKL\phi\rightarrow K_SK_Lϕ→KS​KL​ decays. From the fit to the observed time difference distribution of the two kaon decays, the decoherence and CPT violation parameters of various phenomenological models are measured. A stringent upper limit on the branching ratio of the ϕ→KSKS,KLKL\phi \rightarrow K_S K_S , K_L K_Lϕ→KS​KS​,KL​KL​ decay is also derived. Independently, the comparison of neutral meson transition rates between flavour and CP eigenstates allows direct and model independent tests of time-reversal T and CPT symmetries to be conducted, through ratios of rates of two classes of processes: KSKL→(π±e∓ν)(3π0)K_S K_L \to (\pi^{\pm}e^{\mp}\nu)(3\pi^0)KS​KL​→(π±e∓ν)(3π0) and KSKL→(π+π−)(π±e∓ν)K_S K_L \to (\pi^{+}\pi^{-})(\pi^{\pm}e^{\mp}\nu)KS​KL​→(π+π−)(π±e∓ν). In addition to this a straightforward extension to the case of CPT symmetry is performed providing the first model independent test of CPT symmetry violation in transitions of neutral kaons.