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Journal of Physics Conference Series

Can future observation of the living partner post-tag the past decayed state in entangled neutral K-mesons?

ANTONIO DI DOMENICO

Published Feb 1, 2023• 2 citations

Abstract

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.

DOI: 10.1088/1742-6596/2446/1/012027

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Journal of High Energy Physics•Apr 8, 2022•10 citations

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

\phi

-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 DA

\Phi

NE collider are presented, showing experimental evidence of this new effect.

Entangled neutral

K

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

{K}_{S}

state, an unsolved problem since the discovery of

CP

violation.

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.

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

{\cal C}

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.

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

\phi\rightarrow K_SK_L\rightarrow\pi^+\pi^-\pi^+\pi^-

exhibits the characteristic Einstein-Podolsky-Rosen correlations that prevent both kaons to decay into

\pi^+\pi^-

at the same time. The newly published result is based on data sample collected with the KLOE detector at DA

\Phi

NE and corresponds to an integrated luminosity of about 1.7 fb

^{-1}

, i.e. to

\sim

1.7

\times

10

^9

\phi\rightarrow K_SK_L

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

\phi \rightarrow K_S K_S , K_L K_L

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:

K_S K_L \to (\pi^{\pm}e^{\mp}\nu)(3\pi^0)

and

K_S K_L \to (\pi^{\pm}e^{\mp}\nu)(3\pi^0)

. 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.

Precision tests of quantum mechanics and

\mathcal{CPT}

symmetry with entangled neutral kaons at KLOE

Abstract The quantum interference between the decays of entangled neutral kaons is studied in the process ϕ → KSKL → π+π−π+π−, which exhibits the characteristic Einstein-Podolsky-Rosen correlations that prevent both kaons to decay into π+π− at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and

\mathcal{CPT}

CPT violation effects, which may be justified in a quantum gravity framework. The analysed data sample was collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory, and corresponds to an integrated luminosity of about 1.7 fb−1, i.e. to about 1.7 × 109ϕ → KSKL decays produced. From the fit of the observed ∆t distribution, being ∆t the difference of the kaon decay times, the decoherence and

\mathcal{CPT}

CPT violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses. The results are consistent with no deviation from quantum mechanics and

\mathcal{CPT}

CPT symmetry, while for some parameters the precision reaches the interesting level at which — in the most optimistic scenarios — quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.