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The European Physical Journal C

Searching for evolutions from pure states into mixed states with entangled neutral kaons

H.-J. Gerber

Published Jan 1, 2004• 4 citations
Publisher
DOI
10.1140/epjc/s2003-01382-2

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Comment on ``Searching for Evolutions of Pure States into Mixed States in the Two-State System K-K''

Fabio Benatti, Roberto Floreanini B

It has been recently proposed to study generic dynamical evolutions of the neutral kaon system that go beyond quantum mechanics. We explicitly show that, unless the condition of complete positivity is enforced, those dynamics are physically inconsistent and should be rejected.

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

J. Bernabéu, ANTONIO DI DOMENICO

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.

•Dec 10, 2019•1 citation
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.