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
KS state, an unsolved problem since the discovery of
CP 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.
The Einstein-Podolsky-Rosen (EPR) entanglement of a neutral K-meson (kaon) pair enjoys the peculiar quantum behaviour of mixing, charge-parity
CP violation (
C - charge conjugation,
P - parity) and two non-orthogonal eigenstates of definite time evolution
KL and
KS with very different lifetimes. The dynamics of this strange entanglement, experimentally accessible at the
ϕ-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
t1 and
t2 with
Δt=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
t2 from the observation of the first decay channel at
t1, and future to past, leading to the past state of the decayed kaon at time
t1 from the observation of the second decay channel at
t2. 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, at large decoherence times the resulting first decayed state is always
KS, providing a genuine tag of this kaon state in the decoherence region, and a unique and important experimental tool to prepare a pure
KS beam.
Novel quantum phenomena have been recently discussed 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 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
ΦNE collider are presented, showing experimental evidence of this new effect.
In a
ϕ factory, neutral kaons are produced in Einstein-Podolsky-Rosen (EPR) states, furthermore, a
KS is tagged if its entangled partner is detected as
KL, and vice versa. Here we point out that upon its detection as
KL, 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
KL, denoted as
K⊥L, rather than
KS, because
KS is not orthogonal to
KL. Therefore the semileptonic charge asymmetry of what was previously regarded as
KS is really that of
K⊥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.
This chapter provides an in-depth analysis of the properties and phenomena associated with neutral K-mesons. Kaons are quantum systems illustrating strange behaviors. We begin by examining the significance of strangeness and charge parity violation in understanding these particles. The concept of strangeness oscillations is then introduced, explaining oscillations between K0 and K¯0 states. The regeneration of KS is investigated, uncovering the underlying mechanisms involved. The discussion moves on to quasi-spin space, exploring its bases and their implications. The entangled states of kaon pairs K0K¯0 are considered, with a focus on maximally entangled neutral kaons and nonmaximally entangled states. Decoherence effects on entangled kaons are examined, utilizing the density matrix description to capture the dynamics. A dedicated decoherence parameter is introduced to quantify the impact of decoherence. Furthermore, the chapter investigates the loss of entanglement through measures such as von Neumann entanglement entropy, entanglement of formation, and concurrence. These measures provide insights into quantifying and characterizing entanglement in the context of neutral kaons. Through this comprehensive exploration of properties, phenomena, and entanglement dynamics, this chapter aims to pointing out recent works on neutral kaons, contributing to advancements in particle physics.