CMS results on top spin correlations and entanglement

Quantum entanglement of top and antitop quarks based on the spin degrees of freedom has been demonstrated using LHC data collected by the CMS experiment in the period of 2016-2018. Top quark decays to a bottom quark and a $W$ boson, which decays ether leptonically or to a quark-antiquark pair. Pair production of top quarks with both $W$ bosons decaying leptonically is referred to as a dilepton channel, since it contains two charged leptons. The channel containing one of the $W$ bosons decaying into a quark-antiquark pair, is referred to as a lepton+jets channel. We present the results in both channel. Using the opening angle between the two charged leptons, an entanglement has been demonstrated at the threshold of the top pair production in the dilepton channel. Using lepton+jets channel we perform a measurement of the top and antitop quark polarization and spin correlation in bins of the invariant mass of the system and the top quark scattering angle. Using the spin correlation matrix we demonstrate the entanglement at the production threshold and at the high invariant mass.