2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/92001Quantum marking and quantum erasure are discussed for the neutral kaon system. Contrary to other two-level systems, strangeness and lifetime of a neutral kaon state can be alternatively measured via an "active" or a "passive" procedure. This offers new quantum erasure possibilities. In particular, the operation of a quantum eraser in the "delayed choice" mode is clearly illustrated.12 pages, contribution to the Festschrift in honor of Prof. Jose Adolfo de Azcarraga for his 60th birthday, Salamanca (Spain), June 9-11, 2003Quantum PhysicsHigh Energy Physics - Phenomenologytext