Decoherence effects in entangled fermion pairs at colliders

Abstract

Recent measurements at the Large Hadron Collider have observed entanglement in the spins of $t\bar{t}$ pairs. The effects of radiation, which are expected to lead to quantum decoherence and a reduction of entanglement, are generally neglected in such measurements. In this work we calculate the effects of decoherence from various different types of radiation for a maximally entangled pair of fermions -- a bipartite system of qubits in a Bell state. We identify the Kraus operators describing the evolution of the open quantum system with the integrated Altarelli-Parisi splitting functions.

Comments: 5 pages, 2 figures + supplemental Material; v2: journal version