Einstein's Boxes: Quantum Mechanical Solution
  In this paper we present a solution of the Einstein's boxes paradox by modern Quantum Mechanics in which a notion of density matrix is equivalent to a notion of a quantum state of a system. We use a secondary quantization formalism in the attempt to make a description particularly clear. The aim of this paper is to provide pedagogical help to the students of quantum mechanics. 
E.Yu.Bunkova, O.A.Khrustalev, O.D. Timofeevskaya