Eur. Phys. J. D 59, 317-320 (2010)
https://doi.org/10.1140/epjd/e2010-00150-4

A tight bound on negativity of superpositions

School of physics and optoelectronic technology, Dalian University of Technology, 116024, Dalian, P.R. China

Corresponding author: ^a quaninformation@sina.com

Received: 23 December 2009
Revised: 25 February 2010
Published online: 4 June 2010

Abstract

By a variational definition of the entanglement measure – negativity, we derive an upper bound of negativity of superpositions in terms of the negativities of the quantum states being superposed. It is shown that the upper bound has a simple formulation. In particular, in many cases the upper bound is tighter than the previous bounds.