Entanglement Negativity in Disordered Quantum Systems

  Yishai Schreiber  ,  Richard Berkovits  
Bar-Ilan University

Quantum negativity is a measure of quantum entanglement which, unlike entanglement entropy, is suitable also for mixed states. Thus it is also a good measure for entanglement between two parts of a larger system. Here we compute the negativity in disordered fermionic systems. We find that the negativity is log-normally distributed, and decaying with increasing disorder or distance between regions. Surprisingly, we find that even for regions separated by distances much larger than the localization length, there are rare cases where the negativity is relatively high, namely where far-apart regions are entangled. These cases are explained as necklace states, known also from optics of open systems, where the transmission does not decay as expected, due to resonances in the disordered system. Additionally we observe a correspondence between the negativity and the correlations in a given system.