Entanglement in the Kondo Spin Chain Abolfazl Bayat 1, Sougato Bose 1, Pasquale Sodano 2 1 University College London, London, UK. 2 University of Perugia, Perugia, Italy. Engineering of States and Devices: Theory and Experiments

Contents of the Talk Condensed Matter Quantum Information 1. Kondo physics 2. Entanglement in the Kondo ground state 3. Generating a long range entanglement

Gapped Systems Ground state Excited states The intrinsic length scale of the system impose an exponential decay

Gapless Systems Ground state Continuum of excited states There is no length scale in the system so correlations decay algebraically

Kondo Physics Despite the gapless nature of the Kondo system, correlations decay exponentially

Kondo Spin Chain E. S. Sorensen et al., J. Stat. Mech., P08003 (2007)

Entanglement as a Witness of the Cloud A B Impurity L

Scaling Kondo Phase: Dimer Phase: A B Impurity L N-L-1

Scaling Properties of the Kondo regime Kondo Phase: Dimer Phase:

Local Quench Quench

Kondo versus Dimer

Optimal Parameter

Optimality and Distance independence Independent of length N, when cloud contains N-2 spins we generate a constant Entanglement

Modified Strategy

Entanglement in the Modified Strategy Kondo: High value distance independent entanglement mediated by the cloud. Dimer: Entanglement is just due to an end-end effect which decays exponentially.

More fun with Kondo

Entanglement Rotor Dispatching centre With interacting the clouds impurities get entangled

Summary of Results With using the entanglement measures, one can capture the properties of the Kondo physics. A local quench generates an oscillatory dynamics in the Kondo regime. Kondo cloud mediates long range distance independent entanglement between individual ending. References: 1- Abolfazl Bayat, Pasquale Sodano, Sougato Bose, Physical Review B 81, (2010) 2- Pasquale Sodano, Abolfazl Bayat, Sougato Bose, Physical Review B 81, (R) (2010)