Manipulating quantum entanglement of quasiparticles in many-electron systems by attosecond x-ray pulses

Photoexcited electrons and holes in molecules or in semiconductors constitute a bipartite entangled system. We show that this entanglement can be coherently controlled by broadband x-ray pulses which create valence excitation wave packets through a stimulated Raman process. A novel measure of electron correlations in excited states is then provided by the time dependence of the concurrence. In a simulation study we demonstrate the control of entanglement of electrons and holes in CO that can be achieved by tuning a soft x-ray pulse to different core transitions: the carbon K edge (296 eV), the oxygen K edge (540 eV), and the 2σ→1π* transition (191 eV).