Entanglement of Orbital Angular Momentum in Non-Sequential Double Ionization

Abstract

We demonstrate entanglement between the orbital angular momentum (OAM) of two photoelectrons ionized via the strongly correlated process of non-sequential double ionization (NSDI). Due to the quantization of OAM, this entanglement is easily quantified and has a simple physical interpretation in terms of conservation laws. We explore detection by an entanglement witness, decomposable into local measurements, which strongly reduces the difficulty of experimental implementation. We compute the logarithmic negativity measure, which is directly applicable to mixed states, to demonstrate that the entanglement is robust to incoherent effects such as focal averaging. Using the strong-field approximation, we quantify the entanglement for a large range of targets and field parameters, isolating the best targets for experimentalists. The methodology presented here provides a general way to use OAM to quantify and, in principle, measure entanglement, that is well-suited to attosecond processes, can enhance our understanding and may be exploited in imaging processes or the generation of OAM-entangled electrons.

Theory of entanglement and measurement in high harmonic generation

“…Considering that HHG from more complex materials such as solids or plasma [56][57][58][59][60], strongly correlated [61], or topological systems [62][63][64][65][66] follows very similar mechanism anticipates for further investigation of the non-classical properties from the interaction with such materials. In particular, entanglement in strong field driven processes, for instance, between the ion and ionized electron [67], or in two-electron ionization [68] are of current interest. The connection to quantum information science will ultimately help to answer the question of the quantum mechanical properties in intense laser matter interaction from atoms to complex materials, and how new quantum states of light with the use for modern quantum technologies can be generated.…”