Non-linear electronic entanglement witness based on current cross correlations

Sammanfattning: Demonstration of entanglements of mobile electrons in solid state conductors using minimal entanglement linear witness from electrical current correlations has been given. However, detection of maximally entangled states and some mixed states is lacking if the witness is based on two cross correlation measurements only. This thesis is trying to detect them with the same number of measurements by investigating nonlinear witnesses which, in principle, should be able to detect more states than a linear witness. This is done theoretically with a generic entangler-detector setup. We found that all entangled states are detectable when considering pure states only but when considering mixed states, there is no improvement compared to a linear witness. This was done using the symmetries between the two operators corresponding to each measurement.