Comparisons of entanglement witnesses for n-qubit systems

Kathleen Walsh, Andrew Schauf, Joseph Lesniak +3 more

Justyna P. Zwolak, Dariusz Chru 'sci 'nski

Kathleen Walsh, Elizabeth Behrman, James E. Steck +1 more

Jan Roik, Karol Bartkiewicz, Antonín Černoch +1 more

Detection of entangled states is essential in both fundamental and applied quantum physics. However, this task proves to be challenging especially for general quantum states. One can execute full state tomography but this method is time demanding especially in complex systems. Other approaches use entanglement witnesses, these methods tend to be less demanding but lack reliability. Here, we demonstrate that ANN -- artificial neural networks provide a balance between both approaches. In this paper, we make a comparison of ANN performance against witness-based methods for random general 2-qubit quantum states without any prior information on the states. Furthermore, we apply our approach to real experimental data set.

X. Wang, Klaus Mølmer

Waldemar Kłobus, Paweł Cieśliński, Lukas Knips +2 more

We study the possibility of witnessing Gaussian entanglement between two continuous-variable systems with the help of two spatially separated qubits. Its key ingredient is a local lossy state transfer from the original systems onto local qubits. The qubits are initially in a pure product state, therefore by detecting entanglement between the qubits we witness entanglement between the two original systems.