Analysis of the entanglement between two individual atoms using global Raman rotations

TL;DR

This paper demonstrates a method to analyze and quantify entanglement between two individually trapped atoms using global Raman rotations, even accounting for atom losses and states outside the qubit basis.

Contribution

It introduces a detailed analysis technique for entanglement measurement that includes partial density matrix reconstruction considering atom losses.

Findings

Achieved a fidelity of 0.74 for entangled atom pairs

Successfully reconstructed the density matrix including outside-qubit states

Quantified entanglement despite atom losses during the sequence

Abstract

Making use of the Rydberg blockade, we generate entanglement between two atoms individually trapped in two optical tweezers. In this paper we detail the analysis of the data and show that we can determine the amount of entanglement between the atoms in the presence of atom losses during the entangling sequence. Our model takes into account states outside the qubit basis and allows us to perform a partial reconstruction of the density matrix describing the two atom state. With this method we extract the amount of entanglement between pairs of atoms still trapped after the entangling sequence and measure the fidelity with respect to the expected Bell state. We find a fidelity $F_{\rm pairs} =0.74(7)$ for the 62% of atom pairs remaining in the traps at the end of the entangling sequence.