KIP-Veröffentlichungen

Whether quantum correlations between identical particles can serve as a resource for quantum information protocols has often been questioned, since the constituent particles are not individually addressable. In this work, a scheme is presented that converts these correlations into entanglement between distinct spatial modes. Starting with a Bose-Einstein condensate (BEC) of Rb-87 in a tightly confining trap, we use spin-mixing to generate a quantum correlated state of indistinguishable particles in a single spatial mode. This entanglement is subsequently distributed in space by expanding the atomic cloud which can be viewed as splitting the BEC in the spatial degree of freedom. Using a spatially resolved spin readout we demonstrate a particularly strong form of entanglement known as Einstein-Podolsky-Rosen (EPR) steering between spatially distinct regions of the expanded BEC. This certifies that the prepared state is indeed a useful resource for quantum information protocols. Additionally, we developed a new readout technique based on coupling the spin state to initially unoccupied auxiliary modes. This splitting in the internal degree of freedom enables the simultaneous and spatially resolved extraction of multiple noncommuting observables. We show that this technique is capable of detecting quantum correlations by measuring fluctuations below the standard quantum limit. This results in a new method to characterize quantum states and together with the spatial resolution provides the possibility to detect entanglement in complex multimode settings. Combining these two results provides the prospect of studying the generation of cluster states, which are the crucial resource for one-way quantum computation. This renders BECs a new test bed for quantum information tasks.