• Mathematical aspects of identifying entangled quantum states (entanglement witnesses, nonlinear entanglement criteria, spin squeezing inequalities)

  • Methods for the experimental creation and detection of entanglement in quantum optical systems (photonic systems, spin squeezing in cold atomic ensembles, optical lattices of cold atoms)
  • Multi-particle singlet states in cold gases (see link at Morgan W. Mitchell's group)

  • Multi-particle entanglement of Dicke states

  • Scalable state tomography (Permutationally Invariant Quantum Tomography)

  • Application of entangled quantum states for quantum metrology (e.g., differential magnetometry with cold atomic ensembles)

  • Quantum Fisher Information and its relation to multipartite entanglement

  • Foundations of quantum theory (Bell inequalities and local hidden variable models)


1. Polytope of separable states for the Optimal Spin Squeezing Inequalities. [Figure from Phys. Rev. Lett. 99, 25045 (2007); Phys. Rev. A 79, 042334 (2009).] 

2. Setup generating a four-qubit symmetric Dicke state with two excitations with parametric down-conversion in a BBO crystal, linear optical elements and detectors. [Figure from Phys. Rev. Lett. 98, 063604 (2007).]

3. Results of Permutationally Invariant Tomography in a four-photon experiment [Figure from Phys. Rev. Lett. 105, 250403 (2010).]