Quantum foundations and indefinite causal structures

Superposition of quantum operations


Optical elements

Our research covers also the investigation of quantum phenomena and the emergence of those as resource for the advantages of quantum information processing. In particular, we are interested in the superposition of causal orders, which are not only of fundamental interest but allow also additional speed-ups for particular quantum computational tasks. For the experimental realization of indefinite causal structures photonic systems provide unique advantages due to the intrinsic mobility. Recently we have also tested standard quantum mechanics against hyper-complex quantum theories and have demonstrated that quantum discord in some cases can outperform quantum entanglement for the remote quantum state preparation.


Publications (selected):

Experimental quantum communication enhancement by superposing trajectories
G. Rubino, L. A. Rozema, D. Ebler, H. Kristjánsson, S. Salek, P. Allard Guérin, A. A. Abbott, C. Branciard, C. Brukner, G. Chiribella, P. Walther,
Physical Review Research 3, 013093 (2021).

Single-Photon test of hyper-complex quantum theories using a metamaterial
L.M. Procopio, L.A. Rozema, Z. Jing Wong, D.R. Hamel, K. O'Brien, X. Zhang, B. Dakic, P. Walther,
Nature Communications 8, 15044 (2017).

Experimental verification of an indefinite causal order
G. Rubino, L.A. Rozema, A. Feix, M. Araújo, J.M. Zeuner, L.M. Procopio, C. Brukner, P. Walther,
Science Advances 3, e1602589 (2017).

Experimental superposition of orders of quantum gates
L.M. Procopio, A. Moqanaki, M. Araújo, F. Costa, I. Alonso Calafell, E.G. Dowd, D.R. Hamel, L.A. Rozema, Č. Brukner, P. Walther,
Nature Communications 6, 7913 (2015).

Quantum discord as optimal resource for remote state preparation
B. Dakic, Y.-O. Lipp, X.S. Ma, M. Ringbauer, S. Kropatschek, S. Barz, T. Paterek, V. Vedral, A. Zeilinger, C. Brukner, P. Walther,
Nature Physics 8, 666 (2012).

Further publications...