P03 - Causality in Quantum Information

Časlav Brukner


Research on quantum causal structures is a new and rapidly evolving field that has a potential not only to achieve enhanced functionalities of information processing but also to make a radical departure from the classical understanding of space-time with fixed causal structures [R03-1, R03-2, R03-3]. It is known that quantum information processing on indefinite causal structures offers linear advantages in regard to query complexity [R03-2, R03-4] and exponential advantage in communication complexity [R03-6]. Still the research field is at its beginning, largely fragmented and many questions are open.

The long-term goals and visions of our project are to (i) provide a complete operational formalism for quantum (field) theory with no global background causal structure, (ii) understand models of quantum computation and communication on indefinite causal structures and identify problems where they outperform information processing with a fixed order of gates, and (iii) bring the field closer to experimental realizations.

PI Časlav Brukner on
Causality in Quantum Information


Subproject Leader: Časlav Brukner

Co-PIs: Ämin Baumeler, Costantino Budroni

PostDoc: Marco Túlio Coelho Quintino

PhDs: Martin Johannes Renner


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

Communication through quantum-controlled noise
P. A. Guerin, G. Rubino, Č. Brukner
Phys. Rev. A 99, 062317 (2019)

Semi-device-independent certification of indefinite causal order
J. Bavaresco, M. Araujo, Č. Brukner, M.T. Quintino
QUANTUM, 3, 176 (2019)

Other publications:

Exponential Communication Complexity Advantage from Quantum Superposition of the Direction of Communication
P. A. Guérin, A. Feix, M. Araújo, Č. Brukner
Phys. Rev. Lett. 117, 100502 (2016)

Witnessing causal nonseparability
M. Araújo, C. Branciard, F. Costa, A. Feix, C. Giarmatzi, Č. Brukner
New J. Phys. 17, 102001 (2015)

Computational advantage from quantum-controlled ordering of gates
M. Araujo, F. Costa, Č. Brukner
Phys. Rev. Lett. 113, 250402 (2014)

For further publications: see here.