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

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)

Computational Advantage from a Quantum Superposition of Qubit Gate Orders
M. J. Renner and Č. Brukner
Phys. Rev. Lett. 128, 230503 (2022)

Inferring work by quantum superposing forward and time-reversal evolutions
G. Rubino, G. Manzano, L. A. Rozema, P. Walther, J. M. R. Parrondo, and Č. Brukner
Phys. Rev. Research 4, 013208 (2022)

Experimental entanglement of temporal order
G. Rubino, L. A. Rozema, F. Massa, M. Araújo, M. Zych, Č. Brukner, and P. Walther
Quantum 6, 621 (2022)

Noncausal Page-Wootters circuits
V. Baumann, M. Krumm, P. A. Guérin, Č. Brukner
Phys. Rev. Research 4, 013180 (2022)

Quantum superposition of spacetimes obeys Einstein's equivalence principle
F. Giacomini, Č. Brukner
AVS Quantum Sci. 4, 015601 (2022)

Transformation of spin in quantum reference frames
M. Mikusch, L. C. Barbado, Č. Brukner
Phys. Rev. Research 3, 043138 (2021)

Quantum superposition of thermodynamic evolutions with opposing time’s arrows
G. Rubino, G. Manzano, Č. Brukner
Communication Physics 4, 251 (2021)

Reassessing the computational advantage of quantum-controlled ordering of gates
M. J. Renner, Č. Brukner
Phys. Rev. Research 3, 043012 (2021)

Relativistic Bell Test within Quantum Reference Frames
L. F. Streiter, F. Giacomini, Č. Brukner
Phys. Rev. Lett. 126, 230403 (2021)

Simulating indefinite causal order with Rindler observers
A. Dimić, M. Milivojević, D. Gočanin, N. S. Móller, Č. Brukner
Front. Phys., 26 October (2020)

Quantum Temporal Superposition: The Case of Quantum Field Theory
L. J. Henderson, A. Belenchia, E. Castro-Ruiz, C. Budroni, M. Zych, Č. Brukner, R. B. Mann
Phys. Rev. Lett. 125, 131602 (2020)

Does violation of a Bell inequality always imply quantum advantage in a communication complexity problem?
A. Tavakoli, M. Żukowski, Č. Brukner
Quantum 4, 316 (2020)

Unruh effect for detectors in superposition of accelerations
L. C. Barbado, E. Castro-Ruiz, L. Apadula, Č. Brukner
Phys. Rev. D 102, 045002 (2020)

Quantum clocks and the temporal localisability of events in the presence of gravitating quantum systems
E. Castro-Ruiz, F. Giacomini, A. Belenchia, Č. Brukner
Nature Communications 11, 2672 (2020)

Relativistic Quantum Reference Frames: The Operational Meaning of Spin
F. Giacomini, E. Castro-Ruiz, Č. Brukner
Phys. Rev. Lett. 123, 090404 (2019)

Bell’s theorem for temporal order
M. Zych, F. Costa, I. Pikovski, Č. Brukner
Nature Communications 10, 3772 (2019)

A spacetime area law bound on quantum correlations
I. Kull, P. A. Guérin, Č. Brukner
npj Quantum Information 5, 48 (2019)

Information content of the gravitational field of a quantum superposition
A. Belenchia, R. M. Wald, F. Giacomini, E. Castro-Ruiz, Č. Brukner, M. Aspelmeyer
Int. J. Mod. Phys. D 1943001 (2019)

Quantum mechanics and the covariance of physical laws in quantum reference frames
F. Giacomini, E. Castro, and Č. Brukner
Nature Communications 10, 494 (2019)

Composition rules for quantum processes: a no-go theorem
P. Allard Guérin, M. Krumm, C. Budroni, Č. Brukner
New J. Phys. 21, 012001 (2019)

Equivalence of grandfather and information antinomy under intervention
A. Baumeler, E. Tselentis
Proceedings of the 17th International Conference on Quantum Physics and Logic, Electronic Proceedings in Theoretical Computer Science 340, 1 (2021)

Free energy of a general computation
A. Baumeler, S. Wolf
Physical Review D 100, 052115 (2019)

Experimental two-way communication with one photon
F. Massa, A. Moqanaki, A. Baumeler, F. Del Santo, J. A. Kettlewell, B. Dakić, P. Walther
Advanced Quantum Technologies 2, 1900050 (2019)

Reversible time travel with freedom of choice
A. Baumeler, F. Costa, T. Ralph, S. Wolf, M. Zych
Classical and Quantum Gravity 36, 224002 (2019)

Unlimited non-causal correlations and their relation to non-locality
A. Baumeler, A. Shiraz Gilani, J. Rashid
Quantum 6:673 (2022)

Equivalence of grandfather and information antinomy under intervention
A. Baumeler, E. Tselentis
Proceedings of the 17th International Conference on Quantum Physics and Logic (QPL2020), Electronic Proceedings in Theoretical Computer Science 340, (2021)

Temporal correlations in the simplest measurement sequences
L. Vieira, C. Budroni
Quantum 6, 623, (2022)

Ticking-clock performance enhanced by nonclassical temporal correlations
C. Budroni, G. Vitagliano, M. P. Woods
Phys. Rev. Research 3, 033051 (2021)

Device-independent quantification of measurement incompatibility
S.-L. Chen, N. Miklin, C. Budroni, Y.-N. Chen
Phys. Rev. Research 3, 023143 (2021)

Simulating extremal temporal correlations
C. Spee, C. Budroni, O. Gühne
New J. Phys. 22, 103037 (2020)

Memory cost of temporal correlations
C. Budroni, G. Fagundes, M. Kleinmann
New J. Phys. 21, 093018 (2019)

Device-independent tests of structures of measurement incompatibility
M. T. Quintino, C. Budroni, E. Woodhead, A. Cabello, D. Cavalcanti
Phys. Rev. Lett. 123, 180401 (2019)

Leggett-Garg macrorealism and the quantum nondisturbance conditions
R. Uola, G. Vitagliano, C. Budroni
Phys. Rev. A 100, 042117 (2019)

Bell nonlocality with a single shot
M. Araújo, F. Hirsch, M.T. Quintino
Quantum 4, 353 (2020)

Simple and maximally robust processes with no classical common-cause or direct cause explanation
M. Nery, M. T. Quintino, P. A. Guérin, T. O. Maciel, R. O. Vianna
Quantum 5, 538 (2021)

Certifying dimension of quantum systems by sequential projective measurements
A. Sohbi,D. Markham, J. Kim, M.T. Quintino
Quantum 5, 472 (2021)

Success-or-Draw: A Strategy Allowing Repeat-Until-Success in Quantum Computation
Q. Dong, M.T. Quintino, A. Soeda, M. Murao
Phys. Rev. Lett. 126, 150504 (2021)

Strict Hierarchy between Parallel, Sequential, and Indefinite-Causal-Order Strategies for Channel Discrimination
J. Bavaresco, M. Murao, M.T. Quintino
Phys. Rev. Lett. 127, 200504 (2021)

Deterministic transformations between unitary operations: Exponential advantage with adaptive quantum circuits and the power of indefinite causality
M.T. Quintino, D. Ebler
Quantum 6, 679 (2022)

Unitary channel discrimination beyond group structures: Advantages of sequential and indefinite-causal-order strategies
J. Bavaresco, M. Murao, M.T. Quintino, J.
Math. Phys. 63, 042203 (2022)

Detecting quantum non-breaking channels without entanglement
H.-Y. Ku, J. Kadlec, A. Cernoch, M.T. Quintino, W. Zhou, K. Lemr, N. Lambert, A. Miranowicz, S.-L. Chen,
F. Nori, Y-N. Chen
PRX Quantum 3, 020338 (2022)

Quantum teleportation of quantum causal structures
M. Krumm, P. A. Guérin, T. Zauner, Č. Brukner
preprint arXiv.2203.00433

Einstein's Equivalence principle for superpositions of gravitational fields and quantum reference frames
F. Giacomini, C. Brukner
preprint arXiv.2012.13754

Falling through masses in superposition: quantum reference frames for indefinite metrics
A.-C. de la Hamette, V. Kabel, E. Castro-Ruiz, Č. Brukner
preprint arXiv.2112.11473

How quantum nonlocality without entanglement witnesses classical processes without causal order
R. Kunjwal, A. Baumeler
preprint arXiv.2202.00440

Algebraic and geometric properties of local transformations
D. Rosset, A. Baumeler, J.-D. Bancal, N. Gisin, A. Martin, M.-O. Renou, Elie Wolfe
preprint arXiv.2004.09405

Complete classification of steerability under local filters and its relation with measurement incompatibility
H.-Y. Ku, C.-Y. Hsieh, S.-L. Chen, Y.-N. Chen, C. Budroni
preprint at arXiv.2201.07691

Quantum Contextuality
C. Budroni, A. Cabello, O. Gühne, M. Kleinmann, J.-Å. Larsson
preprint arXiv.2102.13036

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.