Experimental aspects of indefinite causal order in quantum mechanics

LA Rozema, T Strömberg, H Cao, Y Guo, BH Liu… - Nature Reviews …, 2024 - nature.com
In the past decade, the toolkit of quantum information has been expanded to include
processes in which the basic operations do not have definite causal relations. Originally …

Experiments on quantum causality

K Goswami, J Romero - AVS Quantum Science, 2020 - pubs.aip.org
Quantum causality extends the conventional notion of the fixed causal structure by allowing
channels and operations to act in an indefinite causal order. The importance of such an …

Experimental quantum communication enhancement by superposing trajectories

G Rubino, LA Rozema, D Ebler, H Kristjánsson… - Physical Review …, 2021 - APS
In quantum communication networks, wires represent well-defined trajectories along which
quantum systems are transmitted. In spite of this, trajectories can be used as a quantum …

Cyclic quantum causal models

J Barrett, R Lorenz, O Oreshkov - Nature communications, 2021 - nature.com
Causal reasoning is essential to science, yet quantum theory challenges it. Quantum
correlations violating Bell inequalities defy satisfactory causal explanations within the …

Embedding cyclic causal structures in acyclic spacetimes: no-go results for process matrices

V Vilasini, R Renner - arxiv, 2022 - research-collection.ethz.ch
Causality can be defined in terms of a space-time structure or based on information-theoretic
structures, which correspond to very different notions of causation. When analysing physical …

Embedding cyclic information-theoretic structures in acyclic space-times: No-go results for indefinite causality

V Vilasini, R Renner - Physical Review A, 2024 - APS
The notions of causality adopted within the quantum information and space-time physics
communities are distinct. Although experience tells us that these notions play together in a …

Computational advantage from the quantum superposition of multiple temporal orders of photonic gates

MM Taddei, J Cariñe, D Martínez, T García, N Guerrero… - PRX Quantum, 2021 - APS
Models for quantum computation with circuit connections subject to the quantum
superposition principle have recently been proposed. In them, a control quantum system can …

Time-delocalized quantum subsystems and operations: on the existence of processes with indefinite causal structure in quantum mechanics

O Oreshkov - Quantum, 2019 - quantum-journal.org
It has been shown that it is theoretically possible for there to exist higher-order quantum
processes in which the operations performed by separate parties cannot be ascribed a …

Computational advantage from a quantum superposition of qubit gate orders

MJ Renner, Č Brukner - Physical Review Letters, 2022 - APS
In an ordinary quantum algorithm the gates are applied in a fixed order on the systems. The
introduction of indefinite causal structures allows us to relax this constraint and control the …

Quantum theory cannot violate a causal inequality

T Purves, AJ Short - Physical Review Letters, 2021 - APS
Within quantum theory, we can create superpositions of different causal orders of events,
and observe interference between them. This raises the question of whether quantum theory …