Quantum chicken-egg dilemmas: Delayed-choice causal order and the reality of causal non-separability

• URL: http://arxiv.org/abs/2008.07876v2
• Date: Mon, 10 May 2021 09:14:46 GMT
• Title: Quantum chicken-egg dilemmas: Delayed-choice causal order and the reality of causal non-separability
• Authors: Simon Milz, Dominic Jurkschat, Felix A. Pollock, and Kavan Modi
• Abstract summary: We show that causally indefinite processes can be realised with schemes where C serves only as a classical flag. We demonstrate that quantum mechanics allows for phenomena where C can deterministically decide whether A comes before B or vice versa.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Recent frameworks describing quantum mechanics in the absence of a global causal order admit the existence of causally indefinite processes, where it is impossible to ascribe causal order for events A and B. These frameworks even allow for processes that violate the so-called causal inequalities, which are analogous to Bell's inequalities. However, the physicality of these exotic processes is, in the general case, still under debate, bringing into question their foundational relevance. While it is known that causally indefinite processes can be probabilistically realised by means of a quantum circuit, along with an additional conditioning event C, concrete insights into the ontological meaning of such implementation schemes have heretofore been limited. Here, we show that causally indefinite processes can be realised with schemes where C serves only as a classical flag heralding which causally indefinite process was realised. We then show that there are processes where any pure conditioning measurement of C leads to a causally indefinite process for A and B, thus establishing causal indefiniteness as a basis-independent quantity. Finally, we demonstrate that quantum mechanics allows for phenomena where C can deterministically decide whether A comes before B or vice versa, without signalling to either. This is akin to Wheeler's famous delayed-choice experiment establishing definite causal order in quantum mechanics as instrument-\textit{dependent} property.

Related papers

• Proposal of an optical Bell's experiment to test the boundary between determinism and indeterminism in Quantum Mechanics [41.94295877935867]
  It was recently noted the existence of an apparently discontinuous boundary between determinism and indeterminism in Quantum Mechanics. We propose to explore this boundary by recording the distribution of outcomes of a given parity interrupted by outcomes of the other parity. The features of these distributions for small rotations of the angle settings near critical points may indicate whether the underlying process is in-deterministic or not.
  arXiv  Detail & Related papers  (2024-08-20T14:48:08Z)
• A de Finetti theorem for quantum causal structures [0.0]
  Similar questions for classical probabilities, quantum states, and quantum channels are beautifully answered by so-called "de Finetti theorems" We extend the result to processes with arbitrary causal structure, including indefinite causal order and multi-time, non-Markovian processes applicable to noisy quantum devices.
  arXiv  Detail & Related papers  (2024-03-15T14:00:59Z)
• Reassessing the advantage of indefinite causal orders for quantum metrology [0.0]
  In this work, we argue that some of these advantages in fact do not hold if a fairer comparison is made. We consider a framework that allows for a proper comparison between the performance of different classes of indefinite causal order processes.
  arXiv  Detail & Related papers  (2023-12-19T14:03:40Z)
• A Measure-Theoretic Axiomatisation of Causality [55.6970314129444]
  We argue in favour of taking Kolmogorov's measure-theoretic axiomatisation of probability as the starting point towards an axiomatisation of causality. Our proposed framework is rigorously grounded in measure theory, but it also sheds light on long-standing limitations of existing frameworks.
  arXiv  Detail & Related papers  (2023-05-19T13:15:48Z)
• Universality of critical dynamics with finite entanglement [68.8204255655161]
  We study how low-energy dynamics of quantum systems near criticality are modified by finite entanglement. Our result establishes the precise role played by entanglement in time-dependent critical phenomena.
  arXiv  Detail & Related papers  (2023-01-23T19:23:54Z)
• Quantum diffeomorphisms cannot make indefinite causal order definite [0.0]
  We provide a relativistic definition of causal order, show that it encompasses both the optical and gravitational quantum switch, and does not differentiate between them. Importantly, this observable does not distinguish between the indefinite causal order implemented in the optical and gravitational quantum switch, thus supporting the thesis that the optical quantum switch is just as much a realization of indefinite causal order as its gravitational counterpart.
  arXiv  Detail & Related papers  (2022-11-28T19:00:01Z)
• Existence of processes violating causal inequalities on time-delocalised subsystems [0.0]
  It is possible to exist quantum and classical processes in which the operations performed by separate parties do not occur in a well-defined causal order. We show that realisations on time-delocalised subsystems exist for all unitary extensions of tripartite processes.
  arXiv  Detail & Related papers  (2022-01-27T22:34:02Z)
• Unification of Random Dynamical Decoupling and the Quantum Zeno Effect [68.8204255655161]
  We show that the system dynamics under random dynamical decoupling converges to a unitary with a decoupling error that characteristically depends on the convergence speed of the Zeno limit. This reveals a unification of the random dynamical decoupling and the quantum Zeno effect.
  arXiv  Detail & Related papers  (2021-12-08T11:41:38Z)
• Experiments on quantum causality [0.0]
  Quantum causality extends the conventional notion of fixed causal structure by allowing channels and operations to act in an indefinite causal order. In this review, we will walk through the basic theory of indefinite causal order and focus on experiments that rely on a physically realisable indefinite causal ordered process.
  arXiv  Detail & Related papers  (2020-09-01T15:25:26Z)
• Bell's theorem for trajectories [62.997667081978825]
  A trajectory is not an outcome of a quantum measurement, in the sense that there is no observable associated with it. We show how to overcome this problem by considering a special case of our generic inequality that can be experimentally tested point-by-point in time.
  arXiv  Detail & Related papers  (2020-01-03T01:40:44Z)
• Quantum-secure message authentication via blind-unforgeability [74.7729810207187]
  We propose a natural definition of unforgeability against quantum adversaries called blind unforgeability. This notion defines a function to be predictable if there exists an adversary who can use "partially blinded" access to predict values. We show the suitability of blind unforgeability for supporting canonical constructions and reductions.
  arXiv  Detail & Related papers  (2018-03-10T05:31:38Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.