Indefinite causal order and quantum coordinates

• URL: http://arxiv.org/abs/2211.15685v3
• Date: Wed, 22 Oct 2025 03:42:56 GMT
• Title: Indefinite causal order and quantum coordinates
• Authors: Anne-Catherine de la Hamette, Viktoria Kabel, Marios Christodoulou, Časlav Brukner,
• Abstract summary: We provide a relativistic definition of causal order between operationally defined events.<n>This observable does not distinguish between the indefinite causal order implemented on an optical bench and the gravitational quantum switch.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Classically the causal order of two timelike separated events A and B is fixed -- either A before B or B before A. This is no longer true in quantum theory, where it is possible to encounter superpositions of causal orders. The quantum switch is one of the most prominent processes with indefinite causal order. Optical realizations of the quantum switch have been successfully implemented in experiments, but, some argue this merely simulates a process with indefinite causal order and that a superposition of spacetime metrics is required for a true realization. Here, we provide a relativistic definition of causal order between operationally defined events that defines a meaningful observable in both the general relativistic and quantum mechanical sense. Importantly, this observable does not distinguish between the indefinite causal order implemented on an optical bench and the gravitational quantum switch, a gedankenexperiment where the indefinite causal order is achieved by a quantum superposition of gravitational fields. Therefore, our results support the thesis that the optical quantum switch is just as much a realization of indefinite causal order as its gravitational counterpart, which makes use of the quantum mechanical behavior of spacetime.

Related papers

• Time Symmetry, Retrocausality, and Emergent Collapse: The Tlalpan Interpretation of Quantum Mechanics [51.56484100374058]
  The Tlalpan Interpretation (QTI) proposes that the wavefunction collapse is not a primitive, axiomatic rule but an emergent phenomenon.<n>The novelty of QTI lies in its embedding of collapse within the conceptual language of critical phenomena in statistical physics.
  arXiv  Detail & Related papers  (2025-08-25T20:30:56Z)
• Emergence of cosmic structure from Planckian discreteness [47.03992469282679]
  In the standard paradigm the inhomogeneities observed in the CMB arise from quantum fluctuations of an initially homogeneous and isotropic vacuum state.<n>We propose an alternative paradigm in which such inhomogeneities are present from the very beginning.<n>Specifically, inhomogeneities in the quantum state at the Planck scale propagate into semiclassical inhomogeneities on CMB scales.
  arXiv  Detail & Related papers  (2025-06-18T12:33:31Z)
• Kochen-Specker for many qubits and the classical limit [55.2480439325792]
  It is shown that quantum and classical predictions converge as the number of qubits is increases to the macroscopic scale. This way to explain the classical limit concurs with, and improves, a result previously reported for GHZ states.
  arXiv  Detail & Related papers  (2024-11-26T22:30:58Z)
• Realizing fracton order from long-range quantum entanglement in programmable Rydberg atom arrays [45.19832622389592]
  Storing quantum information requires battling quantum decoherence, which results in a loss of information over time. To achieve error-resistant quantum memory, one would like to store the information in a quantum superposition of degenerate states engineered in such a way that local sources of noise cannot change one state into another. We show that this platform also allows to detect and correct certain types of errors en route to the goal of true error-resistant quantum memory.
  arXiv  Detail & Related papers  (2024-07-08T12:46:08Z)
• Possibilistic and maximal indefinite causal order in the quantum switch [0.0]
  We show that the indefinite causal order in the quantum switch can be certified device-independently when assuming the impossibility of superluminal influences. We also show that the observed correlations are incompatible even with the existence of a causal order on only a small fraction of the runs of the experiment.
  arXiv  Detail & Related papers  (2023-11-01T14:55:03Z)
• Indefinite order in the interface of quantum mechanics and gravity [0.0]
  We discuss the notion of indefinite order, which first appears in an abstract generalization of Quantum Theory. We present how scenarios involving gravity in low energies could lead to indefinite order.
  arXiv  Detail & Related papers  (2023-10-03T01:16:27Z)
• Quantum Discord Witness with Uncharacterized Devices [18.751513188036334]
  We propose a new approach using uncharacterized measurements to witness quantum discord of an unknown bipartite state within arbitrary dimension system. The feature of high robustness against device imperfections, such as loss-tolerance and error-tolerance, shows our method is experimentally feasible.
  arXiv  Detail & Related papers  (2023-03-20T14:51:53Z)
• Coherent control of a high-orbital hole in a semiconductor quantum dot [21.05348937863074]
  coherent manipulation of single charge carriers in quantum dots is limited mainly to their lowest orbital states. We demonstrate an all-optical method to control high-orbital states of a hole via stimulated Auger process. Our work opens new possibilities for understanding the fundamental properties of high-orbital states in quantum emitters.
  arXiv  Detail & Related papers  (2022-12-21T03:49:46Z)
• Experimental superposition of time directions [0.5018974919510384]
  We consider quantum processes probed in a coherent superposition of forwards and backwards time directions. This yields a broader class of quantum processes than the ones considered so far in the literature. We demonstrate for the first time an operation belonging to this new class: the quantum time flip.
  arXiv  Detail & Related papers  (2022-11-02T17:05:49Z)
• Quantum Instability [30.674987397533997]
  We show how a time-independent, finite-dimensional quantum system can give rise to a linear instability corresponding to that in the classical system. An unstable quantum system has a richer spectrum and a much longer recurrence time than a stable quantum system.
  arXiv  Detail & Related papers  (2022-08-05T19:53:46Z)
• Quantum dynamics corresponding to chaotic BKL scenario [62.997667081978825]
  Quantization smears the gravitational singularity avoiding its localization in the configuration space. Results suggest that the generic singularity of general relativity can be avoided at quantum level.
  arXiv  Detail & Related papers  (2022-04-24T13:32:45Z)
• No-signalling constrains quantum computation with indefinite causal structure [45.279573215172285]
  We develop a formalism for quantum computation with indefinite causal structures. We characterize the computational structure of higher order quantum maps. We prove that these rules, which have a computational and information-theoretic nature, are determined by the more physical notion of the signalling relations between the quantum systems.
  arXiv  Detail & Related papers  (2022-02-21T13:43:50Z)
• Interactive Protocols for Classically-Verifiable Quantum Advantage [46.093185827838035]
  "Interactions" between a prover and a verifier can bridge the gap between verifiability and implementation. We demonstrate the first implementation of an interactive quantum advantage protocol, using an ion trap quantum computer.
  arXiv  Detail & Related papers  (2021-12-09T19:00:00Z)
• 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)
• Quantum chicken-egg dilemmas: Delayed-choice causal order and the reality of causal non-separability [0.0]
  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.
  arXiv  Detail & Related papers  (2020-08-18T12:03:31Z)
• Operational Resource Theory of Imaginarity [48.7576911714538]
  We show that quantum states are easier to create and manipulate if they only have real elements. As an application, we show that imaginarity plays a crucial role for state discrimination.
  arXiv  Detail & Related papers  (2020-07-29T14:03:38Z)
• Projection evolution and quantum spacetime [68.8204255655161]
  We discuss the problem of time in quantum mechanics. An idea of construction of a quantum spacetime as a special set of the allowed states is presented. An example of a structureless quantum Minkowski-like spacetime is also considered.
  arXiv  Detail & Related papers  (2019-10-24T14:54:11Z)

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.