Experimental violation of a Bell-like inequality for causal order

• URL: http://arxiv.org/abs/2506.20516v1
• Date: Wed, 25 Jun 2025 15:04:13 GMT
• Title: Experimental violation of a Bell-like inequality for causal order
• Authors: Yu Guo, Hao Tang, Xiao-Min Hu, Yun-Feng Huang, Chuan-Feng Liu, Guang-Can Guo, Giulio Chiribella, Bi-Heng Liu,
• Abstract summary: Indefinite causal order provides a resource for quantum information processing.<n>We report the experimental violation of a Bell-like inequality for causal order using a photonic setup.
• Score: 7.0149746383755325
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum mechanics allows for coherent control over the order in which different processes take place on a target system, giving rise to a new feature known as indefinite causal order. Indefinite causal order provides a resource for quantum information processing, and can be in principle be detected by the violation of certain inequalities on the correlations between measurement outcomes observed in the laboratory, in a similar way as quantum nonlocality can be detected by the violation of Bell inequalities. Here we report the experimental violation of a Bell-like inequality for causal order using a photonic setup where the order of two optical processes is controlled by a single photon of a polarization-entangled photon pair. Our proof-of-principle demonstration overcomes major technical challenges, including the need of high-speed quantum operations in photonic time-bin encoding, nanosecond synchronization of active optical and electronic elements to meet the target required for spacelike separation, and active temperature stabilization of a Mach-Zehnder interferometer to ensure statistically significant violations. These experimental advances enable a statistically significant violation of the causal inequality, and open up a path towards a device-independent certification of indefinite order of events with uncharacterized quantum devices.

Related papers

• Experimental device-independent certification of indefinite causal order [9.01526727292497]
  We report an experimental verification of the causal inequality using spacelike-separated entangled photons.<n>Our results pave the way toward a complete understanding of indefinite causal order and its potential applications in quantum information processing.
  arXiv  Detail & Related papers  (2025-08-06T17:07:59Z)
• Anticipating Decoherence: a Predictive Framework for Enhancing Coherence in Quantum Emitters [96.41185946460115]
  We develop an anticipatory framework for forecasting and decoherence engineering in remote quantum emitters.<n>We show that a machine learning model trained on limited data can accurately forecast unseen spectral behavior.<n>These results pave the way for real-time decoherence engineering in scalable quantum systems.
  arXiv  Detail & Related papers  (2025-08-04T17:23:14Z)
• Optimizing the quantum interference between single photons and local oscillator with photon correlations [0.0]
  We report on two homodyne photon-correlation techniques enabling the precise measurement of the overlap between a single photon generated by a quantum dot-cavity device and pulsed laser light.<n>The different statistics of interfering fields lead to specific signatures of the quantum interference on the photon correlations at the output of the interfering beam splitter.<n>We compare the behavior of maximized overlap, measuring either the Hong-Ou-Mandel visibility between both outputs or the photon bunching at a single output.
  arXiv  Detail & Related papers  (2025-04-16T14:19:51Z)
• Strong coupling between a single photon and a photon pair [43.14346227009377]
  We report an experimental observation of the strong coupling between a single photon and a photon pair in an ultrastrongly-coupled circuit-QED system. Results represent a key step towards a new regime of quantum nonlinear optics.
  arXiv  Detail & Related papers  (2024-01-05T10:23:14Z)
• Limits for coherent optical control of quantum emitters in layered materials [49.596352607801784]
  coherent control of a two-level system is among the most essential challenges in modern quantum optics. We use a mechanically isolated quantum emitter in hexagonal boron nitride to explore the individual mechanisms which affect the coherence of an optical transition under resonant drive. New insights on the underlying physical decoherence mechanisms reveals a limit in temperature until which coherent driving of the system is possible.
  arXiv  Detail & Related papers  (2023-12-18T10:37:06Z)
• Violation of Bell inequality by photon scattering on a two-level emitter [4.810881229568956]
  Entanglement, the non-local correlations present in quantum systems, is a curious feature of quantum mechanics and the fuel of quantum technology. We show how a single two-level emitter deterministically coupled to light in a nanophotonic waveguide is used to realize genuine photonic quantum entanglement for excitation at the single photon level.
  arXiv  Detail & Related papers  (2023-06-22T11:01:24Z)
• Coherently excited nonlocal quantum features using polarization-frequency correlation between quantum erasers [0.0]
  Photon indistinguishability is an essential concept to understanding mysterious quantum features from the viewpoint of the wave-particle duality in quantum mechanics. Here, a pure coherence approach is applied for the nonlocal correlation based on the polarization-frequency correlation of Poisson-distributed coherent photon pairs.
  arXiv  Detail & Related papers  (2023-04-08T13:38:24Z)
• On-chip quantum information processing with distinguishable photons [55.41644538483948]
  Multi-photon interference is at the heart of photonic quantum technologies. Here, we experimentally demonstrate that detection can be implemented with a temporal resolution sufficient to interfere photons detuned on the scales necessary for cavity-based integrated photon sources. We show how time-resolved detection of non-ideal photons can be used to improve the fidelity of an entangling operation and to mitigate the reduction of computational complexity in boson sampling experiments.
  arXiv  Detail & Related papers  (2022-10-14T18:16:49Z)
• Coherence interpretation of the noninterfering Sagnac-based quantum correlation [0.0]
  Bell inequality violation is a quantitative measurement tool for quantum entanglement. Here, the role of coincidence detection is coherently investigated for the nonlocal correlation in a simple polarization-basis selective non-interferometric system.
  arXiv  Detail & Related papers  (2022-06-10T21:16:24Z)
• Experimental violations of Leggett-Garg's inequalities on a quantum computer [77.34726150561087]
  We experimentally observe the violations of Leggett-Garg-Bell's inequalities on single and multi-qubit systems. Our analysis highlights the limits of nowadays quantum platforms, showing that the above-mentioned correlation functions deviate from theoretical prediction as the number of qubits and the depth of the circuit grow.
  arXiv  Detail & Related papers  (2021-09-06T14:35:15Z)
• Coherence in Cooperative Photon Emission from Indistinguishable Quantum Emitters [0.0]
  We probe the role of coherence in cooperative emission arising from two distant but indistinguishable solid-state emitters because of path erasure. Our experiments establish techniques to control and characterize cooperative behavior between matter qubits using the full quantum optics toolbox.
  arXiv  Detail & Related papers  (2021-05-19T20:59:25Z)
• Observation-dependent suppression and enhancement of two-photon coincidences by tailored losses [68.8204255655161]
  Hong-Ou-Mandel (HOM) effect can lead to a perfect suppression of two-particle coincidences between the output ports of a balanced beam splitter. In this work, we demonstrate experimentally that the two-particle coincidence statistics of two bosons can instead be seamlessly tuned to substantial enhancement. Our findings reveal a new approach to harnessing non-Hermitian settings for the manipulation of multi-particle quantum states.
  arXiv  Detail & Related papers  (2021-05-12T06:47:35Z)
• Coherently controlled quantum features in a coupled interferometric scheme [0.0]
  In an interferometric scheme, anticorrelation results from photon bunching based on randomness when entangled photon pairs impinge on a beam splitter. In this paper, the origin of quantum features in a coupled interferometric scheme is investigated using pure coherence optics. A deterministic method of entangled photon-pair generation is proposed for on-demand coherence control of quantum processing.
  arXiv  Detail & Related papers  (2021-02-18T07:10:32Z)
• Enhancing nonclassical bosonic correlations in a Quantum Walk network through experimental control of disorder [50.591267188664666]
  We experimentally realize a controllable inhomogenous Quantum Walk dynamics. We observe two photon states which exhibit an enhancement in the quantum correlations between two modes of the network.
  arXiv  Detail & Related papers  (2021-02-09T10:57:00Z)
• Einselection from incompatible decoherence channels [62.997667081978825]
  We analyze an open quantum dynamics inspired by CQED experiments with two non-commuting Lindblad operators. We show that Fock states remain the most robust states to decoherence up to a critical coupling.
  arXiv  Detail & Related papers  (2020-01-29T14:15:19Z)

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.