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Testing Whether Gravity Acts as a Quantum Entity When Measured

Farhan Hanif1,*,‡, Debarshi Das1,†,‡, Jonathan Halliwell2, Dipankar Home3, Anupam Mazumdar4, Hendrik Ulbricht5, and Sougato Bose1

  • *Contact author: farhan.hanif.17@ucl.ac.uk
  • †Contact author: debarshi.das@ucl.ac.uk
  • ‡These authors contributed equally to this work.
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Phys. Rev. Lett. 133, 180201 – Published 29 October, 2024

DOI: https://doi.org/10.1103/PhysRevLett.133.180201

Abstract

A defining signature of classical systems is “in principle measurability” without disturbance: a feature manifestly violated by quantum systems. We describe a multi-interferometer experimental setup that can, in principle, reveal the nonclassicality of a spatial superposition-sourced gravitational field if an irreducible disturbance is caused by a measurement of gravity. While one interferometer sources the field, the others are used to measure the gravitational field created by the superposition. This requires neither any specific form of nonclassical gravity, nor the generation of entanglement between any relevant degrees of freedom at any stage, thus distinguishing it from the experiments proposed so far. This test, when added to the recent entanglement-witness based proposals, enlarges the domain of quantum postulates being tested for gravity. Moreover, the proposed test yields a signature of quantum measurement induced disturbance for any finite rate of decoherence, and is device independent.

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References (63)

  1. The Role of Gravitation in Physics: Report from the 1957 Chapel Hill Conference. No. 5 in Max Planck Research Library for the History and Development of Knowledge Sources, edited by C. M. DeWitt, D. Rickles, and J. Renn (Ed. Open Access, Berlin, 2011).
  2. R. Penrose, On gravity’s role in quantum state reduction, Gen. Relativ. Gravit. 28, 581 (1996).
  3. L. Diósi, Models for universal reduction of macroscopic quantum fluctuations, Phys. Rev. A 40, 1165 (1989).
  4. J. Oppenheim and Z. Weller-Davies, The constraints of post-quantum classical gravity, J. High Energy Phys. 02 (2022) 080.
  5. D.-C. Dai, D. Minic, and D. Stojkovic, On black holes as macroscopic quantum objects, Front. Phys. 10, 891977 (2022).
  6. S. Bose, I. Fuentes, A. A. Geraci, S. M. Khan, S. Qvarfort, M. Rademacher, M. Rashid, M. Toro, H. Ulbricht, and C. C. Wanjura, Massive quantum systems as interfaces of quantum mechanics and gravity, arXiv:2311.09218.
  7. S. Bose, K. Jacobs, and P. L. Knight, Scheme to probe the decoherence of a macroscopic object, Phys. Rev. A 59, 3204 (1999).
  8. M. Scala, M. S. Kim, G. W. Morley, P. F. Barker, and S. Bose, Matter-wave interferometry of a levitated thermal nano-oscillator induced and probed by a spin, Phys. Rev. Lett. 111, 180403 (2013).
  9. C. Wan, M. Scala, G. W. Morley, ATM. A. Rahman, H. Ulbricht, J. Bateman, P. F. Barker, S. Bose, and M. S. Kim, Free nano-object Ramsey interferometry for large quantum superpositions, Phys. Rev. Lett. 117, 143003 (2016).
  10. J. S. Pedernales, G. W. Morley, and M. B. Plenio, Motional dynamical decoupling for interferometry with macroscopic particles, Phys. Rev. Lett. 125, 023602 (2020).
  11. R. J. Marshman, A. Mazumdar, R. Folman, and S. Bose, Constructing nano-object quantum superpositions with a Stern-Gerlach interferometer, Phys. Rev. Res. 4, 023087 (2022).
  12. Y. Margalit, O. Dobkowski, Z. Zhou, O. Amit, Y. Japha, S. Moukouri, D. Rohrlich, A. Mazumdar, S. Bose, C. Henkel, and R. Folman, Realization of a complete Stern-Gerlach interferometer: Toward a test of quantum gravity, Sci. Adv. 7, eabg2879 (2021).
  13. R. Zhou, R. J. Marshman, S. Bose, and A. Mazumdar, Catapulting towards massive and large spatial quantum superposition, Phys. Rev. Res. 4, 043157 (2022).
  14. R. Zhou, R. J. Marshman, S. Bose, and A. Mazumdar, Mass-independent scheme for enhancing spatial quantum superpositions, Phys. Rev. A 107, 032212 (2023).
  15. J. F. Donoghue, Introduction to the effective field theory description of gravity, arXiv:gr-qc/9512024.
  16. M. Parikh, F. Wilczek, and G. Zahariade, Signatures of the quantization of gravity at gravitational wave detectors, Phys. Rev. D 104, 046021 (2021).
  17. M. Parikh, F. Wilczek, and G. Zahariade, Quantum mechanics of gravitational waves, Phys. Rev. Lett. 127, 081602 (2021).
  18. G. Tobar, S. K. Manikandan, T. Beitel, and I. Pikovski, Detecting single gravitons with quantum sensing, Nat. Commun. 15, 7229 (2024).
  19. D. Carney, V. Domcke, and N. L. Rodd, Graviton detection and the quantization of gravity, Phys. Rev. D 109, 044009 (2024).
  20. S. Bose, Matter wave ramsey interferometry & the quantum nature of gravity, Available at https://www.youtube.com/watch?v=0Fv-0k13s_k (2016), fundamental Problems of Quantum Physics, ICTS, Bangalore.
  21. S. Bose, A. Mazumdar, G. W. Morley, H. Ulbricht, M. Toroš, M. Paternostro, A. A. Geraci, P. F. Barker, M. S. Kim, and G. Milburn, Spin entanglement witness for quantum gravity, Phys. Rev. Lett. 119, 240401 (2017).
  22. C. Marletto and V. Vedral, Gravitationally induced entanglement between two massive particles is sufficient evidence of quantum effects in gravity, Phys. Rev. Lett. 119, 240402 (2017).
  23. M. Christodoulou and C. Rovelli, On the possibility of laboratory evidence for quantum superposition of geometries, Phys. Lett. B 792, 64 (2019).
  24. R. J. Marshman, A. Mazumdar, and S. Bose, Locality and entanglement in table-top testing of the quantum nature of linearized gravity, Phys. Rev. A 101, 052110 (2020).
  25. S. Bose, A. Mazumdar, M. Schut, and M. Toroš, Mechanism for the quantum natured gravitons to entangle masses, Phys. Rev. D 105, 106028 (2022).
  26. A. Belenchia, R. M. Wald, F. Giacomini, E. Castro-Ruiz, C. Brukner, and M. Aspelmeyer, Quantum superposition of massive objects and the quantization of gravity, Phys. Rev. D 98, 126009 (2018).
  27. D. Carney, Newton, entanglement, and the graviton, Phys. Rev. D 105, 024029 (2022).
  28. D. L. Danielson, G. Satishchandran, and R. M. Wald, Gravitationally mediated entanglement: Newtonian field versus gravitons, Phys. Rev. D 105, 086001 (2022).
  29. T. D. Galley, F. Giacomini, and J. H. Selby, A no-go theorem on the nature of the gravitational field beyond quantum theory, Quantum 6, 779 (2022).
  30. M. Christodoulou, A. Di Biagio, M. Aspelmeyer, C. Brukner, C. Rovelli, and R. Howl, Locally mediated entanglement in linearized quantum gravity, Phys. Rev. Lett. 130, 100202 (2023).
  31. S. Qvarfort, S. Bose, and A. Serafini, Mesoscopic entanglement through central-potential interactions, J. Phys. B 53, 235501 (2020).
  32. T. Krisnanda, T. Paterek, M. Paternostro, and T. C. H. Liew, Quantum neuromorphic approach to efficient sensing of gravity-induced entanglement, Phys. Rev. D 107, 086014 (2023).
  33. D. Carney, H. Müller, and J. M. Taylor, Using an atom interferometer to infer gravitational entanglement generation, PRX Quantum 2, 030330 (2021).
  34. D. Biswas, S. Bose, A. Mazumdar, and M. Toroš, Gravitational optomechanics: Photon-matter entanglement via graviton exchange, Phys. Rev. D 108, 064023 (2023).
  35. S. Etezad-Razavi and L. Hardy, Paradox with phase-coupled interferometers, arXiv:2305.14241.
  36. A. Kent and D. Pitalúa-García, Testing the nonclassicality of spacetime: What can we learn from Bell-Bose –Marletto-Vedral experiments?, Phys. Rev. D 104, 126030 (2021).
  37. M. Schut, J. Tilly, R. J. Marshman, S. Bose, and A. Mazumdar, Improving resilience of quantum-gravity-induced entanglement of masses to decoherence using three superpositions, Phys. Rev. A 105, 032411 (2022).
  38. T. W. van de Kamp, R. J. Marshman, S. Bose, and A. Mazumdar, Quantum gravity witness via entanglement of masses: Casimir screening, Phys. Rev. A 102, 062807 (2020).
  39. S. Rijavec, M. Carlesso, A. Bassi, V. Vedral, and C. Marletto, Decoherence effects in non-classicality tests of gravity, New J. Phys. 23, 043040 (2021).
  40. A. Peres, Separability criterion for density matrices, Phys. Rev. Lett. 77, 1413 (1996).
  41. M. Horodecki, P. Horodecki, and R. Horodecki, Separability of mixed states: Necessary and sufficient conditions, Phys. Lett. A 223, 1 (1996).
  42. See Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevLett.133.180201 for the effect of decoherence in the earlier entanglement witness based proposal, the examples of hybrid models satisfying the NDC, the derivation of the expression of quantum violation of the NDC (in the absence as well as in the presence of decoherence) in the interferometric setup considered by us, the detailed justification for using two probes, estimation of the NDC violations under realistic parameter regimes in the absence or in the presence of decoherence. This Supplemental Material includes Refs. [43,44].
  43. R. Horodecki, P. Horodecki, and M. Horodecki, Violating bell inequality by mixed spin-1/2 states: Necessary and sufficient condition, Phys. Lett. A 200, 340 (1995).
  44. O. Romero-Isart, Quantum superposition of massive objects and collapse models, Phys. Rev. A 84, 052121 (2011).
  45. M. A. Nielsen and I. L. Chuang, Quantum Computation and Quantum Information: 10th Anniversary Edition (Cambridge University Press, Cambridge, England, 2010).
  46. G. Carcassi, L. Maccone, and C. A. Aidala, Four postulates of quantum mechanics are three, Phys. Rev. Lett. 126, 110402 (2021).
  47. A. Steane, https://users.physics.ox.ac.uk/~Steane/teaching/rel_C_fields.pdf, lecture Note (University of Oxford).
  48. A. J. Leggett and A. Garg, Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks?, Phys. Rev. Lett. 54, 857 (1985).
  49. G. C. Knee, K. Kakuyanagi, M.-C. Yeh, Y. Matsuzaki, H. Toida, H. Yamaguchi, S. Saito, A. J. Leggett, and W. J. Munro, A strict experimental test of macroscopic realism in a superconducting flux qubit, Nat. Commun. 7, 13253 (2016).
  50. J. Kofler and C. Brukner, Condition for macroscopic realism beyond the Leggett-Garg inequalities, Phys. Rev. A 87, 052115 (2013).
  51. G. Schild and C. Emary, Maximum violations of the quantum-witness equality, Phys. Rev. A 92, 032101 (2015).
  52. C. Moller, in Les Theories Relativistes de la Gravitation, edited by M. A. Lichnerowicz and M. A. Tonnelat (CNRS, Paris, 1962).
  53. L. Rosenfeld, On quantization of fields, Nucl. Phys. 40, 353 (1963).
  54. D. Kafri, J. Taylor, and G. Milburn, A classical channel model for gravitational decoherence, New J. Phys. 16, 065020 (2014).
  55. L. Diósi and J. J. Halliwell, Coupling classical and quantum variables using continuous quantum measurement theory, Phys. Rev. Lett. 81, 2846 (1998).
  56. D. N. Page and C. D. Geilker, Indirect evidence for quantum gravity, Phys. Rev. Lett. 47, 979 (1981).
  57. R. Colella, A. W. Overhauser, and S. A. Werner, Observation of gravitationally induced quantum interference, Phys. Rev. Lett. 34, 1472 (1975).
  58. M. Schut, A. Geraci, S. Bose, and A. Mazumdar, Micrometer-size spatial superpositions for the QGEM protocol via screening and trapping, Phys. Rev. Res. 6, 013199 (2024).
  59. M. Toroš, T. W. van de Kamp, R. J. Marshman, M. S. Kim, A. Mazumdar, and S. Bose, Relative acceleration noise mitigation for nanocrystal matter-wave interferometry: Applications to entangling masses via quantum gravity, Phys. Rev. Res. 3, 023178 (2021).
  60. M. Bronstein, Republication of: Quantum theory of weak gravitational fields, Gen. Relativ. Gravit. 44, 267283 (2012).
  61. G. Torrieri, The equivalence principle and inertial-gravitational quantum backreaction, Eur. Phys. J. Special Topics 232, 35053517 (2023).

  62. Any decoherence, on the other hand, can be interpreted as a result of the entanglement of the system with the probe and/or wider environment; however this entanglement, while being sufficient, is not necessary for measurement induced state update. Moreover, the system-environment entanglement is generically not verifiable because of the complexity of the environment.

  63. A. Matsumura, Y. Nambu, and K. Yamamoto, Leggett-Garg inequalities for testing quantumness of gravity, Phys. Rev. A 106, 012214 (2022).

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Phys. Rev. Lett. 133, 180201– Published 29 October, 2024
  • Received 19 December 2023
  • Revised 30 July 2024
  • Accepted 11 September 2024
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