Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Testing foundations of quantum mechanics with photons

Nature Physics volume 10, pages 278–286 (2014)Cite this article

Subjects

Abstract

Quantum mechanics continues to predict effects at odds with a classical understanding of nature. Experiments with light at the single-photon level have historically been at the forefront of fundamental tests of quantum theory and the current developments in photonic technologies enable the exploration of new directions. Here we review recent photonic experiments to test two important themes in quantum mechanics: wave–particle duality, which is central to complementarity and delayed-choice experiments; and Bell nonlocality, where the latest theoretical and technological advances have allowed all controversial loopholes to be separately addressed in different experiments.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Delayed-choice experimental set-ups.
Figure 2: A nonlocality experiment and associated loopholes.
Figure 3: Experiments for closing the Bell nonlocality loopholes.
Figure 4: EPR steering.

References

  1. Tonomura, A., Endo, J., Matsuda, T., Kawasaki, T. & Ezawa, H. Demonstration of single-electron buildup of an interference pattern. Am. J. Phys. 57, 117–120 (1989).

    ADS  Google Scholar 

  2. Bach, R., Pope, D., Liou, S.-H. & Batelaan, H. Controlled double-slit electron diffraction. New J. Phys. 15, 033018 (2013).

    ADS  Google Scholar 

  3. Jönsson, C. Electron diffraction at multiple slits. Am. J. Phys. 42, 4–11 (1974).

    ADS  Google Scholar 

  4. Carnal, O. & Mlynek, J. Young's double-slit experiment with atoms: A simple atom interferometer. Phys. Rev. Lett. 66, 2689–2692 (1991).

    ADS  Google Scholar 

  5. Arndt, M. et al. Wave–particle duality of C60 molecules. Nature 401, 680–682 (1999).

    ADS  Google Scholar 

  6. Taylor, G. I. Interference fringes with feeble light. Proc. Camb. Phil. Soc. 15, 114–115 (1909).

    Google Scholar 

  7. Clauser, J. F. Experimental distinction between the quantum and classical field-theoretic predictions for the photoelectric effect. Phys. Rev. D 9, 853–860 (1974).

    ADS  Google Scholar 

  8. Grangier, P., Roger, G. & Aspect, A. Experimental evidence for a photon anticorrelation effect on a beam splitter: A new light on single-photon interferences. Europhys. Lett. 1, 173 (1986).

    ADS  Google Scholar 

  9. Jammer, M. The Philosophy of Quantum Mechanics (Wiley, 1974).

    Google Scholar 

  10. Guerreiro, T., Sanguinetti, B., Zbinden, H., Gisin, N. & Suarez, A. Single-photon space-like antibunching. Preprint at http://arxiv.org/quant-ph/1204.1712 (2012).

  11. Hall, M. J. W. Prior information: How to circumvent the standard joint-measurement uncertainty relation. Phys. Rev. A 69, 052113 (2004).

    ADS  MathSciNet  Google Scholar 

  12. Ozawa, M. Universally valid reformulation of the Heisenberg uncertainty principle on noise and disturbance in measurement. Phys. Rev. A 67, 042105 (2003).

    ADS  Google Scholar 

  13. Erhart, J. et al. Experimental demonstration of a universally valid error-disturbance uncertainty relation in spin measurements. Nature Phys. 8, 185–189 (2012).

    ADS  Google Scholar 

  14. Weston, M. M., Hall, M. J. W., Palsson, M. S., Wiseman, H. M. & Pryde, G. J. Experimental test of universal complementarity relations. Phys. Rev. Lett. 110, 220402 (2013).

    ADS  Google Scholar 

  15. Wiseman, H. M. Grounding Bohmian mechanics in weak values and Bayesianism. New J. Phys. 9, 165 (2007).

    ADS  Google Scholar 

  16. Kocsis, S. et al. Observing the average trajectories of single photons in a two-slit interferometer. Science 332, 1170–1173 (2011).

    ADS  MATH  Google Scholar 

  17. Aharonov, Y., Albert, D. & Vaidman, L. How the result of a measurement of a component of the spin of a spin-1/2 particle can turn out to be 100. Phys. Rev. Lett. 60, 1351–1354 (1988).

    ADS  Google Scholar 

  18. Wheeler, J. A. in Mathematical Foundations of Quantum Theory (ed. Marlow, A. R.) 9–48 (Academic Press, 1978).

    Google Scholar 

  19. Wheeler, J. A. & Zurek, W. H. Quantum Theory and Measurement (Princeton Univ. Press, 1984).

    Google Scholar 

  20. Alley, C. O., Jacubowicz, O. G. & Wickes, W. C. in Proc. Second Int. Symp.Foundations of Quantum Mechanics (Narani, H. ed.) 36 (Physics Society of Japan, 1987).

    Google Scholar 

  21. Hellmuth, T., Walther, H., Zajonc, A. & Schleich, W. Delayed-choice experiments in quantum interference. Phys. Rev. A 35, 2532–2541 (1987).

    ADS  Google Scholar 

  22. Lawson-Daku, B. J. et al. Delayed choices in atom Stern–Gerlach interferometry. Phys. Rev. A 54, 5042–5047 (1996).

    ADS  Google Scholar 

  23. Kim, Y-H., Yu, R., Kulik, S. P., Shih, Y. & Scully, M. O. Delayed “choice” quantum eraser. Phys. Rev. Lett. 84, 1–5 (2000).

    ADS  Google Scholar 

  24. Jacques, V. et al. Experimental realization of Wheeler's delayed-choice gedanken experiment. Science 315, 966–968 (2007).

    ADS  Google Scholar 

  25. Jacques, V. et al. Illustration of quantum complementarity using single photons interfering on a grating. New J. Phys. 10, 123009 (2008).

    ADS  Google Scholar 

  26. Afshar, S. S. Violation of the principle of complementarity, and its implications. Proc. SPIE 5866, 229–244 (2005).

    ADS  Google Scholar 

  27. Afshar, S. S., Flores, E., McDonald, K. F. & Knoesel, E. Paradox in wave–particle duality. Found. Phys. 37, 295–305 (2007).

    ADS  MathSciNet  MATH  Google Scholar 

  28. Ionicioiu, R. & Terno, D. R. Proposal for a quantum delayed-choice experiment. Phys. Rev. Lett. 107, 230406 (2011).

    ADS  Google Scholar 

  29. Kaiser, F., Coudreau, T., Milman, P., Ostrowsky, D. B. & Tanzilli, S. Entanglement-enabled delayed-choice experiment. Science 338, 637–640 (2012).

    ADS  Google Scholar 

  30. Peruzzo, A., Shadbolt, P., Brunner, N., Popescu, S. & O'Brien, J. L. A quantum delayed-choice experiment. Science 338, 634–637 (2012).

    ADS  Google Scholar 

  31. Roy, S. S., Shukla, A. & Mahesh, T. S. NMR implementation of a quantum delayed-choice experiment. Phys. Rev. A 85, 022109 (2012).

    ADS  Google Scholar 

  32. Politi, A., Matthews, J. C. F., Thompson, M. G. & O'Brien, J. L. Integrated Quantum Photonics. IEEE J. Select. Top. Quant, Electron, 15, 1673–1684 (2009).

    ADS  Google Scholar 

  33. Shadbolt, P. J. et al. Generating, manipulating and measuring entanglement and mixture with a reconfigurable photonic circuit. Nature Photon. 6, 45–49 (2012).

    ADS  Google Scholar 

  34. Clauser, J. F., Horne, M. A., Shimony, A. & Holt, R. A. Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett. 23, 880–884 (1969).

    ADS  MATH  Google Scholar 

  35. Scully, M. O. & Drühl, K. Quantum eraser: A proposed photon correlation experiment concerning observation and “delayed choice” in quantum mechanics. Phys. Rev. A 25, 2208–2213 (1982).

    ADS  Google Scholar 

  36. Ma, X-S. et al. Quantum erasure with causally disconnected choice. Proc. Natl Acad. Sci. USA 110, 1221–1226 (2013).

    ADS  Google Scholar 

  37. Kochen, S. & Specker, E. P. The problem of hidden variables in quantum mechanics. J. Math. Mech. 17, 59–87 (1967).

    MathSciNet  MATH  Google Scholar 

  38. Cabello, A. & García-Alcaine, G. Proposed experimental tests of the Bell–Kochen–Specker theorem. Phys. Rev. Lett. 80, 1797–1799 (1998).

    ADS  MATH  Google Scholar 

  39. Meyer, D. A. Finite precision measurement nullifies the Kochen–Specker theorem. Phys. Rev. Lett. 83, 3751–3754 (1999).

    ADS  MathSciNet  MATH  Google Scholar 

  40. Greenberger, D., Horne, M., Shimony, A. & Zeilinger, A. Bell's theorem without inequalities. Am. J. Phys 58, 1131–1143 (1990).

    ADS  MathSciNet  MATH  Google Scholar 

  41. Simon, C., Zukowski, M., Weinfurter, H. & Zeilinger, A. Feasible “Kochen–Specker” experiment with single particles. Phys. Rev. Lett. 85, 1783–1786 (2000).

    ADS  MathSciNet  MATH  Google Scholar 

  42. Cabello, A. “All versus nothing” inseparability for two observers. Phys. Rev. Lett. 87, 010403 (2001).

    ADS  Google Scholar 

  43. Amselem, E., Rådmark, M., Bourennane, M. & Cabello, A. State-independent quantum contextuality with single photons. Phys. Rev. Lett. 103, 160405 (2009).

    ADS  Google Scholar 

  44. Michler, M., Weinfurter, H. & Zukowski, M. Experiments towards falsification of noncontextual hidden variable theories. Phys. Rev. Lett. 84, 5457–5461 (2000).

    ADS  Google Scholar 

  45. Huang, Y-F., Li, C-F., Zhang, Y-S., Pan, J-W. & Guo, G-C. Experimental test of the Kochen–Specker theorem with single photons. Phys. Rev. Lett. 90, 250401 (2003).

    ADS  Google Scholar 

  46. Lapkiewicz, R. et al. Experimental non-classicality of an indivisible quantum system. Nature 474, 490–493 (2011).

    Google Scholar 

  47. Klyachko, A. A., Can, M. A., Binicioğlu, S. & Shumovsky, A. S. Simple test for hidden variables in spin-1 systems. Phys. Rev. Lett. 101, 020403 (2008).

    ADS  MathSciNet  MATH  Google Scholar 

  48. Abrams, D. S. & Lloyd, S. Nonlinear quantum mechanics implies polynomial-time solution for NP-complete and #P problems. Phys. Rev. Lett. 81, 3992–3995 (1998).

    ADS  Google Scholar 

  49. Sinha, U., Couteau, C., Jennewein, T., Laflamme, R. & Weihs, G. Ruling out multi-order interference in quantum mechanics. Science 329, 418–421 (2010).

    ADS  MathSciNet  MATH  Google Scholar 

  50. Bell, J. S. On the Einstein Podolsky Rosen paradox. Physics 1, 195–200 (1964).

    MathSciNet  Google Scholar 

  51. Pan, J-W. et al. Multiphoton entanglement and interferometry. Rev. Mod. Phys. 84, 777–838 (2012).

    ADS  Google Scholar 

  52. Brunner, N., Cavalcanti, D., Pironio, S., Scarani, V. & Wehner, S. Bell nonlocality. Rev. Mod. Phys. (in the press); preprint at http://arxiv.org/quant-ph/1303.2849 (2013).

  53. Freedman, S. J. & Clauser, J. F. Experimental test of local hidden-variable theories. Phys. Rev. Lett. 28, 938–941 (1972).

    ADS  Google Scholar 

  54. Aspect, A., Grangier, P. & Roger, G. Experimental realization of Einstein–Podolsky–Rosen–Bohm Gedankenexperiment: A new violation of Bell's inequalities. Phys. Rev. Lett. 49, 91–94 (1982).

    ADS  Google Scholar 

  55. Tasca, D. S., Walborn, S. P., Toscano, F. & Souto Ribeiro, P. H. Observation of tunable Popescu–Rohrlich correlations through postselection of a Gaussian state. Phys. Rev. A 80, 030101(R) (2009).

    ADS  Google Scholar 

  56. Gerhardt, I. et al. Experimentally faking the violation of Bell's inequalities. Phys. Rev. Lett. 107, 170404 (2011).

    ADS  Google Scholar 

  57. Pomarico, E., Sanguinetti, B., Sekatski, P., Zbinden, H. & Gisin, N. Experimental amplification of an entangled photon: what if the detection loophole is ignored? New J. Phys. 13, 063031 (2011).

    ADS  Google Scholar 

  58. Eberhard, P. H. Background level and counter efficiencies required for a loophole-free Einstein–Podolsky–Rosen experiment. Phys. Rev. A 47, 747–750 (1993).

    ADS  Google Scholar 

  59. Giustina, M. et al. Bell violation using entangled photons without the fair-sampling assumption. Nature 497, 227–230 (2013).

    ADS  Google Scholar 

  60. Christensen, B. G. et al. Detection-loophole-free test of quantum nonlocality, and applications. Phys. Rev. Lett. 111, 130406 (2013).

    ADS  Google Scholar 

  61. Lita, A. E., Miller, A. & Nam, S. W. Counting nearinfrared single-photons with 95% efficiency. Opt. Express 16, 3032 (2008).

    ADS  Google Scholar 

  62. Kim, R., Fiorentino, M. & Wong, F. Phase-stable source of polarization entangled photons using a Sagnac interferometer. Phys. Rev. A 73, 12316 (2006).

    ADS  Google Scholar 

  63. Fedrizzi, A., Herbst, T., Poppe, A., Jennewein, T. & Zeilinger, A. A wavelength tunable fibre-coupled source of narrowband entangled photons. Opt. Express 15, 15377–15386 (2007).

    ADS  Google Scholar 

  64. Larsson, J-A. & Gill, R. D. Bell's inequality and the coincidence-time loophole. Europhys. Lett. 67, 707–713 (2004).

    ADS  MATH  Google Scholar 

  65. Kofler, J., Ramelow, S., Giustina, M. & Zeilinger, A. On 'Bell violation using entangled photons without the fairsampling assumption'. Preprint at http://arxiv.org/abs/1307.6475 (2013).

  66. Aspect, A., Dalibard, J. & Roger, G. Experimental test of Bell's inequalities using time-varying analyzers. Phys.Rev. Lett. 49, 1804–1807 (1982).

    ADS  MathSciNet  Google Scholar 

  67. Weihs, G., Jennewein, T., Simon, C., Weinfurter, H. & Zeilinger, A. Violation of Bell's inequalities under strict Einstein locality conditions. Phys. Rev. Lett. 81, 5039–5034 (1998).

    ADS  MathSciNet  MATH  Google Scholar 

  68. Scheidl, T. et al. Violation of local realism with freedom of choice. Proc. Natl Acad. Sci. USA 107, 19708–19713 (2010).

    ADS  MATH  Google Scholar 

  69. Wiseman, H. M., Jones, S. J. & Doherty, A. C. Steering, entanglement, nonlocality, and the Einstein–Podolsky–Rosen paradox. Phys. Rev. Lett. 98, 140402 (2007).

    ADS  MathSciNet  MATH  Google Scholar 

  70. Jones, S. J., Wiseman, H. M. & Doherty, A. C. Entanglement, Einstein–Podolsky–Rosen correlations, Bell nonlocality, and steering. Phys. Rev. A 76, 052116 (2007).

    ADS  MathSciNet  MATH  Google Scholar 

  71. Cavalcanti, E. G., Jones, S. J., Wiseman, H. M. & Reid, M. D. Experimental criteria for steering and the Einstein–Podolsky–Rosen paradox. Phys. Rev. A 80, 032112 (2009).

    ADS  Google Scholar 

  72. Plenio, M. B. & Virmani, S. An introduction to entanglement measures. Quant. Inf. Comput. 7, 1–51 (2007).

    MathSciNet  MATH  Google Scholar 

  73. Saunders, D. J., Jones, S. J., Wiseman, H. M. & Pryde, G. J. Experimental EPR-steering using Bell-local states. Nature Phys. 6, 845–849 (2010).

    ADS  Google Scholar 

  74. Bennet, A. J. et al. Arbitrarily loss-tolerant Einstein–Podolsky–Rosen steering allowing a demonstration over 1 km of optical fibre with no detection loophole. Phys. Rev. X 2, 031003 (2012).

    Google Scholar 

  75. Smith, D. H. et al. Conclusive quantum steering with superconducting transition-edge sensors. Nature Commun. 3, 625 (2012).

    ADS  Google Scholar 

  76. Wittmann, B. et al. Loophole-free Einstein–Podolsky–Rosen experiment via quantum steering. New J. Phys. 14, 053030 (2012).

    ADS  Google Scholar 

  77. Cabello, A. Bell's theorem without inequalities and without alignments. Phys. Rev. Lett. 91, 230403 (2003).

    ADS  MathSciNet  Google Scholar 

  78. D'Ambrosio, V. et al. Complete experimental toolbox for alignment-free quantum communication. Nature Commun. 3, 961 (2012).

    ADS  Google Scholar 

  79. Palsson, M. S., Wallman, J. J., Bennet, A. J. & Pryde, G. J. Experimentally demonstrating reference-frame-independent violations of Bell inequalities. Phys. Rev. A 86, 032322 (2012).

    ADS  Google Scholar 

  80. Shadbolt, P. J. et al. Guaranteed violation of a Bell inequality without aligned reference frames or calibrated devices. Sci. Rep. 2, 470 (2012).

    Google Scholar 

  81. Wallman, J. J. & Bartlett, S. D. Observers can always generate nonlocal correlations without aligning measurements by covering all their bases. Phys. Rev. A 85, 024101 (2012).

    ADS  Google Scholar 

  82. Greenberger, D. M., Horne, M. A. & Zeilinger, A. Bell's Theorem, Quantum Theory, and Conceptions of the Universe (ed. Kafatos, M.) 69–72 (Kluwer, 1989)

    Google Scholar 

  83. Mermin, N. D. Extreme quantum entanglement in a superposition of macroscopically distinct states. Phys. Rev. Lett. 65, 1838–1840 (1990).

    ADS  MathSciNet  MATH  Google Scholar 

  84. Bouwmeester, D., Pan, J. W., Daniell, M., Weinfurter, H. & Zeilinger, A. Observation of three-photon Greenberger–Horne–Zeilinger entanglement. Phys. Rev. Lett. 82, 1345–1349 (1999).

    ADS  MathSciNet  MATH  Google Scholar 

  85. Pan, J-W., Bouwmeester, D., Daniell, M., Weinfurter, H. & Zeilinger, A. Experimental tests of quantum nonlocality in three-photon Greenberger–Horne–Zeilinger experiment. Nature 403, 515–519 (2000).

    ADS  Google Scholar 

  86. Pan, J-W., Daniell, M., Gasparoni, S., Weihs, G. & Zeilinger, A. Experimental demonstration of four-photon entanglement and high-fidelity teleportation. Phys. Rev. Lett. 86, 4435–4438 (2001).

    ADS  Google Scholar 

  87. Eibl, M. et al. Experimental observation of four-photon entanglement from parametric down-conversion. Phys.Rev. Lett. 90, 200403 (2003).

    ADS  Google Scholar 

  88. Zhao, Z. et al. Experimental violation of local realism by four-photon Greenberger–Horne–Zeilinger entanglement. Phys. Rev. Lett. 912, 180401 (2003).

    Google Scholar 

  89. Erven, C. et al. Experimental three-particle quantum nonlocality under strict locality conditions. Nature Photon. 8, http://dx.doi.org/nphoton.2014.50 (2014).

    ADS  Google Scholar 

  90. Nielsen, M. A. & Chuang, I. L. Quantum Computation and Quantum Information (Cambridge Univ. Press, 2010).

    MATH  Google Scholar 

  91. Shor, P. W. in Proc. 35th Ann. Symp. Found. Comput. Sci. 124–134 (IEEE, 1994).

    Google Scholar 

  92. Aaronson, S. & Arkhipov, A. in STOC '11: Proc. 43rd Ann. ACM Symp.Theory Comput. 333–342 (ACM, 2011).

    Google Scholar 

  93. Politi, A., Cryan, M. J., Rarity, J. G., Yu, S. & O'Brien, J. L. Silica-on-silicon waveguide quantum circuits. Science 320, 646–649 (2008).

    ADS  Google Scholar 

  94. Broome, M. A. et al. Photonic boson sampling in a tunable circuit. Science 339, 794–798 (2013).

    ADS  Google Scholar 

  95. Spring, J. B. et al. Boson sampling on a photonic chip. Science 339, 798–801 (2013).

    ADS  Google Scholar 

  96. Crespi, A. et al. Experimental boson sampling in arbitrary integrated photonic circuits. Nature Photon. 7, 545–549 (2013).

    ADS  Google Scholar 

  97. Tillmann, M. et al. Experimental boson sampling. Nature Photon. 7, 540–544 (2013).

    ADS  Google Scholar 

  98. Kwiat, P. G. et al. New high-intensity source of polarization-entangled photon pairs. Phys. Rev. Lett. 75, 4337–4341 (1995).

    ADS  Google Scholar 

  99. Predojevic, A., Grabher, S. & Weihs, G. Pulsed Sagnac source of polarisation entangled photon pairs. Opt. Express 20, 25022–25029 (2012).

    ADS  Google Scholar 

  100. Guerreiro, T. et al. High efficiency coupling of photon pairs in practice. Opt. Express 21, 27641–27651 (2013).

    ADS  Google Scholar 

  101. Silverstone, J. et al. On-chip quantum interference between two silicon waveguide sources. Nature Photon. 8, 104–108 (2013).

    ADS  Google Scholar 

  102. Matsuda, N. et al. A monolithically integrated polarization entangled photon pair source on a silicon chip. Sci. Rep. 2, 817 (2012).

    Google Scholar 

  103. Hadfield, R. H. Single-photon detectors for optical quantum information applications. Nature Photon. 3, 696–705 (2009).

    ADS  Google Scholar 

  104. Gol'tsman, G. N. et al. Picosecond superconducting single-photon optical detector. Appl. Phys. Lett. 79, 705 (2001).

    ADS  Google Scholar 

  105. Pernice, W. H. P. et al. High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits. Nature Commun. 3, 1325 (2012).

    ADS  Google Scholar 

  106. Schuck, C., Pernice, W. H. P. & Tang, H. X. Waveguide integrated low noise NbTiN nanowire single-photon detectors with milli-Hz dark count rate. Sci. Rep. 3, 1893 (2013).

    ADS  Google Scholar 

Download references

Acknowledgements

We are grateful for financial support from EPSRC, ERC, NSQI (S.G.). J.C.F.M. is supported by a Leverhulme Trust Early-Career Fellowship. J.L.O.B. acknowledges a Royal Society Wolfson Merit Award and a Royal Academy of Engineering Chair in Emerging Technologies. We thank P. Birchall, N. Brunner and C. Sparrow for helpful comments.

Author information

Authors and Affiliations

  1. H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, Centre for Quantum Photonics, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol, BS8 1UB, UK

    Peter Shadbolt, Jonathan C. F. Mathews, Anthony Laing & Jeremy L. O'Brien

Authors
  1. Peter Shadbolt
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jonathan C. F. Mathews
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Anthony Laing
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Jeremy L. O'Brien
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Jonathan C. F. Mathews.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Shadbolt, P., Mathews, J., Laing, A. et al. Testing foundations of quantum mechanics with photons. Nature Phys 10, 278–286 (2014). https://doi.org/10.1038/nphys2931

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nphys2931

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing