{"id":33904,"date":"2025-07-31T02:25:07","date_gmt":"2025-07-31T02:25:07","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/33904\/"},"modified":"2025-07-31T02:25:07","modified_gmt":"2025-07-31T02:25:07","slug":"mit-finds-einstein-was-wrong-in-100-year-old-wave-particle-dispute-with-niels-bohr","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/33904\/","title":{"rendered":"MIT finds Einstein was wrong in 100-year-old wave-particle dispute with Niels Bohr"},"content":{"rendered":"

In a striking display of quantum physics<\/a>, a team of researchers has recreated one of science\u2019s most legendary experiments\u2014with unprecedented precision. At MIT<\/a>, scientists cooled thousands of atoms to nearly absolute zero, arranged them in a neat lattice using laser light, and then used those atoms to scatter individual photons of light. <\/p>\n

The experiment is a modern version of the double-slit experiment, designed to test whether light behaves like a wave or a particle. It\u2019s an old question\u2014but now answered in an impressively pure and direct way.<\/p>\n

The results not only deepen understanding of quantum mechanics, they also prove that Albert Einstein<\/a>\u2019s explanation of the experiment fell short. His idea\u2014that it might be possible to measure both the path of light and its interference pattern\u2014turns out not to hold up when tested at the atomic level. <\/p>\n

This modern approach to a classic quantum thought experiment shows what\u2019s possible when technology meets the most abstract scientific ideas. It also clarifies one of the most famous disputes in physics, first argued between Einstein and Niels Bohr almost 100 years ago.<\/p>\n

Schematic of the MIT experiment: Two single atoms floating in a vacuum chamber are illuminated by a laser beam and act as the two slits. (CREDIT: Wolfgang Ketterle, et al.) A Fresh Look at a Classic Experiment<\/p>\n

The double-slit experiment is often introduced in high school classrooms to illustrate quantum weirdness. First performed by Thomas Young in 1801, it originally showed that light acts like a wave. Later, with the rise of quantum theory, it also became evidence that light behaves like a particle, or photon<\/a>.<\/p>\n

In the original setup, light shines through two slits and hits a screen. If photons acted only like particles, they would create two bright spots. Instead, they form a wave-like interference pattern, unless you measure which slit the photon passed through. Once you try measuring the path, the interference pattern disappears and the light acts like a stream of particles.<\/p>\n

This strange result caused many years of scientific debate. Einstein argued that if a photon caused a small “kick” as it passed through a slit, its path could be traced. He believed this might let you observe both the photon\u2019s path and the interference pattern. Bohr<\/a> disagreed, using the uncertainty principle to argue any measurement would destroy the interference pattern. His explanation became a key part of quantum theory. Still, Einstein was not convinced.<\/p>\n

Related StoriesGoing Smaller, Colder, and Clearer<\/p>\n

To test this idea more purely, Wolfgang Ketterle and his MIT team used ultracold atoms. They trapped over 10,000 atoms in a tight grid using lasers<\/a> and cooled them to microkelvin temperatures. That\u2019s just above absolute zero, where atoms behave in fully quantum ways. These atoms acted as the tiniest slits ever used. <\/p>\n

Earlier experiments used fixed slits or physical barriers. But here, each atom stood alone, identical, and ready to interact with just one photon. The researchers shone a weak beam of light on the array. Most atoms scattered only one photon each.<\/p>\n

They adjusted the atoms\u2019 \u201cfuzziness,\u201d which means how well the atom\u2019s position was known. Fuzzier atoms gave away more information about a photon\u2019s path. That made the interference pattern<\/a> weaker. When the atom’s position was clearer, less path information was revealed. That made the interference pattern stronger. They tuned the fuzziness by tightening or loosening the laser traps. This let them control whether the light behaved more like particles or waves.<\/p>\n

The team standing with their creation. (CREDIT: Ketterle Lab) Light, Fuzziness, and Quantum Correlations<\/p>\n

Their findings were published in Physical Review Letters<\/a>. They showed the interference pattern weakens when more path information is available. This result agrees with quantum theory and supports Bohr\u2019s interpretation. Einstein had imagined that a photon would disturb one slit, like a bird brushing a branch. <\/p>\n

But the experiment did not support that idea. Ketterle\u2019s team found physical disturbance or \u201cspring\u201d setups were not important. The key was quantum fuzziness\u2014uncertainty in the atom\u2019s position.<\/p>\n

Ketterle said, \u201cEinstein and Bohr would have never thought that this is possible, to perform such an experiment with single atoms and single photons.\u201d \u201cWhat we have done is an idealized Gedanken experiment.\u201d Vitaly Fedoseev, the lead author, said, \u201cWe realized we can quantify the degree to which this scattering process is like a particle or a wave<\/a>.\u201d The team could measure how one photon scattered between two atoms, like light going through slits.<\/p>\n

Light scattering from two atomic wavepackets. The light has a coherent part which results in interference fringes, and an incoherent part resulting in a finite contrast of the fringes. The incoherent fraction originates from partial entanglement between the atoms and photons. (CREDIT: Physical Review Letters) Cutting the Strings\u2014And Still Getting the Same Result<\/p>\n

To test the role of disturbance\u2014Einstein\u2019s \u201cspring\u201d\u2014the team made a change. At first, atoms were held in place by lasers, like slits fixed by springs. In later trials, they turned off the lasers<\/a> and let atoms float freely. They measured scattering in just microseconds, before gravity pulled the atoms down or made them fuzzier. <\/p>\n

The results matched the previous ones when the atoms were held. That showed the spring-like setup didn\u2019t affect the photon\u2019s behavior.<\/p>\n

Fedoseev explained, \u201cIn many descriptions, the springs play a major role. But we show, no, the springs do not matter here; what matters is only the fuzziness of the atoms<\/a>.\u201d \u201cOne has to use a more profound description, which uses quantum correlations between photons and atoms.\u201d So it wasn\u2019t any physical movement that caused the change. It was how much quantum information was shared between photon and atom.<\/p>\n

Light scattering from expanding wavepackets. Lithium (a) atoms are prepared in a Mott insulating state in a deep (blue) or shallow (red) optical lattice. (CREDIT: Physical Review Letters) A Quantum Year, A Quantum Result<\/p>\n

The experiment came at a perfect time. The United Nations named 2025 the International Year of Quantum Science and Technology. This marks 100 years since quantum mechanics<\/a> was introduced. Bohr and Einstein\u2019s debate happened just two years after that, in 1927. Now, almost a century later, MIT scientists offer one of the clearest answers yet.<\/p>\n

Their version of the experiment used single atoms as the tiniest slits possible. It confirmed that wave-particle duality depends on quantum uncertainty. You cannot know a photon\u2019s path and still see its wave pattern. While this may not change quantum theory itself, it proves how far technology has come. It lets scientists revisit old questions with sharper, cleaner experiments.<\/p>\n","protected":false},"excerpt":{"rendered":"In a striking display of quantum physics, a team of researchers has recreated one of science\u2019s most legendary…\n","protected":false},"author":2,"featured_media":33905,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[64,63,292,128],"class_list":["post-33904","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-au","tag-australia","tag-physics","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/33904","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=33904"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/33904\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/33905"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=33904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=33904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=33904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}