image:
Physicists at UC Berkeley immobilized small clusters of cesium atoms (pink blobs) in a vertical vacuum chamber, then split each atom into a quantum state in which half of the atom was closer to a tungsten weight (shiny cylinder) than the other half (split spheres below the tungsten). By measuring the phase difference between the two halves of the atomic wave function, they were able to calculate the difference in the gravitational attraction between the two parts of the atom, which matched what is expected from Newtonian gravity.
Credit: Cristian Panda/UC Berkeley
Dark energy a mysterious force pushing the universe apart at an ever-increasing rate was discovered 26 years ago, and ever since, scientists have been searching for a new and exotic particle causing the expansion.
Pushing the boundaries of this search, University of California, Berkeley physicists have now built the most precise experiment yet to look for minor deviations from the accepted theory of gravity that could be evidence for such a particle, which theorists have dubbed a chameleon or symmetron.
The experiment, which combines an atom interferometer for precise gravity measurements with an optical lattice to hold the atoms in place, allowed the researchers to immobilize free-falling atoms for seconds instead of milliseconds to look for gravitational effects, besting the current most precise measurement by a factor of five.
Though the researchers found no deviation from what is predicted by the theory spelled out by Isaac Newton 400 years ago, expected improvements in the precision of the experiment could eventually turn up evidence that supports or disproves theories of a hypothetical fifth force mediated by chameleons or symmetrons.
The ability of the lattice atom interferometer to hold atoms for up to 70 seconds and potentially 10 times longer also opens up the possibility of probing gravity at the quantum level, said Holger Mller, UC Berkeley professor of physics. While physicists have well-tested theories describing the quantum nature of three of the four forces of nature electromagnetism and the strong and weak forces the quantum nature of gravity has never been demonstrated.
"Most theorists probably agree that gravity is quantum. But nobody has ever seen an experimental signature of that," Mller said. "It's very hard to even know whether gravity is quantum, but if we could hold our atoms 20 or 30 times longer than anyone else, because our sensitivity increases with the second or fourth power of the hold time, we could have a 400 to 800,000 times better chance of finding experimental proof that gravity is indeed quantum mechanical."
Aside from precision measurements of gravity, other applications of the lattice atom interferometer include quantum sensing.
"Atom interferometry is particularly sensitive to gravity or inertial effects. You can build gyroscopes and accelerometers," said UC Berkeley postdoctoral fellow Cristian Panda, who is first author of a paper about the gravity measurements set to be published this week in the journal Nature and is co-authored by Mller. "But this gives a new direction in atom interferometry, where quantum sensing of gravity, acceleration and rotation could be done with atoms held in optical lattices in a compact package that is resilient to environmental imperfections or noise."
Because the optical lattice holds atoms rigidly in place, the lattice atom interferometer could even operate at sea, where sensitive gravity measurements are employed to map the geology of the ocean floor.
Dark energy was discovered in 1998 by two teams of scientists: a group of physicists based at Lawrence Berkeley National Laboratory, led by Saul Perlmutter, now a UC Berkeley professor of physics, and a group of astronomers that included UC Berkeley postdoctoral fellow Adam Riess. The two shared the 2011 Nobel Prize in Physics for the discovery.
The realization that the universe was expanding more rapidly than it should came from tracking distant supernovas and using them to measure cosmic distances. Despite much speculation by theorists about what's actually pushing space apart, dark energy remains an enigma a large enigma, since about 70% of the entire matter and energy of the universe is in the form of dark energy.
One theory is that dark energy is merely the vacuum energy of space. Another is that it is an energy field called quintessence, which varies over time and space.
Another proposal is that dark energy is a fifth force much weaker than gravity and mediated by a particle that exerts a repulsive force that varies with the density of surrounding matter. In the emptiness of space, it would exert a repulsive force over long distances, able to push space apart. In a laboratory on Earth, with matter all around to shield it, the particle would have an extremely small reach.
This particle has been dubbed a chameleon, as if it's hiding in plain sight.
In 2015, Mller adapted an atom interferometer to search for evidence of chameleons using cesium atoms launched into a vacuum chamber, which mimics the emptiness of space. During the 10 to 20 milliseconds it took the atoms to rise and fall above a heavy aluminum sphere, he and his team detected no deviation from what would be expected from the normal gravitational attraction of the sphere and Earth.
The key to using free-falling atoms to test gravity is the ability to excite each atom into a quantum superposition of two states, each with a slightly different momentum that carries them different distances from a heavy tungsten weight hanging overhead. The higher momentum, higher elevation state experiences more gravitational attraction to the tungsten, changing its phase. When the atom's wave function collapses, the phase difference between the two parts of the matter wave reveals the difference in gravitational attraction between them.
"Atom interferometry is the art and science of using the quantum properties of a particle, that is, the fact that it's both a particle and a wave. We split the wave up so that the particle is taking two paths at the same time and then interfere them at the end," Mller said. "The waves can either be in phase and add up, or the waves can be out of phase and cancel each other out. The trick is that whether they are in phase or out of phase depends very sensitively on some quantities that you might want to measure, such as acceleration, gravity, rotation or fundamental constants."
In 2019, Mller and his colleagues added an optical lattice to keep the atoms close to the tungsten weight for a much longer time an astounding 20 seconds to increase the effect of gravity on the phase. The optical lattice employs two crossed laser beams that create a lattice-like array of stable places for atoms to congregate, levitating in the vacuum. But was 20 seconds the limit, he wondered?
During the height of the COVID-19 pandemic, Panda worked tirelessly to extend the hold time, systematically fixing a list of 40 possible roadblocks until establishing that the wiggling tilt of the laser beam, caused by vibrations, was a major limitation. By stabilizing the beam within a resonant chamber and tweaking the temperature to be a bit colder in this case less than a millionth of a Kelvin above absolute zero, or a billion times colder than room temperature he was able to extend the hold time to 70 seconds.
He and Mller published those results in the June 11, 2024, issue of Nature Physics.
In the newly reported gravity experiment, Panda and Mller traded a shorter time, 2 seconds, for a greater separation of the wave packets to several microns, or several thousandths of a millimeter. There are about 10,000 cesium atoms in the vacuum chamber for each experiment too sparsely distributed to interact with one another dispersed by the optical lattice into clouds of about 10 atoms each.
"Gravity is trying to push them down with a force a billion times stronger than their attraction to the tungsten mass, but you have the restoring force from the optical lattice that's holding them, kind of like a shelf," Panda said. "We then take each atom and split it into two wave packets, so now it's in a superposition of two heights. And then we take each one of those two wave packets and load them in a separate lattice site, a separate shelf, so it looks like a cupboard. When we turn off the lattice, the wave packets recombine, and all the quantum information that was acquired during the hold can be read out."
Panda plans to build his own lattice atom interferometer at the University of Arizona, where he was just appointed an assistant professor of physics. He hopes to use it to, among other things, more precisely measure the gravitational constant that links the force of gravity with mass.
Meanwhile, Mller and his team are building from scratch a new lattice atom interferometer with better vibration control and a lower temperature. The new device could produce results that are 100 times better than the current experiment, sensitive enough to detect the quantum properties of gravity. The planned experiment to detect gravitational entanglement, if successful, would be akin to the first demonstration of quantum entanglement of photons performed at UC Berkeley in 1972 by the late Stuart Freedman and former postdoctoral fellow John Clauser. Clauser shared the 2022 Nobel Prize in Physics for that work.
Other co-authors of the gravity paper are graduate student Matthew Tao and former undergraduate student Miguel Ceja of UC Berkeley, Justin Khoury of the University of Pennsylvania in Philadelphia and Guglielmo Tino of the University of Florence in Italy. The work is supported by the National Science Foundation (1708160, 2208029), Office of Naval Research (N00014-20-1-2656) and Jet Propulsion Laboratory (1659506, 1669913).
Experimental study
Measuring gravitational attraction with a lattice atom interferometer
26-Jun-2024
More here:
Precision instrument bolsters efforts to find elusive dark energy - EurekAlert
- Wolfram Physics Project Seeks Theory Of Everything; Is It Revelation Or Overstatement? - Hackaday [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Elon Musk and Grimes Named Their Baby X A-12, Which Must Mean SomethingRight? - Esquire [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Free Will Astrology - Week of May 7 | Advice & Fun | Bend - The Source Weekly [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Free Will Astrology: May 6, 2020 - River Cities Reader [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Is string theory worth it? - Space.com [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Finding the right quantum materials - MIT News [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Quantum Tunneling Effects, Solving the Schrodinger Equation Bottleneck Recognized as Best Papers by The Journal of Chemical Physics - PRNewswire [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- What Is Quantum Mechanics? Quantum Physics Defined ... [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Quantum Physics Overview, Concepts, and History [Last Updated On: May 6th, 2020] [Originally Added On: May 6th, 2020]
- Tisca Chopra: This time has given me time to think about time - Daijiworld.com [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- Iron-Based Material has the Ability to Power Small Devices - AZoNano [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- How Einstein Failed to Find Flaws in the Copenhagen Interpretation - The Great Courses Daily News [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- Raytheon Technologies Reports First Quarter 2020 Results; Greg Hayes Quoted - ExecutiveBiz [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- Unified Field Theory: Einstein Failed, but What's the Future? - The Great Courses Daily News [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- Einstein Vs. the New Generation of Quantum Theorists - The Great Courses Daily News [Last Updated On: May 7th, 2020] [Originally Added On: May 7th, 2020]
- Why Self-Awareness and Communication Are Key for Self-Taught Players and Luthiers - Premier Guitar [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- Nine graduates head off to continue their higher educational pursuits - Nevada Today [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- 'The Theory of Everything' by Wolfram Gets Criticized by Physicists - Interesting Engineering [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- Cliff's Edge -- The Past Hypothesis - Adventist Review [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- Researchers Have Found a New Way to Convert Waste Heat Into Electricity to Power Small Devices - SciTechDaily [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- Quantum Computing Market New Technology Innovations, Advancements and Global Development Analysis 2020 to 2025 - Cole of Duty [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- Physicist Brian Greene on learning to focus on the here and now - KCRW [Last Updated On: May 10th, 2020] [Originally Added On: May 10th, 2020]
- OK, WTF Are Virtual Particles and Do They Actually Exist? - VICE [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Is the Big Bang in crisis? | Astronomy.com - Astronomy Magazine [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Raytheon Technologies Board of Directors to Take Voluntary Compensation Reduction - PRNewswire [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- What part of 'public' does PSC not get? - The Bozeman Daily Chronicle [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Exploring new tools in string theory - Space.com [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- The Era of Anomalies - Physics [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Registration Open for Inaugural IEEE International Conference on Quantum Computing and Engineering (QCE20) - thepress.net [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Exploring the quantum field, from the sun's core to the Big Bang - MIT News [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- The strange link between the human mind and quantum physics [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- quantum mechanics | Definition, Development, & Equations ... [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Quantum Physics Introduction Made Simple for Beginners [Last Updated On: May 15th, 2020] [Originally Added On: May 15th, 2020]
- Company Hopes to Have Carbon Nanotube COVID-19 Detector Available in June - SciTechDaily [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- The world is not as real as we think. - Patheos [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- Armin Strom Discusses Resonance With PhD Of Quantum Physics And Watch Collector In An Easy-To-Understand Way (Video) - Quill & Pad [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- Teaching the next generation of quantum scientists | Harvard John A. Paulson School of Engineering and Applied Sciences - Harvard School of... [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- Nasa discovers parallel universe where time runs backwards? Know the truth - Business Standard [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- Physicists Just Built The First Working Prototype Of A 'Quantum Radar' - ScienceAlert [Last Updated On: May 23rd, 2020] [Originally Added On: May 23rd, 2020]
- Next-Gen Laser Beams With Up to 10 Petawatts of Power Will Usher In New Era of Relativistic Plasmas Research - SciTechDaily [Last Updated On: May 26th, 2020] [Originally Added On: May 26th, 2020]
- What does the Tenet title mean? Quantum mechanics and Einsteins theory - Explica [Last Updated On: May 26th, 2020] [Originally Added On: May 26th, 2020]
- Looking up: UFO occupants and the legacy of language - Roswell Daily Record [Last Updated On: May 26th, 2020] [Originally Added On: May 26th, 2020]
- This is the light they have discovered and according to scientists it should not exist - Checkersaga [Last Updated On: June 2nd, 2020] [Originally Added On: June 2nd, 2020]
- MIT Student Probing Reality Through Physics, Philosophy and Writing - SciTechDaily [Last Updated On: June 2nd, 2020] [Originally Added On: June 2nd, 2020]
- David Baddiel: Kids have a better sense of humour than they used to' - The Guardian [Last Updated On: June 2nd, 2020] [Originally Added On: June 2nd, 2020]
- Some Information Regarding Medical Physics - - KUSI [Last Updated On: June 2nd, 2020] [Originally Added On: June 2nd, 2020]
- Francesca Vidotto: The Quantum Properties of Space-Time - JSTOR Daily [Last Updated On: June 2nd, 2020] [Originally Added On: June 2nd, 2020]
- These 8 Books Have the Power to Change Your Perspective on Life - Morocco World News [Last Updated On: June 8th, 2020] [Originally Added On: June 8th, 2020]
- Could Every Electron in the Universe Be the Same One? - Interesting Engineering [Last Updated On: June 8th, 2020] [Originally Added On: June 8th, 2020]
- Armijo: The absolute power of love | VailDaily.com - Vail Daily News [Last Updated On: June 8th, 2020] [Originally Added On: June 8th, 2020]
- Scientists predicted that the coronavirus death rate would fall over time, but instead it doubled. Here's why - Business Insider India [Last Updated On: June 13th, 2020] [Originally Added On: June 13th, 2020]
- Sussex Uni physicist creates the fifth state of matter whilst working from home - The Tab [Last Updated On: June 13th, 2020] [Originally Added On: June 13th, 2020]
- Beware of 'Theories of Everything' - Scientific American [Last Updated On: June 13th, 2020] [Originally Added On: June 13th, 2020]
- Duckworth on Education: The Feynman Technique - EMSWorld [Last Updated On: June 13th, 2020] [Originally Added On: June 13th, 2020]
- Scientists Discover Quantum Matter for the First Time in Space - Beebom [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- Physicists May Have Solved Long-Standing Mystery of Matter and Antimatter - SciTechDaily [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- Louis Broglie and the Idea of Wave-Particle Duality - Interesting Engineering [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- Letter reveals the quirky side of Albert Einstein - Chile News | Breaking News, Views, Analysis - The Santiago Times [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- Exploring the Quantum Field, From the Suns Core to the Big Bang at MIT - SciTechDaily [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- 10 of the best non-fiction science books to read right now - New Scientist [Last Updated On: June 14th, 2020] [Originally Added On: June 14th, 2020]
- Quantum material research connecting physicists in Hong Kong, Beijing and Shanghai facilitates discovery of better materials that benefit our society... [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- Flattening The Complexity Of Quantum Circuits - Asian Scientist Magazine [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- Borrowing from robotics, scientists automate mapping of quantum systems - News - The University of Sydney [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- Weird green glow spotted in atmosphere of Mars - Space.com [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- Why Gravity Is Not Like the Other Forces - Quanta Magazine [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- Cedar Hill grad pivots from science to law, determined to help others - The Dallas Morning News [Last Updated On: June 16th, 2020] [Originally Added On: June 16th, 2020]
- The stories a muon could tell - Symmetry magazine [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- In the atmosphere of Mars, a green glow offers scientists hints for future visits - NBCNews.com [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- Birdsong offers clues to the workings of short-term memory - AroundtheO [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- Restructuring cybersecurity with the power of quantum - TechRadar [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- Researchers Use Richard Feynman's Ideas to Develop a Working 'Theory of Everything' - Interesting Engineering [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- Nano-motor of just 16 atoms runs at the boundary of quantum physics - New Atlas [Last Updated On: June 18th, 2020] [Originally Added On: June 18th, 2020]
- 'Everything was centered around Sara, he was lost': Abhishek Kapoor on Sushant Singh Rajput after 'Kedarnath' - DNA India [Last Updated On: June 21st, 2020] [Originally Added On: June 21st, 2020]
- Physicists have proposed a new theory for Bose-Einstein condensates - Tech Explorist [Last Updated On: June 21st, 2020] [Originally Added On: June 21st, 2020]
- 8.13 and 8.14: Physics Junior Lab - MIT Technology Review [Last Updated On: June 21st, 2020] [Originally Added On: June 21st, 2020]
- The Period of the Universe's Clock - Physics [Last Updated On: June 21st, 2020] [Originally Added On: June 21st, 2020]
- If Wormholes Are Actually Going to Work, They'll Need to Look Weird - Yahoo! Voices [Last Updated On: June 25th, 2020] [Originally Added On: June 25th, 2020]
- At Long Last: An Answer to the Mystery Surrounding Matter and Antimatter - SciTechDaily [Last Updated On: June 25th, 2020] [Originally Added On: June 25th, 2020]
- Lost and found in French translation - The Guardian [Last Updated On: June 25th, 2020] [Originally Added On: June 25th, 2020]
- Do we need a 'Quantum Generation'? | TheHill - The Hill [Last Updated On: June 25th, 2020] [Originally Added On: June 25th, 2020]