Is Gravity Quantum? New Experiment To Probe Universe’s Deepest Mystery

Quantum Gravity Concept Art Illustration

Scientists from several universities are collaborating on an experiment named ‘MAST-QG’ to determine if gravity has quantum properties. The experiment, which involves levitating microdiamonds in quantum superposition, aims to unite general relativity and quantum mechanics. Despite its complexity, this research could fundamentally alter our understanding of gravity and has broad implications for physics. Credit:

  • Scientists are developing an experiment to test whether gravity is quantum
  • In quantum mechanics, which describes the behavior of atoms and molecules –objects behave differently to everything we know: they can be in a quantum superposition of being in two places at the same time
  • Now, scientists are investigating a way to determine whether gravity operates in this way, by levitating micro diamonds in a vacuum
  • If gravity is quantum, it will ‘entangle’ the diamonds – an intriguing phenomenon that strongly links two objects in ways impossible in everyday life
  • This research will help drive understanding of black holes, the Big Bang, and the universe

Quantum Gravity Experiment

Scientists are developing an experiment to test whether gravity is quantum – one of the deepest questions about our universe.

General relativity and quantum mechanics are the two most fundamental descriptions of nature we have. General relativity explains gravity on large scales while quantum mechanics explains the behaviour of atoms and molecules.

The Challenge of Unifying Theories

Arguably the most important unsolved problem in fundamental physics is the correct way to bring these two theories together – to determine whether gravity operates on a quantum level. While theoretical work has proposed many possibilities, experiments are needed to fully understand the behavior of gravity.

Laser Beam Probes Quantum Properties of Diamond

A laser beam in Gavin Morley’s lab probes the quantum properties of a diamond. Credit: Gavin Morley

Revolutionary Experiment by Global Consortium

For a hundred years experiments on the quantum nature of gravity seemed out of reach, but now scientists based at the Universities of Warwick, UCL, Yale (USA), Northwestern (USA), and Groningen (Holland) will work together to investigate this conundrum.

Their new idea is to levitate two microdiamonds in vacuum and put each into a quantum superposition of being in two places at the same time. This counterintuitive behavior is a fundamental feature of quantum mechanics.

Professor Morley’s Insight on the Experiment

Each diamond can be thought of as a smaller version of Schrödinger’s cat. Principal Investigator Professor Gavin Morley, Department of Physics, University of Warwick, explains: “Schrödinger’s cat is a thought experiment pointing out that it would be really weird if everyday objects (and pets!) could be in a quantum superposition of being in two places at once. We want to test the limits of this idea.

“Atoms and molecules have been successfully put into such a superposition state, but we want to do this with much larger objects. Our diamonds are made up of one billion atoms or more. To test the quantum nature of gravity, we would look for interactions between two such diamonds due to gravity.

“If gravity is quantum, then it would be able to entangle the two diamonds. Entanglement is a unique quantum effect where two things are linked more strongly than is possible in our everyday life. For example, if two coins could be entangled then you might find that whenever you flip them, they both land the same way up even if it’s impossible to know in advance if they will both be heads or both tails.”

Challenges and Implications

There are still many challenges to realizing this idea, which the team will investigate during the project. “For example, we need to eliminate all interactions between the nanoparticles other than gravity, which is incredibly challenging since gravity is so weak,” says Dr. David Moore, of Yale University.

Professor Morley, who is the founding director of Warwick Quantum, a new interdisciplinary initiative for Quantum Technology research, added: “For me, the most important problem in physics right now is to develop an experiment that can test the quantum nature of gravity. This new project is an acceleration in our exciting journey towards this.

Perspectives From Collaborating Scientists

Professor Sougato Bose, UCL, commented “It is hard to overstate how significant it would be for physicists to have experiments that could probe the correct way to combine quantum mechanics and general relativity. People working on theories of quantum gravity such as string theory typically focus on what’s happening at high energies, near black holes, and at the Big Bang.

“In contrast, our work is in the low-energy regime right here on Earth, but it would also provide invaluable information about whether gravity is quantum. Also, the experiment can be regarded as the verification of a generic prediction of any quantum theory of gravity at low energies.”

Professor Anupam Mazumdar, University of Groningen, adds “On the way to understanding the quantum nature of gravity, we may be able to test other aspects of fundamental physics such as exotic deviations from Newtonian gravity as short distances.”

“This is a challenging experiment, and this project is a pathfinder to address some of the key technical challenges to make these tests of quantum aspects of gravity a reality”, says Andrew Geraci, Associate Professor of Physics, Northwestern University.

The project is called ‘MAST-QG: Macroscopic superpositions towards witnessing the quantum nature of gravity’.

11 Comments on "Is Gravity Quantum? New Experiment To Probe Universe’s Deepest Mystery"

  1. Fixed gravity for you. | December 14, 2023 at 9:09 pm | Reply

    It’s great they’re talking about searching for signs quantized gravity at low energy, but it seems more constructive to do that by thinking about how quantizing gravity may explain things already evident, such as the inability to pin down “big G” with great precision, frame dragging and dark sector effects, as opposed to looking for unobservable things like imaginary “superposition of being in two places at once.” One has to be open to seeing general relativity’s supposed adequacy as a sort of artificial intelligence hallucination that enables tribal denials in the missing of obvious things.

    True superposition may be allowed with particles of light (true fundamental bosons – photons) because these particles are massless. Electrons, atoms and molecules can naturally be induced to magnetically pair up in complementary states, generating experimental signal drop-out and avoiding apparatus ambient noise as composite bosons without actually sharing the space of a single electron, atom or molecule, but coming extremely close to that. Even flattened buckyballs should pair up into magnetic dipoles. How about entangling two sheets of graphene first, before two lumps of diamond, so you don’t appear too eager to fail.

    • Fixed gravity for you. | December 14, 2023 at 10:47 pm | Reply

      “How about entangling two sheets of graphene first”

      … where they aren’t touching, of course. Seems that spinning both in sync on a common axis in extreme cold should help with isolation. Seems hydrogenating both sheets should be a huge help.

      Also, “signs quantized gravity” should be “signs of quantized gravity” and a larger text input window would be nice.

  2. I think of gravity being a manifestation of weight being that we live in a closed system on earth the evidence of gravity at the quantum level and being a weak force would be near impossible to detect. As far as entanglement I consider it at being in the same spin orientation in the multitude amount of quantum particles to separate the quantum would only give the attributes of a singled out quantum particle. A question to be asked is entanglement at a certain distance or does it very in the amount of similar quantum particles in an area.

  3. Fixed gravity for you. | December 16, 2023 at 4:07 am | Reply

    Some quotes from other publications, a few years ago —-

    “And waves occupy multiple places in space at once. So any chunk of matter can also occupy two places at once.” – Rafi Letzter (Scientific American)

    Rafi is clearly a word construction rebel.

    “Simply by observing a particle in two different quantum states, you cause what is known as wave function collapse and the particle again exists in only one … location … . Therefore, measuring a particle in superposition is incredibly difficult.” Jay Bennett (Popular Mechanics)

    The Rafi mold persists with Jay.

    “In this take on the double-slit experiment, the team was able to use … heavy molecules … to create quantum interference patterns, as if they were behaving as waves and being in more than one place. The molecules were … more than 25,000 times the mass of a hydrogen atom. But as molecules get bigger, they also get less stable, and the scientists were only able to get them interfering for seven milliseconds at a time, using a newly designed piece of equipment called a matter-wave interferometer (designed to measure atoms along different paths). Even factors like the Earth’s rotation and gravitational pull had to be factored in.” – David Nield (ScienceAlert)

    “(A)s molecules get bigger, they also get less stable” can’t be the thing Dave knows that doesn’t compute. Anyway, Compton wavelength is probably cited in the paper. Seems timing differences, scaled by light speed, is measured. “Matter-wave interference” is used, instead of “matter-matter interference,” whatever that should be. More on that later, I hope. But for now I’m asking myself if it’s pretending two clumps of billions of carbon atoms are interfering, or is it pretending one clump is in two places at once? On top of that and seemingly even worse for “matter as a wave” philosophers, people are claiming interference between two different kinds of molecules is possible and that’s probably why no one is requiring the diamond lumps to be identical except through pretend-world/multiverse privilege.

  4. Fixed gravity for you. | December 16, 2023 at 10:58 am | Reply

    Everything stems pretty naturally from Einstein’s perception of “spooky action at a distance,” and that means popular royal dizzy industrial rent cartoon media will only confuse the issue with notions designed to confuse and annoy for the greater gory of the tribe. Extra-dimensionality, wormholes so fine, atoms in two places at once, Nobel prizes for aiming microwaves between target slits.

    A lot of quantum strangeness can be simulated with liquid drops on a resonant medium. Are drops good dipole models despite operating at only one resonant frequency? Is the resonant medium highlighting something about apparatus backreaction with strong field resonance? Is the medium wave limited-intensity roll-off naturally nonlinear in a way resembling tight magnetic dipole field strength? Is the medium implying superluminality in anything, or is it just revealing a backreaction feedback loop with tuned resonance?

  5. Fundamental formula aligning time, quanta, and gravity. This is my original scholarship..

  6. They need an experiment to figure that out. Um what’s a black hole again. Cause if gravity isn’t quantum then shouldn’t a black holes quantum sized points gravity not escape….so spend millions to figure out something we already know….

  7. I think there is a little too much fuss about a need to unite quantum with GR. After all they may mutually exist and not be connected at all. Take a special case of Newtonian based gravitation with has been measured at subatomic scale and that attraction is 100% accurate with Newtonian prediction to 14 decimal places. So quantum scale particles obey Newton perfectly. If Newtonian gravity need not be united with quantum why should GR? The proposed experiment is interesting but I think the answer will be as above. No wave character to gravity. But do the experiment. Let’s see the results. Graduated physics and mathematics. I see no need to unite as said above.

  8. By the way gravity waves are not the same a quantum waves and should not be confused.

  9. Fixed gravity for you. | December 18, 2023 at 12:33 pm | Reply

    Some people fight the relevance of geometry to an inverse-square (Newton-type) rule when it comes to gravity (but not quantized electrostatics), because an inverse-square rule implies an intensity variation, and an intensity, not just the essence of information theory itself, implies a quantized energy carrier density to explain it with logic and realism. Obviously Not on the mind-bending agenda, however. Agenda settlers there are probably often enough the same people who never explain that the speed of light was measured in Europe before Newton was born. The Solvay conference, fwiw, seems at times a major effort to keep the spookiness alive for the mob, and always just out of reach.

    Imo, quantum gravity waves are “stationary” to the extent that the source is “stationary” (carrier rotation phases do NOT spread out relative to a source). “Classical” (Einsteinian) waves (all phases and most notably peak phases) of gravity are *dynamic* due to *gravity effect phases (including peaks) spreading out* from their source. Both types of gravity wave are radiated gravitational energy, but quantum gravity waves are a product of quantum gravity carrier rotation along with its vectorized dipole basis effect and it has characteristics of being intrinsic to the carrier, much in the same way quantum spin is intrinsic to electrons and crates dipoles of them. Quantum gravity carriers are radiated from matter regardless of how it rotates or oscillates in space. Quantum gravity wave radiation does NOT require rotation in oblong masses or of binary mass pairs.

    Most people who wish to discount quantum gravity theoretically do so by condemning it to being some kind of “space-time” vacuum energy monopole (all pull, not dipole-like push capacity built into the carrier) which implies to me it could radiate at “c” and thus it is stuck precisely on a “light cone” or else it sits around, just waiting to do anything to help congratulate gravity theorists for being so darn smart.

    • Fixed gravity for you. | December 18, 2023 at 12:46 pm | Reply

      “much in the same way quantum spin is intrinsic to electrons and creates dipoles of them”

      … but observable in “stationary” waves, like waves in the effect of so-called “dark matter.” Huge difference in scale and the angular rotation rate lacks a complicated spectrum, maybe only two or three scales, with a galactic scale as the *shortest* wave.

      See: New Cosmological Constraints on the Nature of Dark Matter
      September 7, 2023 NAO Japan

      Some people likely believe they can match this “dark matter” effect wave pattern, existing at 30k light-year scale, to a boson condensate effect, but frankly they’re wasting everyone’s time with too much help from the usual royal suspects.

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