Search FQXi


RECENT FORUM POSTS

thuy lien: "The faction in Bannerlord: Battania King: ‘Caladog’ -partially..." in Collapsing Physics: Q&A...

thuy lien: "Good article, thanks for sharing. hell let loose metal gear survive far..." in Blurring Causal Lines

Boyd Bunton: "Nice share! I am no able ti skip this moment without appreciating you...." in Podcast Up: Interacting...

Greg Fantle: "Brush your hair! You look like a homeless person." in The Complexity Conundrum

kurt stocklmeir: "shape of time and space around mass vibrates - some times the shape of time..." in Alternative Models of...

Gary Simpson: "Still waiting for essays to be posted. There are only 5 weeks or so left..." in What Is...

Boyd Bunton: "Its absolutely very helpful put up about the subject. All readers can be..." in Podcast Up: Interacting...

Georgina Woodward: "John, I reported your post as inappropriate as it is mostly irrelevant to..." in What Is...


RECENT ARTICLES
click titles to read articles

The Complexity Conundrum
Resolving the black hole firewall paradox—by calculating what a real astronaut would compute at the black hole's edge.

Quantum Dream Time
Defining a ‘quantum clock’ and a 'quantum ruler' could help those attempting to unify physics—and solve the mystery of vanishing time.

Our Place in the Multiverse
Calculating the odds that intelligent observers arise in parallel universes—and working out what they might see.

Sounding the Drums to Listen for Gravity’s Effect on Quantum Phenomena
A bench-top experiment could test the notion that gravity breaks delicate quantum superpositions.

Watching the Observers
Accounting for quantum fuzziness could help us measure space and time—and the cosmos—more accurately.


FQXI ARTICLE
December 15, 2017

Sounding the Drums to Listen for Gravity’s Destructive Effect on Quantum Phenomena
A bench-top experiment could test the notion that gravity breaks delicate quantum superpositions.
by Steven Ashley
FQXi Awardees: Andrew Briggs
August 8, 2017
Bookmark and Share


Good Vibrations
Inside this cryogenic vacuum chamber tiny ceramic "trampolines"
could ring out news of any undiscovered interactions between
gravitation and quantum mechanics.

Credit: Edward Laird
Like jars of peanut butter, nature’s basic rules come in both smooth and chunky-style.

General relativity, which smoothly accounts for gravity and its effects on large objects ranging in size from galaxies to fly ash, describes events as continuous and deterministic so that every cause matches up to a specific, local effect. Chunky-style quantum mechanics, by contrast, accounts for the electromagnetic and nuclear forces and their effects on small things like atoms in a discontinuous, step-wise fashion.

Unlike smooth and chunky peanut butter, however, both of these fully validated conceptions of physical reality do not typically mix. At the borderline between large and small objects, the writ of one set of nature’s rules rather mysteriously falls away in favor of the other, a phenomenon that makes the ’mesoscale’-size range one of the least understood, least explored areas in physics. Yet research physicists led by Andrew Briggs at the University of Oxford, in the UK, are soon to start reaching into this terra incognita medio in hopes of finding clues that might help reconcile quantum mechanics with gravitation.

Quantum phenomena generally go unseen in the macro world, as nanoparticles’ delicate quantum properties almost always get smeared out through interactions with larger-scale objects. But under the right conditions odd effects like quantum superpositions—the ability for an atom to be in multiple energy states at once, for instance—can proliferate sufficiently to appear where we can observe them.

The oscillators operate
like tiny trampolines
or drums.
- Natalia Ares
It’s no surprise then that recent advances in nanotechnology and cryogenic engineering have led Briggs, and his Oxford co-investigators, Edward Laird and Natalia Ares, to become interested in the quantum manipulation of macroscopic mechanical systems. They have constructed a bench-top lab apparatus that they hope will be able to achieve the extremely sensitive measurements needed to pick out gravity’s effect on quantum superposition—if it has one. Their project is funded by a grant of almost $115,000 from the Foundational Questions Institute.

The set-up involves tiny, but still macroscale, oscillators—extremely thin, millimeter-size membranes of stiff silicon nitride ceramic—placed inside a vacuum-filled cavity. The oscillators operate like "tiny trampolines or drums," says Ares. Once stimulated to vibrate, they ring true for many seconds like tuning forks, she says.

The plan is to cool the oscillators using a dilution-refrigeration system to just around 10 to 15 milliKelvin above absolute zero. At this low temperature, enough energy has been removed from the oscillators to make mechanical vibrations grow nearly quiet. In this quiet environment, the researchers hope to detect a competition between two effects: The electrical interactions between neighboring atoms favors creating a superposition, but gravity will try to collapse it. This provides a platform on which to study the interplay between gravitational and quantum physics.

Gravitational Kicks

The theory the team is testing is based on the work of team member Gerard Milburn, a quantum physicist at the University of Queensland, in Brisbane, Australia. It predicts that gravity forces the atoms’ superposition to collapse into definite states. "Because the gravitational force between atoms is so tiny, this effect would not yet have been detected," Ares explains. "This constant collapse of superpositions applies tiny random kicks to the atomic positions, which heats up the material."

The fact that the oscillators act as drums gives a way to sensitively measure the predicted heating. The temperature rise causes the drum to vibrate a tiny bit more, which in principle could be detected. "We hope to monitor the heating due to these gravitational kicks, although measuring that heat will be difficult because it will require an extremely low noise level," Laird says.

Even if the experiment is successful, Laird notes, the best way to check the results would be to carry out similar experiments in orbit, where there will be less background vibration.

Jörg Schmiedmayer, a quantum physicist at the Technical University of Vienna, in Austria, says it will be important to see if nano-mechanical systems can yield large enough gravitational effects to be measurable. "In most of these schemes, any quantum effects are destroyed extremely easily," says Schiedmayer. "Hopefully, their instrumentation will be sensitive enough to produce a clear-cut result."

Comment on this Article

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!
  • Please enter the text of your post, then click the "Submit New Post" button below. You may also optionally add file attachments below before submitting your edits.

  • HTML tags are not permitted in posts, and will automatically be stripped out. Links to other web sites are permitted. For instructions on how to add links, please read the link help page.

  • You may use superscript (10100) and subscript (A2) using [sup]...[/sup] and [sub]...[/sub] tags.

  • You may use bold (important) and italics (emphasize) using [b]...[/b] and [i]...[/i] tags.

  • You may also include LateX equations into your post.

Insert LaTeX Equation [hide]

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview



preview equation
clear equation
insert equation into post at cursor


Your name: (optional)






Recent Comments


Bee Bagshop adalah toko tas online yang berdiri sejak tahun 2013 yang telah berpengalaman menjual tas sekolah dengam model yang trendy dan kekinian agar para konsumen dari berbagai wilayah di Indonesia bisa mendapatkan tas dengan harga ekonomis dan terjangkau agar tetap gaya. Koleksi tas selengkapnya lihat di blog Jual Tas Sekolah Online


Tom,

Thanks, I was able to download the attachment but have been combatting a virus this afternoon and the reply box isn't showing the anti-robot function. This panel has a separate 'I'm not a robot' quiz and maybe that will reactivate things. Onward through the fog! jrc


John, I apologize. I didn't know the site was so restricted. I knew you had to register to join, but I thought that was to facilitate communications among researchers, not to keep the public out.

I guess I should have my own web site, but I'm too lazy to maintain it, and too broke to pay someody to do it. I'll figure something out.

Meanwhile, I have attached an excerpt--the introduction--which lays out the main idea and purpose. If anyone is sufficiently interested, I will...

read all article comments

Please enter your e-mail address:
Note: Joining the FQXi mailing list does not give you a login account or constitute membership in the organization.