Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Looking at quantum gravity in a mirror

19.03.2012
Einstein's theory of gravity and quantum physics are expected to merge at the Planck-scale of extremely high energies and on very short distances.

At this scale, new phenomena could arise. However, the Planck-scale is so remote from current experimental capabilities that tests of quantum gravity are widely believed to be nearly impossible.


This is an illustration of a laser pulse used to probe a mirror for possible quantum gravitational effects. Credit: Jonas Schmoele, VCQ, University of Vienna

Now an international collaboration between the groups of Caslav Brukner and Markus Aspelmeyer at the University of Vienna and Myungshik Kim at Imperial College London has proposed a new quantum experiment using Planck-mass mirrors. Such an experiment could test certain predictions made by quantum gravity proposals in the laboratory. The findings will be published this week in Nature Physics.

A long-standing challenge

The search for a theory that unifies quantum mechanics with Einstein's theory of gravity is one of the main challenges in modern physics. Quantum mechanics describes effects at the scale of single particles, atoms and molecules. Einstein's theory of gravity, on the other hand, is typically relevant for large masses. It is widely expected that phenomena stemming from a unified theory of quantum gravity will become evident only at the so-called Planck-scale of extremely high energies or extremely small distances. The Planck-length is 1.6 x 10-35 meters: This is so small that if one were to take this scale to be 1 meter, then an atom would be as large as the entire visible Universe! Similarly, the Planck-energy is so large that even the Large Hadron Collider in CERN only reaches an insignificantly tiny fraction of this energy, and a particle accelerator would need to be of astronomical size to get even close to the Planck-Energy. This scale is also described by the Planck-mass: A piece of dust weights about that much, which is truly heavy compared to single atoms, and quantum phenomena are typically considered unobservable for such masses. The Planck-scale is therefore so remote from current experimental capabilities that tests of quantum gravity proposals are widely believed to be nearly impossible. However, physicists have now found a way to probe some predictions of quantum gravity proposals in the laboratory by looking at quantum effects in Planck-mass quantum systems.

The sequence makes the difference

In quantum mechanics it is impossible to know where a particle is and how fast it is moving at the same time. Nevertheless, it is possible to make two subsequent measurements: a measurement of the particle's position followed by a measurement of its momentum, or vice-versa. In quantum physics the two different measurement sequences produces different experimental results. According to many theories of quantum gravity, this difference would be altered depending on the mass of the system, since the Planck-length puts a fundamental limit on measurements of distances. The team of physicists have now shown that although such modifications would be very small, they could be verified by using very massive quantum systems in the laboratory. Such an experiment could therefore test some of the proposals for quantum gravity.

Probing new theories with moving mirrors

The main idea is to use a laser pulse to interact four times with a moving mirror to probe exactly the difference between measuring first position after measuring momentum as compared to measuring momentum after measuring the position. By timing and engineering the interactions very precisely, the team have shown it is possible to map the effect onto the laser pulse and to read it out with quantum optical techniques. "Any deviation from the expected quantum mechanical result would be very exciting", says Igor Pikovski, the lead author of the work, "but even if no deviation is observed, the results can still help in the search for possible new theories". Some theoretical approaches to quantum gravity indeed predict different outcomes for the experiment. The scientists thus show how to probe these yet unexplored theories in a laboratory without using high-energy particle accelerators and without relying on rare astrophysical events.

Publication: Probing Planck-scale physics with quantum optics. I. Pikovski, M. R. Vanner, M. Aspelmeyer, M. S. Kim and CASLAV Brukner. Nature Physics (2012) DOI: 10.1038/NPHYS2262

Igor Pikovski | EurekAlert!
Further information:
http://www.univie.ac.at

More articles from Physics and Astronomy:

nachricht Hope to discover sure signs of life on Mars? New research says look for the element vanadium
22.09.2017 | University of Kansas

nachricht Calculating quietness
22.09.2017 | Forschungszentrum MATHEON ECMath

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>