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 NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

nachricht Pluto's hydrocarbon haze keeps dwarf planet colder than expected
16.11.2017 | University of California - Santa Cruz

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: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>