Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Physicists from Ulm put Einstein to the test - Atomic clock on space-time voyage: a quantum-mechanical twin paradox


Ulm's most famous son, Albert Einstein, is regarded as one of the founding fathers of modern physics. In particular, his theories of general and special relativity as well as his fundamental contributions to quantum mechanics continue to have significance to this day. Nonetheless, the genius of his century struggled throughout his life with the philosophical consequences of quantum mechanics.

Physicists from Einstein's hometown Ulm and from Hannover have taken on the challenge of investigating the intersections of the theory of relativity and quantum mechanics. For this very purpose, they draw on the famous twin paradox that is a direct consequence of the theory of relativity.

Graphic illustration of the quantum-mechanical variant of the twin paradox

graph: Ulm University

The physicists from Ulm who contributed to the publication (from left to right): Alexander Friedrich, Fabio Di Pumpo, Albert Roura, Christian Ufrecht und Dr. Enno Giese

photo: Eberhardt/Uni Ulm

In the journal Science Advances, the researchers have now published the theoretical foundations for an experiment that tests a quantum-mechanical variant of the twin paradox. Particularly suited for a realisation of the experiment is the 10-metre-high atomic fountain currently under construction in Hannover.

One of the fundamental challenges of physics is the reconciliation of Einstein's theory of relativity and quantum mechanics. The necessity to critically question these two pillars of modern physics arises, for example, from extremely high-energy events in the cosmos, which so far can only ever be explained by one theory at a time, but not both theories in harmony.

Researchers around the world are therefore searching for deviations from the laws of quantum mechanics and relativity that could open up insights into a new field of physics.

For the publication at hand, scientists from Ulm University and Leibniz University Hannover have taken on the twin paradox known from Einstein's special theory of relativity. This thought experiment revolves around a pair of twins: While one brother travels into space, the other remains on Earth. Consequently, for a certain period of time, the twins are moving along different paths in space.

The result when the pair meets again is quite astounding: The twin who has been travelling through space has aged much less than his brother who stayed at home. This phenomenon is explained by Einstein's description of time dilation: Depending on the speed and where in the gravitational field two clocks move relative to each other, they tick at different rates.

For the publication in Science Advances, the authors assumed a quantum-mechanical variant of the twin paradox with only a single 'twin'. Thanks to the superposition principle of quantum mechanics, this 'twin' can move along two paths at the same time. In the researchers' thought experiment, the twin is represented by an atomic clock.

'Such clocks use the quantum properties of atoms to measure time with high precision. The atomic clock itself is therefore a quantum-mechanical object and can move through space-time on two paths simultaneously due to the superposition principle.

Together with colleagues from Hannover, we have investigated how this situation can be realised in an experiment,' explains Dr. Enno Giese, research assistant at the Institute of Quantum Physics in Ulm. To this end, the researchers have proposed an experimental setup for this scenario based on a quantum-physical model.

The 10-metre-high 'atomic fountain', which is currently being built at Leibniz University Hannover, plays an essential role in this endeavour. In this atomic interferometer and with the use of quantum objects such as the atomic clocks, researchers can test relativistic effects – including the time dilation causing in the twin paradox.

'In an experiment, we would send an atomic clock into the interferometer. The crucial question is then: Under what conditions can a time difference be measured after the experiment, during which the clock moves simultaneously along two paths after all,' explains Sina Loriani from the Institute of Quantum Optics at Leibniz University Hannover.

The theoretical preliminary work of the physicists from Ulm and Hannover is very promising: As described, they have developed a quantum-physical model for the atomic interferometer, which factors in the interaction between lasers and atoms as well as the movement of the atoms – while also taking into account relativistic corrections.

'With the help of this model, we can describe a "ticking" atomic clock that moves simultaneously along two paths in a spatial superposition. Moreover, we demonstrate that an atomic interferometer, such as the one being built in Hannover, can measure the effect of the special relativistic time dilation on an atomic clock,' recaps Alexander Friedrich, a doctoral researcher at the Institute of Quantum Physics in Ulm.

Based on their theoretical considerations, the researchers can already make the assumption that a single atomic clock behaves as predicted in by the twin paradox: The theory of relativity and quantum mechanics are therefore indeed reconcilable in this particular scenario. The influence of gravity as assumed by other groups, however, does not seem verifiable in this specific case.

The theoretically described experiment is anticipated to be put to the test in the new atomic interferometer in Hannover in a few years' time.
In practice, the scientists' findings could help to improve applications based on atomic interferometers such as navigation, or acceleration and rotation measurements.

The research conducted by the physicists from Ulm and Hannover is the result of the project QUANTUS and the Collaborative Research Centre DQ-mat (Hannover). Recently, Professor Wolfgang Schleich, Director of the Institute of Quantum Physics, succeeded in bringing a new institute of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; short: DLR) to Ulm. The new DLR QT institute is dedicated to the development of quantum-technologies for space applications and will continue the presented line of work together with its concurrently founded sister institute DLR SI in Hannover.

At Ulm University, quantum technology is one of the designated strategic development areas. At the Center for Integrated Quantum Science and Technology (IQST), interdisciplinary researchers from Ulm and Stuttgart transfer findings from quantum technology physics into practice: They develop novel sensors and optimise imaging processes, among other things. In this context, Ulm University established the new research field of quantum biosciences.

Wissenschaftliche Ansprechpartner:

Dr. Enno Giese, Institut für Quantenphysik der Universität Ulm: Tel.: 0731/50-22782,
Sina Leon Loriani Fard, Institut für Quantenoptik der Leibniz Universität Hannover:


Sina Loriani, Alexander Friedrich, Christian Ufrecht, Fabio Di Pumpo, Stephan Kleinert, Sven Abend, Naceur Gaaloul, Christian Meiners, Christian Schubert, Dorothee Tell, Étienne Wodey, Magdalena Zych, Wolfgang Ertmer, Albert Roura, Dennis Schlippert, Wolfgang P. Schleich, Ernst M. Rasel and Enno Giese. Interference of Clocks: A Quantum Twin Paradox. Science Advances, Vol. X, No. Z,axx8966 (2019) DOI 10.1126/sciadv.aax8966

Annika Bingmann | idw - Informationsdienst Wissenschaft
Further information:

Further reports about: Atomic QUANTUM atomic clock quantum mechanics quantum technology twin paradox

More articles from Physics and Astronomy:

nachricht The spin state story: Observation of the quantum spin liquid state in novel material
09.07.2020 | Tokyo University of Science

nachricht TU Graz experimental physicists study steel on board the ISS
09.07.2020 | Technische Universität Graz

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 spin state story: Observation of the quantum spin liquid state in novel material

New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices

Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

Im Focus: Gentle wall contact – the right scenario for a fusion power plant

Quasi-continuous power exhaust developed as a wall-friendly method on ASDEX Upgrade

A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Latest News

The spin state story: Observation of the quantum spin liquid state in novel material

09.07.2020 | Physics and Astronomy

New method for simulating yarn-cloth patterns to be unveiled at ACM SIGGRAPH

09.07.2020 | Information Technology

Stress testing 'coral in a box'

09.07.2020 | Life Sciences

Science & Research
Overview of more VideoLinks >>>