Researchers propose using tiny 'Ferris wheels' made from laser light to confine and rotate extremely cold atoms or molecules, potentially testing Einstein's theory of relativity on quantum scales. This method aims to observe time dilation effects in ultracold particles, where quantum properties can be precisely manipulated. The approach builds on earlier work and could reveal unexpected effects in an unexplored setting.
Albert Einstein's theories of special and general relativity, formulated in the early 1900s, showed that time can dilate for moving or accelerating clocks, causing them to tick slower than stationary ones. While these effects have been observed in large objects, Vassilis Lembessis at King Saud University in Saudi Arabia and his colleagues have devised a way to test them on atomic scales using ultracold atoms and molecules.
The proposal involves creating 'optical Ferris wheels' with laser beams to confine and rotate particles in a cylindrical shape. This builds on a 2007 method developed by Lembessis and colleagues for tuning lasers to control atomic motion. In the ultracold realm—just a few millionths of a degree above absolute zero—quantum properties and particle motion can be manipulated precisely with lasers and electromagnetic fields.
Calculations indicate nitrogen molecules are suitable candidates. By treating electron motion within them as ticks of an internal clock, researchers could detect shifts in ticking frequency as small as one part in 10 quadrillion, revealing rotational time dilation. Adjusting the laser focus would allow control of the Ferris wheel's size for testing various rotations.
Patrik Öhberg at Heriot-Watt University in the UK praised the idea: “It is important to check and confirm our understanding of physical phenomena in nature. It is when we get a surprise, something unexpected, that we need to revise our understanding and gain a deeper understanding of the universe. This work suggests an alternative way to check relativistic systems with some clear advantages compared to mechanical setups.”
Aidan Arnold at the University of Strathclyde added that the setup avoids needing impractically high speeds: “With the incredible accuracy of atomic clocks… the time change ‘felt’ by the Ferris wheel atoms should be noticeable. Also, since the accelerated atoms don’t travel very far away, there would be plenty of time to measure this change.”
Experiments with optical Ferris wheels remain rare, opening possibilities to probe the 'clock hypothesis' in quantum contexts. Challenges include preventing particles from warming up during rotation. The findings appear in Physical Review A (DOI: 10.1103/5m6c-hfqt).