Ultracold Clock Sheds Light on Quantum Physics’ Impact on Time

How does time manifest for a genuine quantum entity? The most advanced clocks can rapidly address this query, enabling us to test various ways to manipulate and alter the quantum realm, thereby delving into the uncharted territories of physics.

The notion that time can shift originates from Albert Einstein’s special theory of relativity. As an object approaches the speed of light, it appears to experience time more slowly compared to a stationary observer. He expands upon this with a general theory of relativity, which demonstrates a similar temporal distortion in the presence of a gravitational field. Igor Pikovsky from the Stevens Institute in New Jersey and his team aim to uncover whether a similar effect occurs within the microscopic quantum landscape, utilizing ultra-cold clocks constructed from ions.

“The experiments we’ve performed until now have always focused on classical time, disregarding quantum mechanics,” says Pikovsky. “We’ve observed a regime where conventional explanations falter with an ion clock,” he continues.

These clocks consist of thousands of ions cooled to temperatures nearing absolute zero via laser manipulation. At such low temperatures, the quantum state of an ion and its embedded electrons can be precisely controlled through electromagnetic forces. Thus, the ticks of an ion clock are governed by the electrons oscillating between two distinct quantum states.

Since their behavior is dictated by quantum mechanics, these instruments provided an ideal platform for Pikovsky and his colleagues to investigate the interplay between relativistic and quantum phenomena on timekeeping. Pikovski mentions that they’ve identified several scenarios where this blending is evident.

One example arises from the intrinsic fluctuations inherent in quantum physics. Even at ultra-low temperatures, quantum objects cannot be completely static and instead must oscillate, randomly gaining or losing energy. Team calculations indicated that these fluctuations could lead to extended clock time measurements. Although the effect is minute, it is detectable in current ion clock experiments.

The researchers also mathematically analyzed the behavior of ions in a clock when “compressed,” resulting in “superpositions” of multiple quantum states. They found that these states are closely linked to the motion of the ions, influenced by their internal electrons. The states of ions and electrons are interconnected at a quantum level. “Typically, experiments necessitate creative methods to establish entanglements. The intriguing aspect here is that it arises organically,” explains team member Christian Sanner from Colorado State University.

Pikovski asserts that it is intuitive to think that quantum objects existing in superposition cannot simply perceive time linearly, though this effect has yet to be experimentally confirmed. He believes it should be achievable in the near future.

Team member Gabriel Solch from the Stevens Institute of Technology mentions that the next step is incorporating another crucial aspect of modern physics: gravity. Ultra-cold clocks can currently detect temporal extensions caused by significant variations in the Earth’s gravitational pull, such as when elevated by a few millimeters, but the exact integration of these effects with the intrinsic quantum characteristics of the clock remains an unresolved question.

“I believe it is quite feasible with our existing technology,” adds David Hume from the U.S. National Institute of Standards and Technology, Colorado. He highlights that the primary challenge is to mitigate ambient disturbances affecting the clock to ensure it doesn’t overshadow the effects suggested by Pikovsky’s team. Successful experiments could pave the way for exploring unprecedented physical phenomena.

“Such experiments are thrilling because they create a platform for theories to interact in a domain where they could yield fresh insights,” remarks Alexander Smith at St. Anselm College, New Hampshire.