This tiny quantum clock packs a billion-fold energy mystery

Scientists built a tiny clock from single-electron jumps to probe the true energy cost of quantum timekeeping. They discovered that reading the clock’s output requires vastly more energy than the clock uses to function. This measurement process also drives the irreversibility that defines time’s forward direction. The insight could push researchers to rethink how quantum devices handle information.

A new experiment shows that detecting the ticks of a quantum clock uses far more energy than producing them. This dramatic imbalance reveals that observation itself is what forces time to flow forward. Credit: AI/ScienceDaily.com

A team led by the University of Oxford has uncovered an unexpected contributor to entropy in quantum timekeeping: the act of measurement itself. In findings published on November 14 in Physical Review Letters, the researchers show that the energy required to read a quantum clock is far greater than the energy needed to run it. Their results point to new challenges and opportunities for developing next-generation quantum technologies.

Traditional clocks, from pendulums to atomic oscillators, depend on irreversible processes to track time. At the quantum level, these processes become extremely weak or may barely occur at all, which makes reliable timekeeping far more complicated. Devices such as quantum sensors and navigation systems, which rely on precise timing, will need internal clocks that use energy sparingly. Until now, the thermodynamic behavior of these systems has remained largely unknown.