A new study proposes that highly precise optical atomic clocks could reveal the quantum nature of time, suggesting time may exhibit quantum phenomena like superposition and entanglement.

If a clock’s motion is governed by quantum mechanics, its passage of time can become entangled and exist in multiple states, extending relativistic time effects into the quantum realm.

The approach uses ultra-precise trapped-ion clocks and quantum techniques such as squeezed states to reveal quantum signatures of time in laboratory experiments.

The paper detailing these ideas appears in Physical Review Letters, authored by Igor Pikovski and colleagues from Stevens Institute of Technology and collaborating institutions.

Among observable predictions, the vacuum shift could be detectable with near-future capabilities, while deeper quantum Doppler effects may be too small to observe currently.

Realizing these effects demands extreme isolation from vibrations, temperature fluctuations, and electromagnetic interference, and interpreting results will be complex.

An experimental pathway envisions aluminum-ion clocks in a 20 MHz trap with strong squeezing and long coherence times to observe clock-motion entanglement and related frequency shifts, though deeper quantum Doppler effects remain out of reach now.

Even without confirming quantum time, advances in clock technology are expected to enhance navigation, gravitational sensing, quantum computing, and communications.

The work predicts measurable quantum effects at near-zero temperature due to quantum motion fluctuations, including a vacuum-induced second-order Doppler shift potentially causing a fractional frequency shift on the order of 5×10^-9 in a megahertz trap.

Researchers caution that they do not claim time is quantum; they call for repeat experiments, cross-clock comparisons, and refined models to validate findings.

Atomic clocks are the most precise time standards, using atomic transitions to enable navigation, communications, and data synchronization.

Experiments would use trapped ions like aluminum or ytterbium at ultra-cold temperatures, leveraging quantum control techniques developed for metrology and quantum computing.