Redefining clock time using quantum light clocks

Atomic clocks are the most precise means to measure time. However, their precision has reached a point where they resolve gravitational time dilation on smaller scales than their own extensions. Redefining time based on these clocks has become an important point of quantum research.

Fuentes et al. focused on developing a consistent description of a clock model compatible with both quantum mechanics and general relativity.

“In the presence of the gravitational field of the earth, a clock at one height location will tick at a different rate than a clock at a different height,” said Ivette Fuentes. “We used light to study this challenge of building a clock at the interface of quantum mechanics and general relativity.”

The quantum light clock model was chosen because theoretical methods in quantum field theory in curved space enable the consistent description of a quantum system under the effects of a gravitational field, such as that produced by the Earth or a black hole.

Vertical and horizontal orientations of a quantized electromagnetic field confined in a rectangular cavity located at a fixed distance from a spherical body were evaluated. Results showed that a vertically oriented, extended light clock of 20 cm resolved gravitational time dilation on or below its own length scale. A reference point for time measurements within the clock must be specified.

“As atomic clocks are now close to the resolution of gravitational time dilation on the length scale of their size, the accuracy of time measurement approaches a fundamental boundary that must be taken seriously,” said Fuentes.

Source: “Gravitational time dilation in extended quantum systems: The case of light clocks in Schwarzschild spacetime,” by Tupac Bravo, Dennis Rätzel, and Ivette Fuentes, AVS Quantum Science (2023). The article can be accessed at https://doi.org/10.1116/5.0123228 .