According to a theoretical study by Dartmouth College, Saint Anselm College, and Santa Clara University, a quantum mechanics phenomenon known as superposition can affect the measurement of time in high-precision clocks.

Research describing the effect shows that superposition – the ability of one atom Existing in more than one state at the same time – leads to a correction of the atomic clocks known as “quantum time dilation”.

The research, published today (October 23, 2020) in the journal *Communication with nature*considers quantum effects beyond Albert Einstein’s theory of relativity to make a new prediction about the nature of time.

“Whenever we’ve made better watches, we’ve learned something new about the world,” said Alexander Smith, assistant professor of physics at Saint Anselm College and associate professor at Dartmouth College who led the research as a junior fellow at the Dartmouth Society of Fellows. “Quantum time dilation is a consequence of both quantum mechanics and Einstein’s theory of relativity and therefore offers a new way of testing basic physics at its intersection.”

In the early 1900s, Albert Einstein presented a revolutionary picture of space and time by showing that the time a watch experiences depends on how fast it moves – as the speed of a watch increases, the speed decreases, that makes it tick. This was a radical departure from Sir Isaac Newton’s absolute concept of time.

Quantum mechanics, the theory of motion that governs the atomic realm, enables a clock to move as if it were moving at two different speeds at the same time: a quantum “superposition” of speeds. The research paper takes this possibility into account and provides a probabilistic theory of time measurement that led to the prediction of quantum time dilation.

To develop the new theory, the team combined modern techniques from quantum information science with a theory developed in the 1980s that explains how time could arise from a quantum theory of gravity.

“Physicists have tried for decades to account for the dynamics of time in quantum theory,” said Mehdi Ahmadi, a lecturer at Santa Clara University who co-authored the study. “In our work, we predict corrections to the relativistic time dilation that result from the fact that the clocks used to measure this effect are quantum mechanical in nature.”

Just as carbon dating relies on decaying atoms to determine the age of organic objects, the lifespan of an excited atom acts as a clock. If such an atom moves at different speeds in a superposition, its lifetime increases or decreases depending on the type of superposition relative to an atom moving at a certain speed.

The correction to the life of the atom is so small that it would be impossible to measure in terms that make sense on a human scale. However, the ability to account for this effect could allow a test of quantum time dilation using the most advanced atomic clocks.

Just as the usefulness of quantum mechanics for medical imaging, computing, and microscopy was difficult to predict when this theory was developed in the early 1900s, it is too early to imagine the full practical implications of quantum time dilation.

Reference: October 23, 2020, *Communication with nature*.

DOI: 10.1038 / s41467-020-18264-4