State-of-the-art atomic clocks – the world’s most precise timekeepers – use lasers to measure the oscillation of atoms which takes place at a constant frequency. These clocks are so precise that if they’d been running ever since the Big Bang, they’d be off by no more than a half second.
And yet, thanks to a new technique, atomic clocks are about to become even more accurate, potentially enabling scientists to detect phenomena such as dark matter, determine the effect that gravity has on time, and find out whether time itself changes as the universe gets older.
Writing in the journal Nature, researchers from MIT have developed a new kind of atomic clock which measures atoms that have been quantumly entangled. This allows the clock to measure atoms’ vibrations with unparalleled precision.
“Entanglement-enhanced optical atomic clocks will have the potential to reach a better precision in one second than current state-of-the-art optical clocks,” said lead author Edwin Pedrozo-Peñafiel.
The ideal way to measure time would be to track the oscillations of a single atom, yet at that scale an atom will “succumb” to the rules of quantum mechanics. This means that, when measured, it will behave like a flipped coin that will give the correct probabilities only when averaged over many flips.
To overcome this issue, the research team entangled around 350 ytterbium atoms, hoping that their individual oscillations would settle into a common frequency. Given the fact that ytterbium atoms oscillate 100,000 times more often in one second than caesium atoms, scientist will now be able to measure much smaller intervals of time.
Using standard techniques, the researchers cooled and trapped the atoms in an optical cavity formed by two mirrors, and then sent a laser through the cavity, which acts like a communication link between atoms by bouncing off the mirrors and interacting with them thousands of times.
Once the atoms were entangled, the team used another laser to measure their average frequency. The new set up was able to reach desired precision four times faster than regular atomic clocks, which is crucial for measuring different types of phenomena and looking for answers to fundamental questions about the universe.
“As the universe ages, does the speed of light change? Does the charge of the electron change? That’s what you can probe with more precise atomic clocks,” said co-author Vladan Vuletic.