Researchers in Boulder built a new clock that is more precise and accurate than any clock in the world.
The discovery has implications for exploring fundamental physics questions, propelling new technologies and even redefining time. The clock was built by researchers at JILA, a joint institute of the National Institute of Standards and Technology and the University of Colorado Boulder.
“There’s an international definition of time, and we want clocks like this to start to play a role because eventually the time will be redefined based on these types of research clocks,” NIST physicist and CU Boulder professor Jun Ye said.
The international definition of time is how the world counts a second. The existing measurement of a second was adopted in 1967. Ye said scientists worldwide are considering redefining the second based on the newest generation of atomic clocks like the one he and his team created.
“I think it gives you the sense of a thrill when you get to be the first one to see certain phenomenon that was not predicted or known, especially when things didn’t work out as well as theory would have predicted,” Ye said. “You make some discoveries, which is truly what we live for.”
The clock is roughly 20 feet wide, 20 feet long and 10 feet tall. It contains a large, stainless steel vacuum chamber. It’s an optical atomic clock, meaning it uses light waves from lasers and the frequency of atoms inside the vacuum to measure a second. The clock relies on the natural property of the atom’s frequency to be accurate. Atoms vibrate at a constant frequency, and the vibration can be used to measure time.
“It’s referenced to a kind of inherent quantum mechanical property of these atoms,” CU Boulder graduate student Alexander Aeppli said.
Existing-generation microwave atomic clocks shine microwaves on atoms to measure the second. This new wave of optical atomic clocks illuminates atoms with visible light waves, which have a much higher frequency, to count out the second more precisely.
Optical atomic clocks are expected to deliver much higher accuracy for international timekeeping — potentially losing just one second every 30 billion years. Ye’s been building clocks and making new discoveries for 30 years.
“It’s also human curiosity,” Ye said. “Where is the limit, where does nature allow me to go to find out about the time? As you push further oftentimes when you see what previously was a limit was just a misunderstanding of the physics. So it’s a learning opportunity.”
Ye said students like Aeppli learn in this environment and go out and drive the future of the industry. There’s an exciting sense of uncertainty about what physics will teach them next.
“There isn’t a limit yet, we haven’t seen a limit on the accuracy,” Aeppli said. “And so to make another step forward and improve the accuracy of these clocks is encouraging for the field. Of course, I think that the most interesting thing will actually be using this clock.”
One application is GPS, which uses accurate atomic clocks in navigation.
“If you, for example, put our clock into a GPS satellite you’d be able to precisely tell where you are much better and much faster than you can currently,” Aeppli said.
Accurate clocks are also critically important in space travel, where tiny errors in timekeeping could cause astronauts to stray many miles off course. Accuracy could also lead to breakthroughs in quantum computers, which use the manipulation of atoms to perform.
Next, the team plans to compare the new clock with other clocks in the Boulder area to look at frequencies and ensure the clocks are performing well.
“We need to make sure we can build clocks very accurately, very precisely and repeatably,” Aeppli said. “So this is a really important way to test our clock and show that this technology can be used in the redefinition of the second.”
Ye said it will take a few years for scientists around the world to evaluate their new atomic clocks. A redefinition of time will take consensus, scientific validity and verification of the clock against other clocks.
“Time will continue, and ordinary citizens, they will hardly ever tell that time has been redefined in a different way,” Ye said. “But as atomic physicists, we actually take that moment very, very seriously and we have to be ready for when our atomic clock will be relied upon to give you a worldwide time stamp.”
