World-first nuclear clock prototype could outperform atomic clocks

Amazing stuff! Exciting! What comes next? Anti matter clocks? (just kidding)

It took only 21 years from proposal to realization!

"... Nuclear clocks work on a similar principle, except instead of measuring the vibrations of a whole atom, they focus in on just the nucleus. ...
The nucleus has a much higher number of “ticks” per second, breaking down the second into even smaller chunks for more accurate timekeeping. As a bonus, it’s more stable against disturbances like electromagnetism that can mess up these measurements. ...

The problem is, a nuclear clock would normally require a much stronger laser than in atomic clocks – except for thorium-229. The nucleus of this atom has two quantum states that are much closer together in energy level, so a smaller kick is needed to jump between them.

Back in April, researchers at JILA finally managed to figure out the exact value of that energy difference, and then actively switched thorium nuclei between them for the first time. Doing so required an ultraviolet laser, instead of the usual infrared light used for atomic clocks. ...

Now the team has built on that work to demonstrate all the components needed to create a nuclear clock. A series of infrared laser pulses are fired at a xenon gas, which produces UV light in a predictable pattern. This UV light is then beamed at thorium nuclei suspended in a tiny crystal, to excite the protons and neutrons in there. An "optical frequency comb" counts the UV wave cycles to make the ultra-precise measurements of time. ..."

"

• Nuclear clocks would measure time based on changes inside an atom's nucleus, which would make them less sensitive to external disturbances and potentially more accurate than atomic clocks.
• These clocks could lead to improved timekeeping and navigation, faster internet speeds, and advances in fundamental physics research.
• Scientists have demonstrated key components of a nuclear clock, such as precise frequency measurements of an energy jump in a thorium-229 nucleus.

..."

"... But it is very hard to create a nuclear clock. To make energy jumps, most atomic nuclei need to be hit by coherent X-rays (a high-frequency form of light) with energies much greater than those that can be produced with current technology. So scientists have focused on thorium-229, an atom whose nucleus has a smaller energy jump than any other known atom, requiring ultraviolet light (which is lower in energy than X-rays).

In 1976, scientists discovered this thorium energy jump, known as a “nuclear transition” in physics language. In 2003, scientists proposed using this transition to create a clock, and but they didn’t directly observe it until 2016. Earlier this year, two different research teams used ultraviolet lasers they created in the lab to flip the nuclear “switch” and measure the wavelength of light needed for it. ..."

From the abstract:

"Optical atomic clocks use electronic energy levels to precisely keep track of time. A clock based on nuclear energy levels promises a next-generation platform for precision metrology and fundamental physics studies. Thorium-229 nuclei exhibit a uniquely low-energy nuclear transition within reach of state-of-the-art vacuum ultraviolet (VUV) laser light sources and have, therefore, been proposed for construction of a nuclear clock. However, quantum-state-resolved spectroscopy of the 229mTh isomer to determine the underlying nuclear structure and establish a direct frequency connection with existing atomic clocks has yet to be performed. Here, we use a VUV frequency comb to directly excite the narrow 229Th nuclear clock transition in a solid-state CaF2 host material and determine the absolute transition frequency. We stabilize the fundamental frequency comb to the JILA 87Sr clock2 and coherently upconvert the fundamental to its seventh harmonic in the VUV range by using a femtosecond enhancement cavity. This VUV comb establishes a frequency link between nuclear and electronic energy levels and allows us to directly measure the frequency ratio of the 229Th nuclear clock transition and the 87Sr atomic clock. We also precisely measure the nuclear quadrupole splittings and extract intrinsic properties of the isomer. These results mark the start of nuclear-based solid-state optical clocks and demonstrate the first comparison, to our knowledge, of nuclear and atomic clocks for fundamental physics studies. This work represents a confluence of precision metrology, ultrafast strong-field physics, nuclear physics and fundamental physics."

World-first nuclear clock prototype could outperform atomic clocks "Atomic clocks are the most accurate timekeepers we have, losing only seconds across billions of years. But apparently that’s not accurate enough – nuclear clocks could steal their thunder, speeding up GPS and the internet, among other things. Now, scientists have built and tested the first prototype nuclear clock."

Major Leap for Nuclear Clock Paves Way for Ultraprecise Timekeeping

Progress on nuclear clocks shows the benefits of escaping from scientific silos "Nuclear clocks might soon rival the best atomic ones as supremely accurate timekeepers — a testament to the value of both competition and cooperation in research."

Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock (no public access)

Using an extremely high-powered laser, scientists can excite the thorium-229 nucleus, which is the core of a future nuclear clock.