It's not exactly a clock yet but a prototype has been unveiled that will eventually lead to an ultraprecise clock. The prototype is not yet used to measure time. So it technically should be called a “frequency standard,”
Whereas atomic clocks measure time based on electrons jumping between energy levels in atoms, nuclear clocks’ timekeeping would depend on the energy levels of atomic nuclei. A certain frequency of laser light is needed for an atom or an atomic nucleus to make such a jump. The wiggling of that light’s electromagnetic waves can be used to mark time.
Every clock needs a timekeeper – for example the regular swinging motion of the pendulum in a pendulum clock. Today, high precision clocks use the oscillation of electromagnetic waves for this purpose; the oscillations of a laser beam are counted to measure time intervals. However, the frequency of a laser can change slightly over time, and so its frequency has to be to be readjusted. That's why, in addition to the laser, you need a quantum system that reacts extremely selectively to a very specific laser frequency.
Nuclear clocks would keep time using a variety of the element thorium, called thorium-229. Most atomic nuclei make energy leaps that are too large to be triggered by a tabletop laser. But thorium-229 has two energy levels that are close enough to each other that the transition between those two levels could serve as a clock.
Now, researchers have precisely determined the frequency of the light needed to set off that jump. It’s 2,020,407,384,335 kHz. Importantly, the measurement has an uncertainty of 2 kilohertz. That’s more than a million times the precision of the best previous measurement. And it’s more than a billion times the precision to which that frequency was known just over a year ago, highlighting multiple back-to-back developments.
Whereas atomic clocks measure time based on electrons jumping between energy levels in atoms, nuclear clocks’ timekeeping would depend on the energy levels of atomic nuclei. A certain frequency of laser light is needed for an atom or an atomic nucleus to make such a jump. The wiggling of that light’s electromagnetic waves can be used to mark time.
Every clock needs a timekeeper – for example the regular swinging motion of the pendulum in a pendulum clock. Today, high precision clocks use the oscillation of electromagnetic waves for this purpose; the oscillations of a laser beam are counted to measure time intervals. However, the frequency of a laser can change slightly over time, and so its frequency has to be to be readjusted. That's why, in addition to the laser, you need a quantum system that reacts extremely selectively to a very specific laser frequency.
Nuclear clocks would keep time using a variety of the element thorium, called thorium-229. Most atomic nuclei make energy leaps that are too large to be triggered by a tabletop laser. But thorium-229 has two energy levels that are close enough to each other that the transition between those two levels could serve as a clock.
Now, researchers have precisely determined the frequency of the light needed to set off that jump. It’s 2,020,407,384,335 kHz. Importantly, the measurement has an uncertainty of 2 kilohertz. That’s more than a million times the precision of the best previous measurement. And it’s more than a billion times the precision to which that frequency was known just over a year ago, highlighting multiple back-to-back developments.
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