Joshua Howgego: How would you make a nuclear clock?
Jun Ye: People have made nuclear clocks for a long time. The conventional way is to sparkle microwaves onto iotas, like calcium or rubidium, to make their electrons flip from one quantum state - known as twist - to one more at standard stretches. This flipping is the tick of the clock. In the tickers I make, the standard is something very similar. However, we use laser light and sparkle it on strontium particles, so electrons go through energy changes between two stable orbitals - and that is the tick.
How great is your clock?
There are three significant execution measurements. First: how exact is your clock, or how well might you at any point method time? Second: how reproducible is it? This alludes to whether you can get a similar sort of estimation following a day, seven days, a year. Third: how precise is it? Is it a period that everybody can concur upon, after all methodical impacts have been appropriately represented? This is unique in relation to accuracy.
An all-optical atomic clock, recently demonstrated by researchers at the US National Institute of Standards and Technology (NIST; Gaithersburg, MD), produces about 1 quadrillion "ticks" per second and promises to be as much as 1000 times more accurate than the world's current standard in time measurement-cesium-based microwave atomic clocks.
An all-optical atomic clock, recently demonstrated by researchers at the US National Institute of Standards and Technology (NIST; Gaithersburg, MD), produces about 1 quadrillion "ticks" per second and promises to be as much as 1000 times more accurate than the world's current standard in time measurement-cesium-based microwave atomic clocks.
Our optical clock, as well as those being developed by other groups around the world, should give scientists an even finer-grained view of the physical world, much as precision spectroscopy in the past 50 years has opened the door to an improved understanding of many fundamental aspects of atoms and molecules, says NIST physicist Scott.
For the past 50 years, microwave atomic clocks have set standards for precision time and frequency metrology. Today, the most precise clocks are based on a natural atomic resonance of the cesium atom—the atomic equivalent of a pendulum. For example, NIST-F1, one of the world's most accurate time standards based on microwave atomic clocks, neither gains nor loses a second in 20 million years. The new clock, however, is designed to neither gain nor lose a second in 3 billion years.
The optical clock at NIST relies on a combination of advances in physics: the trapping and cooling of atoms and ions with lasers; frequency-stabilized lasers; and a new optical frequency "comb" that uses a second laser with nonlinear optical fibers to provide a simple, direct, and exact linkage between microwave and optical frequencies.
The researchers built their optical clock with a stable continuous-wave (CW) laser oscillator that is frequency doubled and locked to a narrow ultraviolet (282-nm) transition of a single, trapped and laser-cooled mercury ion (Hg+). Once stabilized, the frequency of the laser light was coherently divided down to lower frequencies with a second mode-locked laser that ultimately produced an electronic output at a frequency of 1 GHz. The envelope of the pulse train was made synchronous with the optical phase of the CW laser with approximately 532,361 optical cycles between pulses, which provides the "clock ticks" that are coherently connected to the Hg+ transition.
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