Nist: New Optical Clock More Accurate Than Cesium

LordPhatal writes "NIST researchers have demonstrated a new kind of atomic clock that has the potential to be up to 1,000 times more accurate than today's best clock. The new clock is based on an energy transition in a single trapped mercury ion.

Comments

And in a year, they'll be using alcohol instead.

[tunah]

Duh! When this clock breaks the mercury will go everywhere! They already went through this phase with thermometers.

Hmm....

[rtaylor]

I've always wondered just how they determine how reliable a clock is.

Afterall, can't measure meters without a meterstick. Do they simply take a N Cesium clocks and average out their time to determine how close a single Mercury based clock sticks to it? Or did I miss the memo where we could acurrately time trillionths of a second?

Re:Hmm....

[norton_I]

Basically, the accuracy of a reference clock in principle determined by making two identical clocks, starting them synchronized, and measuring how long before they drift by an average of 1 second.

This has to do with how cold your atomic fountain is, and how well you isolate the particular magnetic sublevel you define the second in terms of.

Now, if you want to move to a mercury standard clock, you can do two things: first, calculate with QED the ratio of the freqencies between the transitions in cesium and mecury of interest. I don't know if we can do this well enough for these purposes or not. Second, you can redefine the second in terms of the oscillation frequency of some mercury transition at least within the accuracy of a current cesium clock.

The important thing to note is that mand physicists don't really care about how long a second is, as much as they care that two clocks run at the same rate, even if it is wrong.

Re:And in a year, they'll be using alcohol instead

[Anonymous Coward]

well, ONE single ion can only go SOMEwhere, not EVERYwhere, unless they know its momentum very precisely.

Re:Go down and take a tour!

[Gopher]

Unfortunately, tours are suspended due to security concerns. :( It's too bad, really, becuase I agree that the tour is really cool.

However, you can take an online tour if that floats your boat.

Re:um

[esonik]

The above wording is imprecise. 9,192,631,770 Hz is the frequency of the electromagnetic wave that triggers a certain transition in a cesium-133 atom. So, what oscillates is not the complete atom, but the electric and magnetic field. Details can be found here

How do they count the ticks?

[mmontour]

One advantage of the new clock is that it ticks much faster. Today?s international time and frequency standards, such as NIST-F1, measure an atomic resonance of about 9 billion cycles per second. By contrast, the new NIST device monitors an optical frequency more than 100,000 times higher or about 1 quadrillion (US) cycles per second.

A 9 GHz oscillation can be hooked up directly to electronic circuits, counters, PLLs, etc. My first question when I read this article was, how the heck do you synchronize anything else to a "frequency" that's in the optical / ultraviolet range? I found some more information on this page and this one, so I guess that's how this new clock works.

Re:um

[CentrX]

Originally, the second was defined to be 1/86,400 of the mean solar day. Because this is inaccurate due to irregularities in the Earth's rotation, that is the length of the second would change, finer standards were chosen. These finer standards are based on the original standard, but because they are defined in another way, they will not change unless the fundamental properties of the universe do.