Friday, January 11, 2013

Linking A Particle's Mass To Time

This is rather surprising and unique.

A paper to be published in Science claims to have made a clock that measures time by linking it to a mass.

Abstract: Historically, time measurements have been based on oscillation frequencies in systems of particles, from the motion of celestial bodies to atomic transitions. Relativity and quantum mechanics show that even a single particle of mass m determines a Compton frequency ω0 = mc2/ ħ, where c is the speed of light and ħ is the reduced Planck constant. A clock referenced to ω0 would enable high-precision mass measurements and a fundamental definition of the second. We demonstrate such a clock using an optical frequency comb to self-reference a Ramsey-Bordé atom interferometer and synchronize an oscillator at a subharmonic of ω0. This directly demonstrates the connection between time and mass. It allows measurement of microscopic masses with 4 × 10−9 accuracy in the proposed revision to SI units. Together with the Avogadro project, it yields calibrated kilograms. 

That's definitely an astounding accomplishment if this is verified. They actually could somehow get at the frequency associated with a particular mass.

A news report on this work can be found here, which reveals a bit more of the issue surrounding this measurement.

The idea for the clock stemmed from the quantum principle that particles also behave as waves, and vice versa. In particular, Müller and his colleagues wanted to determine how frequently the wave form of a single atom oscillates, a quantity that in quantum mechanics is inherently linked to the atom’s mass. Then the researchers could use those oscillations like swings of a pendulum to create a clock.

The snag in Müller’s plan was that it’s impossible to directly measure the oscillation frequency of waves of matter. The frequency of these waves is about 1025 hertz, 10 orders of magnitude higher than that of visible light waves. So Müller and his colleagues came up with an apparatus that creates two sets of waves — one based on a cesium atom at rest and another on the atom in motion. The researchers measured the frequency difference between the waves and then used that number, a manageable 100,000 hertz or so, to calculate the much larger oscillation frequency of cesium at rest.
Let's see this will work out.



cb said...

This is wonderful physics, thank you to report it ! As a teacher in high school my hidden agenda is to make the Planck postulate and its formula as popular as the Einstein one among students and now there is this great experiment exemplifying matter waves, Compton frequency and relativistic time dilation !
Apropos mass-frequency quantum-relativistic equivalence I can't resist quoting the following fascinating anagram in French, composed recently by Etienne Klein a physicist and Jacques Perry-Salkow a pianist : "le boson scalaire de Higgs = l'horloge des anges ici-bas"
(literal translation : the Higgs scalar boson / angels' clock on earth)... not exactly an anagram in English unfortunately

cb said...

Pentimento (repentir)

Since my last comment I have started to read more and thought deeper about this nice experiment and I have also learned about former experiments and claims by the same group (*). It seems to me now that interpreting the last results in terms of genune "Compton" frequency measurements is doubtful to say the least...
Anyway I was very pleased today to listen to a senior student asking me about this experiment after reading a blog post from le Monde (!

(*) I personally recommend reading and