This New Record in Laser Beam Stability Could Help Answer Physics' Biggest Questions

Scientists are trying to create a global network of atomic clocks that will allow us to better understand the fundamental laws of physics, investigate dark matter, and navigate across Earth and space more precisely.

To be effective, these clocks will need to be linked together quickly through layers of the atmosphere, which is not easy. A laser beam has been kept stable across a distance of two kilometers.

The new link is 100 times more stable than anything that's been put together before. It shows that the stability is around 1,000 times better than the atomic clocks these lasers could be used to monitor.

The results show that the phase and amplitude stabilization technologies presented in this paper can provide the basis for ultra-precise timescale comparison of optical atomic clocks through the turbulent atmosphere.

Scientists developed a laser link capable of holding its own through the atmosphere last year, and the system builds on that.

Researchers shot a laser beam from a fifth-floor window to a reflector 1.2 kilometers away. For a period of five minutes, the beam was bounced back to the source.

The team was able to keep the laser stable by using noise reduction techniques, temperature controls, and tiny adjustments to the reflector. The air is calmer and less dense higher in the atmosphere than at ground level, which is likely to equate to ground-to-satellite turbulence.

Laser accuracy has remained fairly constant for a decade or so, but we've seen some significant improvements recently, including a laser setup operated by the Boulder Atomic Clock Optical Network.

The setup used a pulse laser rather than a continuous wave laser. Continuous wave lasers offer better stability and can transfer more data in a set period of time.

David Gozzard from the University of Western Australia says that both systems beat the current best atomic clock.

Einstein's general theory of relativity is one of the tests scientists will be able to perform once an atomic clock network is put together.

Scientists hope to be able to work out where general relativity does and doesn't hold up by comparing the timekeeping of two atomic clocks. The clock should tick faster if Einstein's ideas are correct.

Its usefulness doesn't stop there either. Lasers like this could be used to connect two points in space.

Gozzard says that you can't run fiber optic cable to a satellite.

The research has been published.