From The University of Western Australia (AU) via Science Alert (AU) : “This New Record in Laser Beam Stability Could Help Answer Physics’ Biggest Questions”

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From The University of Western Australia (AU)


Science Alert (AU)

The laser setup at the University of Western Australia. Credit: D. Gozzard/UWA.

22 JANUARY 2022

Scientists are on a mission to create a global network of atomic clocks that will enable us to, among other things, better understand the fundamental laws of physics, investigate dark matter, and navigate across Earth and space more precisely.

However, to be at their most effective, these clocks will need to be reliably and speedily linked together through layers of the atmosphere, which is far from easy. New research outlines a successful experiment with a laser beam that has been kept stable across a distance of 2.4 kilometers (1.5 miles).

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

“The result shows 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,” write the researchers in their published paper [Physical Review Letters].

The system builds on research carried out last year in which scientists developed a laser link capable of holding its own through the atmosphere with unprecedented stability.

In the new study, researchers shot a laser beam from a fifth-floor window to a reflector 1.2 kilometers (0.74 miles) away. The beam was then bounced back to the source to achieve the total distance for a period of five minutes.

Using noise reduction techniques, temperature controls, and tiny adjustments to the reflector, the team was able to keep the laser stable through the pockets of fluctuating air. The atmospheric turbulence at ground level here is likely to equate to ground-to-satellite turbulence (the air is calmer and less dense higher in the atmosphere) of several hundred kilometers.

While laser accuracy has remained fairly constant for a decade or so, we’ve seen some significant improvements recently, including a laser setup operated by the Boulder Atomic Clock Optical Network (BACON) Collaboration and tested last March [Nature].

That setup involved a pulse laser rather than the continuous wave laser tested in this new study. Both have their advantages in different scenarios, but continuous wave lasers offer better stability and can transfer more data in a set period of time.

“Both systems beat the current best atomic clock, so we’re splitting hairs here, but our ultimate precision is better,” says astrophysicist David Gozzard from the University of Western Australia.

Once an atomic clock network is put together, among the tests scientists will be able to perform is Albert Einstein’s Theory of General Relativity, and how its incompatibility with what we know about quantum physics could be resolved.

By very precisely comparing the time-keeping of two atomic clocks – one on Earth and one in space – scientists are eventually hoping to be able to work out where General Relativity does and doesn’t hold up. If Einstein’s ideas are correct, the clock further away from Earth’s gravity should tick ever-so-slightly faster.

But its usefulness doesn’t stop there. Lasers like this could eventually be used for managing the launching of objects into orbit, for communications between Earth and space, or for connecting two points in space.

“Of course, you can’t run fiber optic cable to a satellite,” says Gozzard.

See the full article here .


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The University of Western Australia is a public research university in the Australian state of Western Australia. The university’s main campus is in Perth, the state capital, with a secondary campus in Albany and various other facilities elsewhere.

UWA was established in 1911 by an act of the Parliament of Western Australia and began teaching students two years later. It is the sixth-oldest university in Australia and was Western Australia’s only university until the establishment of Murdoch University (AU) in 1973. Because of its age and reputation, UWA is classed one of the “sandstone universities”, an informal designation given to the oldest university in each state. The university also belongs to several more formal groupings, including The Group of Eight (AU) and The Matariki Network of Universities. In recent years, UWA has generally been ranked either in the bottom half or just outside the world’s top 100 universities, depending on the system used.

Alumni of UWA include one Prime Minister of Australia (Bob Hawke), five Justices of the High Court of Australia (including one Chief Justice, Robert French, now Chancellor), one Governor of the Reserve Bank (H. C. Coombs), various federal cabinet ministers, and seven of Western Australia’s eight most recent premiers. In 2018 alumnus mathematician Akshay Venkatesh was a recipient of the Fields Medal. As at 2021, the university had produced 106 Rhodes Scholars. Two members of the UWA faculty, Barry Marshall and Robin Warren won Nobel Prizes as a result of research at the university.


The university was established in 1911 following the tabling of proposals by a royal commission in September 1910. The original campus, which received its first students in March 1913, was located on Irwin Street in the centre of Perth, and consisted of several buildings situated between Hay Street and St Georges Terrace. Irwin Street was also known as “Tin Pan Alley” as many buildings featured corrugated iron roofs. These buildings served as the university campus until 1932, when the campus relocated to its present-day site in Crawley.

The founding chancellor, Sir John Winthrop Hackett, died in 1916, and bequeathed property which, after being carefully managed for ten years, yielded £425,000 to the university, a far larger sum than expected. This allowed the construction of the main buildings. Many buildings and landmarks within the university bear his name, including Winthrop Hall and Hackett Hall. In addition, his bequest funded many scholarships, because he did not wish eager students to be deterred from studying because they could not afford to do so.

During UWA’s first decade there was controversy about whether the policy of free education was compatible with high expenditure on professorial chairs and faculties. An “old student” publicised his concern in 1921 that there were 13 faculties serving only 280 students.

A remnant of the original buildings survives to this day in the form of the “Irwin Street Building”, so called after its former location. In the 1930s it was transported to the new campus and served a number of uses till its 1987 restoration, after which it was moved across campus to James Oval. Recently, the building has served as the Senate meeting room and is currently in use as a cricket pavilion and office of the university archives. The building has been heritage-listed by both the National Trust and the Australian Heritage Council.

The university introduced the Doctorate of Philosophy degree in 1946 and made its first award in October 1950 to Warwick Bottomley for his research of the chemistry of native plants in Western Australia.