Squeezed light and a bunch of experimental physicists

OzGrav team
The OzGrav team at the University of Western Australia. Photo: Ju Li

Squeezed light and a bunch of experimental physicists

Being a physics educator at the University of Western Australia (UWA) is a bit different than being one at the University of Oslo. Of course, there is the change of scenery: Instead of overlooking the Oslo fjord, I now get to ponder the stretches of Swan River. The academic difference, though, is even more profound.

While we have our own small section for physics education at UiO, the physics education group at UWA is part of the OzGrav education and public outreach program. OzGrav is the Australian Research Council Centre of Excellence for Gravitational Wave Discovery. The project is impressive, hosting more than 130 members across six Australian affiliations with 19 international collaborating organizations.

It goes without saying that OzGrav pursues exceptional research and scientific discoveries. This vibrant academic environment translates to work days that offer plenty of intellectual stimulation. There are student lunch meetings, weekly talks, workshops, outreach activites, and generally the huzzle and buzzle of a bunch of researchers all trying to push the boundaries of our understanding of the Universe. It's fantastic!

Swan River in Perth
The University of Western Australia overlooks Swan River. Photo: Magdalena Kersting

A fun change

The one thing that I find particularly enjoyable is the fact that I am now mostly surrounded by experimental physicists. Seeing that I’m a mathematical physicist by training, I haven’t put my hands on experiments and equipment since my undergraduate years. In fact, most of my colleagues over the years have either been theoretical physicists or mathematicians – or lately, educators and social scientists. It’s a fun change to hear about ill-adjusted mirrors or to discuss how to squeeze light just the right way to make the measurement work.

And squeezing light is what physicists literally do to refine and improve gravitational wave detectors. The other day I joined a group meeting in which Jue Zhang, one of our PhD students, talked about quantum noise reduction. Gravitational wave detectors need to be super sensitive: They have to be able to detect length differences far smaller than a single proton. It’s crazy what experimental physicists these days can do, right? But instead of just being awestruck, I tried to understand precision measurements of gravitational wave detectors a bit better.

Constantly bubbling particles and antiparticles

It turns out that the sensitivity of gravitational wave detectors is limited by vacuum fluctuations. Vacuum fluctuations are an intrinsic feature of our universe. Instead of being empty, the vacuum is constantly bubbling with particles and antiparticles that come into existence and are immeditaley destroyed again.

While theoretical physicists are intrigued by these little symphonies of particle creation and annihilation, experimentalists are more likely to think of these fluctuations as noise: Noise that keeps measurements from being precise. For many decades, physicists struggled to overcome the quantum measurement barrier due to this noise that would disturb measurements in the detectors.

Squeezed light discussion
Members of the OzGrav team discuss how to squeeze light. Photo: Magdalena Kersting 

The barrier is related to Heisenberg’s famous uncertainty principle that puts a limit on the sensitivity of measurements. You cannot avoid the uncertainty principle – but you can bypass it in a nifty way by squeezing light on the quantum level. Squeezed light will indeed have noise below the vacuum level – allowing extremely precise measurements.

It is a wonderful technology that combines quantum physics and relativity to measure the strongest energy outbursts in the universe on the smallest scales imaginable.

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