Mitchell Walker

Graduate Student in Quantum Light and Matter

What do you do?

Originally from Sheffield, I came to Durham in 2017 to study physics. I always wanted to get a PhD (even though my family didn't really have an academic background, so I didn't know exactly what that meant!). Initially, I was interested in astrophysics, but during my undergrad I fell in love with optics and atomic physics. After an experimental Masters' project, I was sold and ended up sticking in Durham for my PhD, which I'm nearly at the end of!

How are you involved in this area of science? 

I work on an atomic clock experiment as part of Quantum Light and Matter (QLM). We use lasers to cool strontium atoms to temperatures more than a million times colder than outer space. We then capture these atoms in traps made out of light - we can even catch a single atom!

We excite an electron in each trapped atom using light with a very specific energy. When our laser has the right energy, we see a response from our atoms: we can use the atoms like a tuning fork to keep our laser "locked" at the right energy. This way, we know the frequency that our laser light is vibrating at, and we can use electronics to count those vibrations and measure time!

Atomic clocks can currently measure 300 million years to within a second - but physicists want to improve this! Our experiments hope to demonstrate new ways to make clocks even more precise.

What do you love about this topic?

Getting to catch, experiment on, and image such a small number of atoms is something that is always amazing to think about! I've always been really fascinated by clocks and time, so getting to work on an experiment so similar to how time is measured around the world, and learning all the ins and outs, is a hugely amazing thing. Most of all, though, I love having conversations with my family and friends about all this stuff - it's really incredible to be able to explain some of the incredible things going on at the quantum level!

How does this work deliver real-world impact?

Being able to precisely measure the time is crucial for GPS, which in the modern world is something we rely on. GPS works by timing how long it takes to send a signal to and from satellites orbiting the planet - so the more precisely you can measure time, the better you can work out where you are in the world!

Precision timekeeping also has huge impacts on research into some of the biggest mysteries in modern physics, from dark matter to gravitational waves! More precise tools for measuring let physicists rule out some answers and narrow in on the truth!