Meet a CQTian: Loh Huanqian

Huanqian joined CQT after completing her PhD with Nobel prize-winner Eric Cornell - and she says physics was once her worst school subject!
18 April 2014

Loh Huanqian joined CQT in December 2013 having completed a PhD with Nobel prize-winner Eric Cornell – and she says physics used to be her worst subject! The picture she's holding is from her experiment with Dzmitry Matsukevich. It shows individual trapped ions.

Who are you?

I'm Huanqian, a Research Fellow, and I am working in the group of Dzmitry Matsukevich. I'm from Singapore.

How did you end up a scientist?

I got into physics research in Junior College, when I was 16 or 17. I did an attachment at Nanyang Technological University and a six week stint at MIT. When I was at MIT I thought, oh, I like this place, and after that I decided to take an A*STAR scholarship to study physics there. At MIT I tried a bunch of research internships. I liked the one involving lasers and atoms the best, and I ended up doing a stint at CQT after my undergrad – actually, I was here before it became CQT. Then I went off to do my PhD.

You did your PhD in the states, too?

Yes, at the University of Colorado with Eric Cornell. The project was precision spectroscopy on molecular ions, with the goal of measuring how round the electron is.

Why would we care how round the electron is?

There's this theory that describes very much of physics, known as the standard model. We know it to be incomplete. Since it doesn't explain why there's so much matter compared to antimatter, it doesn't explain why we are both sitting here. There are other models that go beyond the standard model to explain this 'charge-parity violation'. The same theories that allow for larger charge-parity violation also allow for the fact that the electron is egg-shaped instead of round. [Eric Cornell gave a colloquium at CQT on this research: watch the video here].

Is what you're doing at CQT related?

It's not trying to measure how round the electron is, but we're also doing precision spectroscopy on molecular ions. We're probably going for the ultimate goal of measuring whether there is a change in fundamental constants, such as the ratio of the electron mass to the proton mass. These constants, usually you learn in the textbook at school that, well, they're just constants that you write down and they should be such and such a number. But there is reason to believe that these constants have changed over time as the universe evolves, and so it would be interesting to find out if they are changing.

And the fact that you can do things very precisely, that allows you to measure a very small change over a short time?

Or, rather, we can compare our value against what astronomers have measured already. Astronomers look at stars and collect various spectra of what is in the stars, which tells them the constants from a while back. We are trying to figure out what these constants are now.

How long does it take to measure a constant?

Usually precision spectroscopy can go for as long as you need to chase after the next digit. For me, working with molecular ions is cool not just for the big goal but in itself. There are very few groups working with molecular ions around the world. It is not easy to gain quantum control over a system that not only has the same degrees of freedom as an atom, but that can also rotate and vibrate.

In practice, in the lab, what are you doing?

The experiment is mostly built up but it's still quite dynamic. Sometimes there are things like lasers we want to realign or make more stable, to make sure things don't drift during a measurement. It's a combination of electronics, doing laser jobs, and knowing some vacuum techniques as well. Then when everything is running smoothly, you press a button, and you see the data come in. Of course, you have to do some coding to make sure that when you press the button the equipment does what it's supposed to do! Then you have to think about what the data means.

What's something that you enjoy about research?

I like thinking about problems. When I was in secondary school, when I first started learning physics, it was actually my worst subject. I think I had to go for remedial class. I remember my very first exam was on optics and I failed it! Don't let Dzmitry hear that! But I liked it because I didn't understand it, and I spent a lot of time thinking about it. That's how it became better.

As you've earned two degrees since, Dzmitry shouldn't worry! So it's thinking about problems that motivates you?

Yes, I still like thinking about problems. It feels satisfying when you solve a problem and you understand what's going on. In research we don't always understand what's going on, but that's what gets you hooked.