Let’s use qubits to look for dark matter.

Examining Akash Dixit’s qubit-coupled cavity in the Schuster Laboratory (http://schusterlab.uchicago.edu/). Photo credit: Reidar Hahn (http://vms.fnal.gov/asset/detail?recid=1955845)

We’re starting a new research program and I’m excited to tell you about it!

Let’s start with the big picture, and then we’ll use subsequent posts to zoom in on the details. The big picture goes like this:

  1. 95% of the mass-energy in the universe is a huge mystery. Everything we see around us — pizza, dinosaur bones, galactic clusters — is made of atoms. But as best we can tell, atoms account for only 5% of the mass-energy in the observable universe. The rest is a big mystery that we call dark matter and dark energy. It would be fair to say that physicists are very interested in sorting out the remaining 95%. Aren’t you? If your everyday senses only reveal 5% of the known universe, what are you missing out on?
  2. Dark matter is very probably made of particles, and we think a great candidate is a particle called the axion. The axion is cool because it solves other problems in physics in addition to dark matter. (We’ll talk about it later, but you can skip ahead and look up the “strong CP problem” if you want.) You may not have heard of axions yet, but the scrabble game on my telephone sure has.
  3. Axions are hard to detect. They’re a bit like neutrinos, in that they’re (probably) all around us but they hardly ever interact with normal matter. You detect them by converting them into photons and then looking for the photons. (Physicists are pretty good at counting photons; we’ve had a century of practice at it.) To further complicate matters, our theorists have narrowed down the axion mass to a window that spans three orders of magnitude. We have to design an axion search that is sensitive to potential masses (or equivalently, photon energies) between meV and μeV.
  4. So: a metaphor. Imagine you’re driving down a desert highway in an old car and you want to listen to the radio. Since you’re way out in the middle of nowhere, the radio is mostly static. How do you find a station? You’d probably tune the radio dial a little bit, listen for a while to see if you could pick out any signal in the noise, tune the dial, listen, tune, and so on. Eventually, if you started to pick out some faint music in the static, you’d know you were getting close. Same for us! In fact, our colleagues have an experiment called the Dark Matter Radio. The key point here is distinguishing signal from noise.

    By Riberto Frederico [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

  5. Reduce, reduce, reduce the noise that competes with the signal. If you give me $100M for a 30-tesla magnet, I can give you a real strong, healthy axion signal. If you don’t have that kind of magnet money laying around, I’ll have to figure out some way to keep noise out of my experiment. One way to do this is to use quantum bits. I’ll get into this in a later post, but the technology we borrow from quantum information science gives us the ability to suppress experimental noise by four orders of magnitude. Not bad!

    An qubit.

So there you go: the broad strokes for finding dark matter using quantum bits. Slowly but surely, we’ll take all those individual menu items above and expand on them in future posts. Exciting times!

Gratitude for Larry Phillips

Larry Phillips is one of the most interesting people I have ever met. I consider him a role model, and I learned today that we lost him to cancer. He was my PhD advisor.

Larry was and is well-regarded in the field of particle accelerator technology. I worked with him on problems related to thin-film superconductivity for accelerating cavities, but he was one of those smart, versatile people who ends up getting involved in all sorts of fun problems. You’ll find that he’s made contributions to the design of cryomodules, RF windows, electropolishing of niobium accelerator components, plasma surface treatments, … it’s a long list. He also had an encyclopedic knowledge of how to actually get things built. He “played against type” that way; he could keep up with condensed matter theorists, metallurgists, machinists, and grad students. In recent years he had gotten involved in the design of accelerator-driven nuclear reactors, and novel methods for detecting dark matter.

This diversity of interests and competence is maybe not surprising if you know anything about his life. Larry lived in New York in the 60s, partying with bohemians and working as a motorcycle courier. He blew glass professionally; he got his PhD working with Hans Meissner (son of Walther Meissner, who discovered the eponymous Meissner effect); he lived on a sailboat for a while; he not only designed his own house, but the construction methods used to build it; he was a devoted husband and father; and he was an excellent mentor for young physicists.

This is the part of the essay where I talk about gratitude. Larry took me on as a student at a time when I was feeling very unsure about myself, academically. I couldn’t have been luckier, in retrospect. He was always available when I needed support, and he also seemed to know when I needed to be left alone to sort things out for myself.

He went out of his way to make opportunities for me. There were the kinds of things you’d expect from a PhD advisor, like professional networking or experimental support. But he also made sure I didn’t graduate without learning how to weld, braze, run the hydraulic press, and how to talk to a machinist. (You’d be surprised how many scientists are not good at this.) And he set an example for me and all the people in our group with his positive attitude. He was always getting enthusiastic for new projects, and declaring that they would be fun. (He would also declare that new projects would be “easy”, but we all knew that when he said “easy” he meant “probably not impossible”.) I had a great time with him.

If you have never been a graduate student, you might not see this last statement as an appropriately big deal. Some of my grad school pals had advisors who worked them like dogs, or completely ignored them, or (in a few terrible cases) were outright emotionally abusive. This sort of thing is unfortunately not uncommon. And while I could never claim that the process of graduating wasn’t stressful, I came out of it feeling like a “real” scientist, with an appreciation for the state of my field and the ways I might contribute to it. I came out feeling positive and ready to go.

That’s why I’m talking about gratitude right now. It’s hard to overstate the enormity of the gift that Larry gave me. And not just me. We threw a surprise party for his 80th birthday just a few months ago, and the crowd there was full of people who will tell you the same things I’ve been telling you now.

Thanks, Larry, from all of us.

Gender bias in STEM fields helps maintain the “gender gap”.

We’ve got an accelerator conference coming up soon. I volunteered to help prepare material addressing issues faced by women in STEM (science, technology, engineering, and mathematics) fields. The title says it all, really.

I suspect that every scientist would benefit from doing this sort of service work now and again. I read some very interesting papers and I learned a ton.

Problems of bias can seem nebulous and impossible to describe, let alone to solve. Something I particularly appreciated about my experience making this poster: the problems are clear and often quantitatively described. What’s more, there are data-driven, concrete solutions to these problems! Assuming your department has the political will to implement these solutions, you can help fix things. Not bad!


New job, new post!

hoorayI took a few months off of blogging so I could focus all my energies on worrying about job applications. And I guess all that worrying paid off because I got a job! I work at Fermilab now, doing basically the same stuff as before.

I want to tell you all about it! But not all at once, because (a) I respect you and your limited free time too much for that; and (b) oh man, Anaïs and I still have so much unpacking to do.

I’m very happy to be blogging at you again. Hello!

Friday Physics Photos: ???



Ok you guys, I’m doing that thing where as I write my next post, I discover that I have more and more things I want to talk about and the post gets longer and longer … Right now it’s an unreadable mess. While you wait for me to carve that mess up into several smaller messes, here’s a little bit of fun.

On my bike ride into work, I passed by another department’s lab. In their parking lot was this totally inexplicable vignette. I have absolutely no idea what’s going on here and I love it. Somebody write me a short story about this.

Sunrise on Haleakalā

Wedding photos: You want to see them, I want to see them, everybody wants to see them!  But oh my goodness, there are so many.  There are about 1,250 photos for us to sort through.

Sorting through our wedding photos may take a little time.

While you’re waiting, I’ll periodically post some photos from the honeymoon.  We went to Maui, because … well, because Maui.  It was totally and completely Maui.  One of the Mauiest things to do on Maui is to sit on top of a volcano at sunrise.  So we did that.  Here are some photos!

This is a crater near the summit of a probably-dormant volcano called Haleakalā, which apparently means “House of the Sun”. (Can you guess why?) The environment is so austere and lunar that the Apollo astronauts came here to train in the 1960s.

Once the sun was up, you could see all the things. All of them.

3,055 meters is apparently not enough elevation for me.

Coming up next: DIY wedding photo booth stories!

LBNL Open House

It is my pleasure to show you low-quality cell phone photos of an impossibly great physics thing.  This is a Lego scale model of the ATLAS experiment, one of the two detectors at CERN responsible for the recent discovery of the Higgs boson.

Here’s what it looks like in real life:

ATLAS Experiment © 2012 CERN

The Lego version is still pretty cool though, right?

A lot of my posts lately have been about particle accelerators and how impressive they are.  (A quick summary: particle accelerators are impressive.)  But I’ve only briefly touched on what you might want to use one for.  Let’s totally talk about that it more detail, very soon.  For now, I’ll just say that discovering fundamental properties of matter at the smallest scales requires some very very impressive, complicated machinery.  Something like 3000 people work on ATLAS.  Some of them develop hardware and maintain the various bits of the detector.  Some of them work on piping the vast amounts of collected data from the detector complex to their computing farm.  And some of them study that data, looking for evidence of new and interesting physics.  Three thousand people!  And this is only one of six detectors operating at CERN right now!

The model is color-coded, by the way. Here’s the key.

The model is built to scale. Look at those little Lego guys! Yes, the detector really is that big.

This wonderful monument of dorkitude was on display at my lab’s recent open house.  I ran a demonstration about the superconducting magnets used in certain kinds of particle accelerators, including the LHC.  I would be very happy to write a post about this, but first I need to get a few more photos together.

PS.  Should we talk specifically about the Higgs boson?  Or did you get enough of that from every other blog in the entire world?  I think it would be interesting to address your questions, if you have any.  (“What is the Higgs” is a fine sort of question to ask.)  I encourage you to post your questions in the comments section.

Transit of Venus

Lots of hard work and travel have kept me away from the blog.  But!  There’s now a huge body of cool stuff to talk about.  New posts will be coming fast and furiously in the following weeks!

Let’s talk real quickly about the transit of Venus.  Aside from being a fascinating, once-in-a-lifetime celestial event, it’s a huge plot point in one of my favorite books of all time, Thomas Pynchon’s Mason & Dixon.  So … read that book?

Anaïs and I went down to the Chabot Space & Science Center to watch the transit.  Not only do they have three enormous telescopes, but the place was lousy with amateur astronomers who brought their impressive gear and were so generous as to share it with us, the great unwashed.

In the center of that photo, towards the bottom, you’ll see a suuuuuper-fancy telescope.  (I don’t care to speculate on how much it cost.)  It’s outfitted with a hydrogen-alpha filter, a narrow-band filter that blocks out most of the light coming from the sun.  It makes possible some insanely detailed images of the solar surface.  Of course, I failed entirely to get any photos of that caliber.

Something even more interesting, though, were the pinhole viewers.  I submit to you that a fancy, multi-thousand-dollar telescope rig is impressive and intimidating to the point that it turns your brain off.  Viz:

Q:  How does this complicated, expensive machine work?

A:  Technology!

Bogus.  Unsatisfying.  Worse, that dialogue is intimidating and can scare people off of asking further questions.  Of course, a sufficiently interested person (sometimes reductively called a “geek”) will bother to pick through the layers of complication until they understand how an arbitrarily complicated machine works.  This is totally great, and it can be very entertaining to watch it happen.  But I think we ought be making more geeks.  As many as possible!

So for those times, like the transit of Venus, when the public comes out in droves to do sciency things, I prefer the following gizmo:

Very simple: filter, lens, mirror, screen.  Anybody can look at this gizmo and figure out how it works.  And, because it’s so simple, the sun’s image moves fast across the page.  You end up with not just an intellectual understanding of the sun’s motion, but a visceral feeling of it as well.  People waited in line for a long time to look through the fancy telescopes, but it seemed to me that they stayed longer at the pinhole viewers and asked more questions.

I hope you got a chance to see the transit!  I hope you had lots of fun seeing it!

Particle Accelerator Q&A

Just real quick:  If you’re curious about accelerators and you also do the twitters, you may want to check out this (I’m told this is an actual word that people use)  tweetup: #LabChat.  It’s a twitter Q&A with some US Department of Energy scientists.  Here’s a link for more information:


I know Gigi Ciovati, one of the participating scientists.  He’s a sharp cookie, and pleasant to talk with besides.