Monthly Archives: October 2014

Generally speaking

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My high-school calculus teacher had a mustache like a walrus’s and shoulders like a rower’s. At 8:05 AM, he would demand my class’s questions about our homework. Students would yawn, and someone’s hand would drift into the air.

“I have a general question,” the hand’s owner would begin.

“Only private questions from you,” my teacher would snap. “You’ll be a general someday, but you’re not a colonel, or even a captain, yet.”

Then his eyes would twinkle; his voice would soften; and, after the student asked the question, his answer would epitomize why I’ve chosen a life in which I use calculus more often than laundry detergent.

http://www.sell-buy-machines.com/2013/02/why-prefer-second-hand-equipment-over-new.html

Many times though I witnessed the “general” trap, I fell into it once. Little wonder: I relish generalization as other people relish hiking or painting or Michelin-worthy relish. When inferring general principles from examples, I abstract away details as though they’re tomato stains. My veneration of generalization led me to quantum information (QI) theory. One abstract theory can model many physical systems: electrons, superconductors, ion traps, etc.

Little wonder that generalizing a QI model swallowed my summer.

QI has shed light on statistical mechanics and thermodynamics, which describe energy, information, and efficiency. Models called resource theories describe small systems’ energies, information, and efficiencies. Resource theories help us calculate a quantum system’s value—what you can and can’t create from a quantum system—if you can manipulate systems in only certain ways.

Suppose you can perform only operations that preserve energy. According to the Second Law of Thermodynamics, systems evolve toward equilibrium. Equilibrium amounts roughly to stasis: Averages of properties like energy remain constant.

Out-of-equilibrium systems have value because you can suck energy from them to power laundry machines. How much energy can you draw, on average, from a system in a constant-temperature environment? Technically: How much “work” can you draw? We denote this average work by < W >. According to thermodynamics, < W > equals the change ∆F in the system’s Helmholtz free energy. The Helmholtz free energy is a thermodynamic property similar to the energy stored in a coiled spring.

http://www.telegraph.co.uk/property/propertyadvice/jeffhowell/8013593/Home-improvements-Slime-does-come-out-in-the-wash.html

One reason to study thermodynamics?

Suppose you want to calculate more than the average extractable work. How much work will you probably extract during some particular trial? Though statistical physics offers no answer, resource theories do. One answer derived from resource theories resembles ∆F mathematically but involves one-shot information theory, which I’ve discussed elsewhere.

If you average this one-shot extractable work, you recover < W > = ∆F. “Helmholtz” resource theories recapitulate statistical-physics results while offering new insights about single trials.

Helmholtz resource theories sit atop a silver-tasseled pillow in my heart. Why not, I thought, spread the joy to the rest of statistical physics? Why not generalize thermodynamic resource theories?

The average work <W > extractable equals ∆F if heat can leak into your system. If heat and particles can leak, <W > equals the change in your system’s grand potential. The grand potential, like the Helmholtz free energy, is a free energy that resembles the energy in a coiled spring. The grand potential characterizes Bose-Einstein condensates, low-energy quantum systems that may have applications to metrology and quantum computation. If your system responds to a magnetic field, or has mass and occupies a gravitational field, or has other properties, <W > equals the change in another free energy.

A collaborator and I designed resource theories that describe heat-and-particle exchanges. In our paper “Beyond heat baths: Generalized resource theories for small-scale thermodynamics,” we propose that different thermodynamic resource theories correspond to different interactions, environments, and free energies. I detailed the proposal in “Beyond heat baths II: Framework for generalized thermodynamic resource theories.”

“II” generalizes enough to satisfy my craving for patterns and universals. “II” generalizes enough to merit a hand-slap of a pun from my calculus teacher. We can test abstract theories only by applying them to specific systems. If thermodynamic resource theories describe situations as diverse as heat-and-particle exchanges, magnetic fields, and polymers, some specific system should shed light on resource theories’ accuracy.

If you find such a system, let me know. Much as generalization pleases aesthetically, the detergent is in the details.

Apply to join IQIM!

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Editor’s Note: Dr. Chandni Usha is an IQIM postdoctoral scholar working with Prof. Eisenstein. We asked her to describe her experience as an IQIM fellow.

Just another day at work!

Just another day at work!

When I look back at how I ended up here, I find myself in a couple of metastable states. Every state pushed me to newer avenues of knowledge. Interestingly, growing up I never really knew what it was like to be a scientist. I had not watched any of those sci-fi movies or related TV series as a kid. No outreach program ever reached me in my years of schooling! My first career choice was to be a lawyer. But a casual comment by a friend that lawyers are ‘liars’ was strong enough to change my mind. Strangely enough, now the quest is for the truth, in a lab down at the sub-basement of one of the world’s best research institutes.

I did my masters in Physics at this beautiful place called the Indian Institute of Science in Bangalore. I realized that I like doing things with my hands. Fixing broken instruments seemed fun. Every new data point on a plot amused me. It was more than obvious that experimental physics is where my heart was and hence I went on to do a Ph.D. in condensed matter physics. When I decided to apply for postdoctoral positions, an old friend of mine, Debaleena Nandi, told me to look up the IQIM website. That was in November 2012, and I applied for the IQIM postdoctoral fellowship. My stars were probably aligned to be here. Coincidentally, Jim Eisenstein, my adviser, was in India on a sabbatical and I happened to hear him give a talk. It left such a strong impression in my mind that I was willing to give up on a trip to Europe for an interview the next day had he offered me a position. We spoke about possible problems, but no offer was in sight and hence I did travel to Europe with my mind already at Caltech. IQIM saved me from my dilemma when they offered me the fellowship a few days later.

Now, why choose IQIM! Reason number one was Jim. And reason number two was this blog which brought in this feeling that there exists a community here; where experimentalists and theorists could share their ideas and grow together in a symbiotic manner. My first project was with an earlier postdoc, Erik Henriksen, who is now a faculty at Washington University in St. Louis. It was based on a proposal by fellow IQIM professor Jason Alicea which involved decorating a film of graphene with a certain heavy metal adatom. Jason’s prediction was that if you choose the right adatom, it could endow some of its unique properties such as strong spin-orbit coupling to the underlying graphene sheet. One can thus engineer graphene to what is called a topological insulator where only the edges of the graphene sheet conduct. Erik had taken on this task and I tagged along. Working in a very small campus with a close-knit community helps bounce your ideas around others and that’s how this experiment came into being. I found it particularly interesting that Jason and his colleagues often ask us, the experimentalists, whether some of the ideas they have are actually feasible to be performed in a lab!

The IQIM fellowship allows you to work on a variety of fields that come under the common theme of quantum information and matter. In addition to providing an independent funding and research grant, the fellowship offers the flexibility to work with any mentor and even multiple mentors, especially in the theory group. In experimental groups however, that flexibility is limited but not impossible. The fellowship gives you a lot of freedom and encourages collaborations. IQIM theory folks have a very strong and friendly group with a lot of collaborations, to the extent that it is often hard to distinguish the faculty from the postdocs and students.

Apart from a yearly retreat to a beautiful resort in Lake Arrowhead, the social life at IQIM is further enhanced through the Friday seminars where you get to hear about the work from postdocs and graduate students from IQIM, as well as other universities. IQIM’s outreach activities have been outstanding. A quick look at this blog will take you from the PhD Comics animations, to teaching kids quantum mechanics through Miinecraft, to hosting middle school students at the InnoWorks academy and a host of other activities. This note will not be complete without mentioning about our repeated efforts to attract women candidates. My husband lives in India, and I live right across the globe, all for the love of science. I am not alone in this respect as we have two more women postdocs at IQIM who have similar stories to tell. So, if you are a woman and wish to pursue a quality research program, this is the place to be, for together we can bring change.

Now that I have convinced you that IQIM is something not to be missed, kindly spread the word. And if you are looking for an awesome opportunity to work at Caltech, get your CV and research statement and apply for the fellowships before Dec 5, 2014!

Science at Burning Man: Say What?

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Burning Man… what a controversial topic these days. The annual festival received quite a bit of media attention this year, with a particular emphasis on how the ‘tech elite’ do burning man. Now that we are no longer in the early September Black Rock City news deluge I wanted to forever out myself as a raging hippie and describe why I keep going back to the festival: for the science of course!

This is a view of my camp, the Phage, as viewed from the main street in Black Rock City.

This is a view of my camp, the Phage, as viewed from the main street in Black Rock City. I have no idea why the CH-47 is doing a flyover… everything else is completely standard for Burning Man. Notice the 3 million Volt Tesla coil which my roommates built.

I suspect that at this point, this motivation may seem counter-intuitive or even implausible, but let me elaborate. First, we should start with a question: what is Burning Man? Answer: this question is impossible to answer. The difficulty of answering this question is why I’m writing this post. Most people oversimplify and describe the event as a ‘bunch of hippies doing drugs in the desert’ or as ‘a music festival with a dash of art’ or as ‘my favorite time of the year’ and on and on. There are nuggets of truth in all of these answers but none of them convey the diversity of the event. With upwards of 65,000 people gathered for a week, my friends and I like to describe it as a “choose your own adventure” sort of experience. I choose science.

My goal for this post is to give you a sense of the sciency activities which take place in my camp. Coupling this with the fact that science is a tiny subset of the Burning Man ethos, you should come away convinced that there’s much more to the festival than just ‘a bunch of hippies doing drugs in the desert and listening to music.’

I camp with The Phage, as in bacteriophage, the incredibly abundant virus which afflicts bacteria. There are about 200 people in our camp, most of whom are scientists, with a median age of over 30. Only about 100 people camp with the Phage in any given year. The camp also houses some hackers, entrepreneurs and artists but scientific passion is unequivocally our unifying trait. Some of the things we assembled this year include:

3 million Volt musical Tesla coil at night and during assembly

Dr. F and Dr. B’s 3 million Volt musical Tesla coil. Humans were inserted for scale.

Musical Tesla coil: two of my roommates built a 3 million Volt musical Tesla coil. Think about this… it’s insane. The project started while they were writing their Caltech PhD theses (EE and Applied Physics) and in my opinion, the Tesla coil’s scale is a testament to the power of procrastination! Thankfully, they both finished their PhDs. After doing so, they spent the months between their defenses and Burning Man building the coil in earnest. Not only was the coil massive–with the entire structure standing well over 20 feet tall–but it was connected through MIDI to a keyboard. Sound is just pressure waves moving through air, and lightning moves lots of air, so this was one of the loudest platforms on the playa. I manned the coil one evening and one professional musician told me it was “by far the coolest instrument he has ever played.” Take a brief break from reading this and watch this video!

Dr. Brainlove

Dr. Brainlove getting ready for a midnight stroll and then getting a brainlift.

Dr. Brainlove: we built a colossal climbable “art car” in the shape of a brain which was covered in LEDs and controlled from a wireless EEG device. Our previous art car (Dr. Strangelove) died at the 2013 festival, so last winter our community rallied and ‘brainstormed’ the theme for this vehicle. After settling on a neuroscience theme, one of my campmates in Berkeley scanned her brain and sent a CAD file to Arcology Now in Austin, TX who created an anatomically correct steel frame. We procured a yellow school bus which had been converted to bio diesel. We raised over $30k (there were donations beyond indiegogo.) About 20 of my campmates volunteered their weekends to work at the Nimby in Oakland: hacking apart the bus, building additional structures, covering the bus with LEDs, installing a sound system, etc. One of the finishing touches was that one of my campmates who is a neurosurgeon at UCSD procured some wireless EEG devices and then he and some friends wrote software to control Dr. Brainlove’s LEDs–thus displaying someone’s live brain activity on a 30′ long by 20′ tall climbable musical art car for the entire playa to see! We already have plans to increase the LED density and therefore put on a more impressive interactive neural light show next year.

Sugarcubes: in 2013, some campmates built an epic LED sculpture dubbed “the sugarcubes”. Just watch this video and you’ll be blown away. The cubes weren’t close to operational when they arrived so there was 48 hours of hacking madness by Dan Kaminsky, Alexander Green and many brilliant others before our “Tuesday night” party. The ethos is similar to the Caltech undergrad’s party culture–the fun is in the building–don’t tell my friends but I slept through the actual party.

Ask a scientist on the left. Science class on the right. Science everywhere!

Ask a scientist on the left (I’m in there somewhere and so is one of my current roommates– another Caltech PhD ’13.) Science class on the right. Science everywhere!

Ask a scientist: there’s no question that this is my favorite on playa activity. This photo doesn’t do the act justice. Imagine a rotating cast of 7-8 phagelings braving dust storms and donning lab coats all FOR SCIENCE! The diversity of questions is incredible and I always learn a tremendous amount (evidenced by losing my voice three years running.) For example, this year, a senior executive at Autodesk approached and asked me a trick question related to the Sun’s magnetic field. Fear not–I was prepared! This has happened before.. and he was wearing a “space” t-shirt so my guard was up. A nuclear physicist from UCLA asked me to explain Bell test experiments (and he didn’t even know my background.) Someone asked how swamp coolers work? To be honest, I didn’t have a clear answer off the top of my head so I called over one of my friends (who was one of the earliest pioneers of optogenetics) and he nailed it immediately. Not having a clear answer to this question was particularly embarrassing because I’ve spent most of the past year thinking about something akin to quantum thermodynamics… if you can call black hole physics and holographic entanglement that.

Make/hack sessions: I didn’t participate in any of these this year but some of my campmates teach soldering/microscopy/LED programming/etc classes straight out of our camp. See photo above.

EEG and LED hacking.

Science talks: we had 4-5 science talks in a carpeted 40ft geodesic dome every evening. This is pretty self explanatory and by this point in my post, the Phage may have enough credibility that you’d believe the caliber is exceptional.

Impromptu conversations: this is another indescribable aspect. I’ll risk undermining the beauty of these conversations by using a cheap word: the ‘networking’ at Burning Man is unrivaled. I don’t mean in the for-dollar-profit sense, I mean in the intellectual and social sense. For example, one of my campmates’ brother is a string theory postdoc at Stanford. He came by our camp one evening, we were introduced, and then we met up again in the default world when I visited Stanford the following week. Burning Man is the type of place where you’ll start talking about MPEG/EFF/optogenetics/companyX/etc and then someone will say: “you know that the inventor/spokesperson/pioneer/founder/etc is at the next table over right?”

Yup, Burning Man is just a bunch of hippies doing drugs in the desert. You shouldn’t come. You definitely wouldn’t enjoy it. No fun is had and no ideas are shared. Or in other words, Burning Man: where exceptionally capable people prepare themselves for the zombie apocalypse.

Check out my friend Peretz Partensky’s Flickr feed if you want to see more photos (and credit goes to him for the photos in this post.)

Making sci-fi teleportation sound less crazy

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Laser beam bending due to a change in the speed of light in water.

If you ever wanted to see a sci-fi plot that expertly applied advanced physical concepts so that with a bit of imagination teleporting a human was not as unbelievable as most of the teleportation scenarios we see in the movies, keep reading.

Years ago, when I was still in Russia, I was working on a back-story for a sci-fi game I was playing with friends. In the game, players were given stones (from Mars!) that could change the fundamental constants of nature: electron charge e, speed of light c and Planck constant h. I had already worked out the effects these stones would produce on the space around them (I suggest it as an exercise to the nerdy reader – once you are done thinking about it, see my answer below), so my next task was to envision a big scientific project centered around those stones, with a solid foundation on real physics and a portal to Mars as a final goal. As it turned out, some unforeseen consequences included blowing up the whole lab and scattering the stones in the nearby forest. That’s the back-story.

It all worked beautifully on paper. I imagined that materials could be programmed to obey different values of fundamental constants. These Martian stones were supposed to be the first encounter humanity had with matter where such effects could be observed and studied. The effects extended to a region around the stone, with weird things happening on the boundary of that region. For one thing, energy was not conserved in the vicinity of these stones.

Now having control over e, c and h, the scientists would leverage this new-found power to try to move the fine structure constant e^2/(\hbar c) to what is known as the Landau pole. Such a feat would result in infinitely strong interactions between particles, so that the energetic content of space-time would jump through the roof and a black hole would form. If one was lucky, even a traversable wormhole would form, which is what the scientists were hoping for, because back on Mars these things could have formed naturally, and the lab wormhole would connect to the Martian network.

If you’ve read all this and are asking yourself “What just happened?”, see all the physical concepts explained below: Continue reading →

The dance of the electrons

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On the day I returned to the lab, Marcus Teague, a post-doc leader in the Yeh Group, was orienting two summer undergraduate interns. As he asked the students questions regarding superconductors and scanning tunneling microscopes (STM) I was happy with the amount of information I readily recalled from previous years. It was a good sign that I was ready to build on the content and skills I had already mastered. This may be expected of a graduate student at Caltech, but I am not a graduate student at Caltech. I am a High School physics teacher.

One of the first tasks assigned to me this summer, as I returned for my third year as an IQIM research intern, was to build and solder a connecting cord for the cryocooler in which we stored superconductors. That’s right – I have been working on cutting edge research involving high temperature superconductivity. But back to the soldering. This cord would communicate information, such as temperature and voltage, from the sensor. It had been years since my undergraduate soldering days at UCLA, but it turned out I was not so rusty. I was able to solder the tiny connecting pieces and show the undergraduate research students how to solder.

This summer I made additional tips for STM. Again, we chemically etched the tips using a Calcium Chloride solution in order to reach an ideal thickness of 1 atom across. We also employed the physical stretch and clip approach to make tips. Each person in the lab has their own philosophy on the best method to make tips. It’s amusing and interesting to compare the different techniques for attempting to make sharp, symmetric tips. Whether chemical or physical, the process to make sharp tips is tedious and time consuming, but imperative for a scan with good resolution.

I also worked with Kyle Chen again for certain projects, one of which involved making a low pass filter which would cut out signals above 2 GHz. We wrapped copper wire around a skewer in order to make a tiny solenoid. Care was taken to ensure the number of loops in one direction was matched in the other to avoid creating a net magnetic field. My first attempt was pathetic, but with each trial and error, I was able to construct decent solenoids. The completed solenoids were soldered to a SMA connector (like the one used for coaxial cable) which became one end of the RF filter. In order to connect the copper tube and SMA electrically, a silver epoxy is used. The solenoids were slid carefully into a small copper tube and then filled with the epoxy, a mixture of copper powder and Stycast A and B at a ratio of 100:28. Silver apoxy needs high temperature baking, above 100 degrees Celsius, in order to set, so the system was then baked in order to solidify our new low pass filter to be placed alongside the sample for STM testing.

This summer we also continued testing the YBCO superconducting samples I helped to make two summers ago with Professor Feng. After etching, the procedure to load the sample into the long, cylindrical, central tube required detailed planning. As with last year, the hood was flushed with Argon gas and then vacuum pumped in order to reduce contaminants. Using gloves in the hood, the sample is daintily set into place. Lifting the giant cylinder with the sample took four of us: two for lifting, one for holding it from the base within the hood and one person adjusting the gas levels.

Next we took the cylinder with the sample downstairs to the subbasement to be vacuum pumped and baked in order to expel all gaseous particles. Finally the central tube was loaded into the STM central chamber and the cooling process began, first with liquid nitrogen and then with liquid helium. Finally, it was time to scan the superconducting samples.

Last summer’s scans of the superconductor were in the 500 mV range. However, this summer’s scans are within 150 mV which will lead to much better resolution of the image and possibly valuable enough data to publish.

Each Friday Nai-Chung Yeh has a group meeting with everyone working in the lab. She thoughtfully discusses each persons’ progress, contributions, and questions from the past week. Her genuine curiosity and passion to discuss the best methods for experimentation are inspirational. She is expressive with her hands as she explains a concept, such as how she thinks the polymer doping is affecting the graphene samples. Each week she inevitably goes to the whiteboard and draws a picture of the hypothesized phenomenon observed in the data for that week. She gives insights from her vast wealth of background knowledge and suggests applicable equations, troubleshooting techniques, and information found in the current literature. It is fascinating to watch her warmly lead this group to a deeper understanding of the research topics at hand. I am moved by her work ethic and ability to balance oversight of the graphene projects, topological insulators, superconductors, and possible new solar cell technology. She supervises each sub-projects’ progress while writing papers, traveling the world over to present, as well as secure funding for research.

It is difficult to believe yet another year has passed. Again it is time to return to my classroom to meet my new 150 students, to get them fired up for learning about the exciting world of Physics. I am eager to share my learning experiences from the last three summers at Caltech.