Excitonics Center

The MIT/Harvard Center for Excitonics has been chosen by the Department of Energy as an Energy Frontier Research Center.

The Research Laboratory of Electronics (RLE) at the Massachusetts Institute of Technology (MIT) will be home to one of 46 new multi-million-dollar Energy Frontier Research Centers (EFRCs) announced today by the White House in conjunction with a speech delivered by President Barack Obama at the annual meeting of the National Academy of Sciences. The EFRCs, which will pursue advanced scientific research on energy, are being established by the U.S. Department of Energy Office of Science at universities, national laboratories, nonprofit organizations, and private firms across the nation.


The new Center for Excitonics will be a comprehensive center on the science and applications of excitons. It will be based in RLE but include researchers throughout MIT, as well as Harvard University and Brookhaven National Laboratory.

Excitons are the crucial intermediate for energy transduction in low cost, disordered semiconductors. The Center’s researchers will tackle the following questions: How are excitons created and destroyed? How can we control the migration of excitons? How do they move through interfaces and around defects? How can we control the transition between coherence and incoherence, or localization and delocalization? And finally, how can we build excitonic devices that address society’s needs for a new generation of energy technologies? Potential technological outcomes from the Center’s activities include the development of efficient synthetic and room-temperature-reconfigurable light absorbing antennas with sub-5-nm feature sizes for solar cells; stable organic light emitting devices exploiting spin orbit coupling to achieve internal fluorescent efficiencies approaching 100%, and novel nanowire, nanowire heterostructure and nanowire-quantum dot aggregate materials for solid state lighting; and thin film, non-tracking solar concentrators with power efficiencies exceeding 30%.

These are very excitonic exciting news for us. We worked very hard in the proposal, and pushing a shadow Excitonic Center, waiting to see if the real center will be approved. The Excitonics Seminar series has been fantastic so far, with the best speakers in the field. We have very high expectations that the breakthroughs that will come out of our center will lead to more efficient solar energy technologies.

I guess somebody up there likes me.
-The Sirens of Titan

SQuInT, APS, Publications

I’m back.

After a long, tough, wintery and busy month, I’m back.

Progress report follows.

Alright, first, I went to SQuInT. The Southwestern Quantum Information and Technology conference isn’t true to its name. It was held in the Northwest, Seattle, where beautiful weather seemed to tunnel through the mountains’ potential just for us. The conference itself was very productive and I had the opportunity to see family, friends and collaborators.

In other news, we submitted a paper on Open Quantum Systems and Time Dependent Current Density Functional Theory titled Time-dependent current-density functional theory for generalized open quantum systems to the journal Physical Chemistry, Chemical Physics (PCCP). It has been accepted for publication and might appear in a special issue on Time Dependent Density Functional Theory.

We also submitted a related paper to another journal, paper titled Time-Dependent Density Functional Theory for Open Quantum Systems using Closed Systems. You can read it in the arXiv.

Finally, I went to the APS March Meeting, where 7,000 physicists took over the city of Pittsburgh, where I was able to find bars decorated with Roberto Clemente posters, where a restaurant served Carrucho (Conch). Sometimes I feel the APS March meeting is too big, too overwhelming, talks are too short, and there is too much going on simultaneously. But then I’m surprised by meeting people I hadn’t seen in almost 10 years now, and by how APS March meeting always lead to new collaborations.

Exciting times these are.

“I have wept three times in my life. Once when my first opera failed. Once again, the first time I heard Paganini play the violin. And once when a truffled turkey fell overboard at a boating picnic.”
-Gioachino Rossini

Cutting down: Postdocs and Investors

As I said before, Harvard lost a lot of money, $8Billions, to be exact. Hiring is frozen everywhere, impacting postdocs whose contracts are year-to-year.  I’m optimistic that the grants we have written will get funded; I like it here, except the horrible weather, and don’t want to leave yet.

Now, Harvard fires the people that managed the endowment.

Harvard University said today that it’s cutting about a quarter of the staff — or about 50 jobs — from the company that manages its endowment after the fund tumbled $8 billion in four months.

The estimated 22 percent decline, by far the largest in higher education, was the sharpest drop in the endowment’s history. The fund was valued June 30 at $36.9 billion before falling to $28.7 billion by October.

The university is projecting the endowment will decline by a total of 30 percent by the end of the fiscal year in June.

DisCover: Quantum rules Photosynthesis (follow up)

The cover of the Discovery issue that discusses the work at my lab.
The cover of the Discover issue that discusses the work at my lab.

This is a follow up to the post about the Discover magazine article that discusses our group’s research studying quantum effects in photosynthesis. The issue (February) is out in stores now. I never liked Discover magazine much, but this time I had to purchase it.

Click here to see the full article.

Quantum mechanics is controlling my thoughts

Kids were very different then.  They didn’t have their
heads filled with all this Cartesian Dualism…
-Monty Python on Nostalgia

Quantum rules Photosynthesis

My main research project was featured in Discover magazine! The cover has some abstract flowery-looking explosion that represents quantum mechanics.

My work in the Aspuru-Guzik group focuses on the quantum aspects of excitonic transfer as applied to photosynthetic complexes and solar harvesting devices. The mistitled article can be found here:

Is quantum mechanics controlling your brain?

Then came the revelation: Instead of haphazardly moving from one connective channel to the next, as might be seen in classical physics, energy traveled in several directions at the same time. The researchers theorized that only when the energy had reached the end of the series of connections could an efficient pathway retroactively be found. At that point, the quantum process collapsed, and the electrons’ energy followed that single, most effective path. […]

Elated by the finding, researchers are looking to mimic nature’s quantum ability to build solar energy collectors that work with near-photosynthetic efficiency. Alán Aspuru-Guzik, an assistant professor of chemistry and chemical biology at Harvard University, heads a team that is researching ways to incorporate the quantum lessons of photosynthesis into organic photovoltaic solar cells. This research is in only the earliest stages, but Aspuru-Guzik believes that Fleming’s work will be applicable in the race to manufacture cheap, efficient solar power cells out of organic molecules.

Unfortunately, the pretty good article about quantum effects in photosynthesis is ruined by its title, title that refers only to the final section of the article containing some wild speculations on quantum mechanics and consciousness. Please, don’t take that last part seriously. Although there is strong experimental evidence supporting the role of quantum effects in photosystems, there isn’t anything that suggests a connection between quantum mechanics and consciousness.

Donate computing time for the environment

There is the environmental need and the political will to take solar energy seriously. Our group at Harvard is leading several theoretical and computational efforts to develop more efficient solar panels. One of our efforts (not my project) is to use computational chemistry tools to find novel materials that would lead to better solar technologies. This is mostly performed by trial and error. A lot of it.

A certain molecular arrangement is “proposed” randomly, and the computer calculates its molecular energy to see if it makes sense (if it is a realistic material) and then if it is useful for solar panels. This trial and error approach takes a long time, requires a lot of computational power, but it can be parallelized in a straight-forward manner.

How can you help us?

By downloading the Harvard Clean Energy Project software. With it, you can donate your unused computer cycles, when the computer is on but not using the processor much, to help perform the combinatorial calculations. With these small computing contributions from thousands of students it is expected that the calculations will be done ten times faster than in a supercomputer.

Right now it is only available for Windows, but in the next few weeks it should be compatible with Linux and Mac too.

The project has had a lot of visibility, the other day BBC called our office!

Check out all the news articles written about it.

No greens for crimson

A few weeks ago, Nobel Laureate Al Gore came to visit our campus to officially inaugurate the new initiative to make Harvard University environmentally friendly. The following banner can now be seen everywhere around the university.

Crimson is a reference to the university colors and sports teams, The Crimsons.

Not too long ago we got an email from the president of the university announcing how, thanks to the economic disaster, things were going to get ugly here. Harvard’s endowment has been managed very conservatively and successfully through its history, making it the richest university, attracting people like me to do do research. About $$frac{1}{3}$$ of the employees here get paid from the profits generated from the investments of this endowment. With the market crash, there is now place to make money, no matter how safe you play it.

Yep, no greens for crimson.

The news hit the main media of how big the losses have been. And they have been big.

Harvard Endowment Fell 22 Percent in Four Months

Harvard’s endowment—the largest in higher education—fell 22 percent in four months from its June 30 value of $36.9 billion, marking the endowment’s largest decline in modern history, University officials announced yesterday.

The precipitous drop will require Harvard’s faculties to take a “hard look at hiring, staffing levels, and compensation,” wrote University President Drew G. Faust and Executive Vice President Edward C. Forst ’82 in a letter informing the deans of Harvard’s losses.

What is the impact that these news will have on my fellowship? I don’t know.

A Stochastic Goodbye to Ito

Kiyoshi Ito, a Stochastic Man of Longevity
Kiyoshi Ito, a Stochastic Man of Longevity

Mathematician Kiyoshi Ito died at the young age of 93 this past month. Ito was the inventor of calculus for stochastic processes, known as the Ito Calculus.

Calculus, as invented by Isaac Newton and Gottfried Leibniz, studied the rate of change of nice smooth variables, $$x$$ in terms of their differentials, infinitesimal quantities described by $$dx$$. To properly define a Leibniz differential, the variable $$x$$ must be nicely behaved. Words that are often associated with nice variables are smooth, differentiable and/or continuous.

This limited the scope of applications of calculus. In particular, it does not apply to a random process. A random process, such as rolling a dice, is not nicely behaved, each roll of the dice being very different from the one before, its values literally jumping around a lot. A processes given by probabilistic, random, rules is called a stochastic processes.

My favorite stochastic process is the random walk, and is defined as follows.

Imagine a drunk guy, who can either take a step forward or backwards. Each direction has an equal probability, so you can think of the drunk guy carrying out a random walk, where the direction of each step is determined by a coin toss, heads giving a step forward while tail signifying a step backwards.

This class of problems are very common in statistical physics, finance and biology. The difficulty with doing calculations of stochastic processes is that the variables are not nice, and thus their differentials are not well defined.

Ito invented his own type of differential for exactly this purpose. Although the rules he computed were inspired by traditional calculus, they are on a different class of their own. It’s impact is so broad that is difficult to think of a field with a component of applied math where Ito calculus does not play a role.

New York Times has the story.

$$langle mbox{Ito} rangle = 46.5 $$

Imagine a molecule. Now Imagine a quantum computer solving it.

A quantum circuit, a molecular spectra, a molecule: will they ever have a threesome?
A quantum circuit, a molecular spectra, a molecule: will they ever have a threesome?

So, we have the periodic table. We know that atoms combine into molecules depending on their energy spectrum, its energy levels. We know quantum physics, the theory that reigns in the atomic regime.We know math. We know quite a lot, actually.

So, we want to create new chemicals. Having new materials would give us new technologies, having new molecules would provide us with new medicines, saving millions of lives.

How come it is so hard to use what we know to get what we want?

The problem is that atoms have many electrons, and you have to calculate the equations for each electron. But, electrons interact with other, the solution of the equations of one depend on the solutions of the equations of the other. The solutions are interconnected, coupled. This is know as the many body problem. This makes solving the equations very hard.

Although we know what to do to calculate the energy of a complicated molecule, we can’t actually do it. It takes too long, even for a computer. Computers get faster every year, but they don’t get fast fast enough for the problem. Making the molecule just a bit more complicated demands us to have a computer much much much more powerful than for one a bit simpler. In other words, the problem of solving the energy of a molecule doesn’t “scale” well.

Enter quantum computers.

Unlike a conventional computer, Aspuru-Guzik and his colleagues say, a quantum computer could complete the steps necessary to simulate a chemical reaction in a time that doesn’t increase exponentially with the reaction’s complexity.

What is a quantum computer? How is it different from other computers? What tricks can it do to solve chemical reactions faster than a normal computer?

This blog is about those questions and more. Stay tuned.