The Center for Quantum Control at Stevens Institute of Technology
November 10, 2008
With the different backgrounds of its five faculty members, the Stevens Center for Quantum Control has all the knowledge for developing a new quantum device right in its own building. Since the Center’s inception in 2004, the separate pieces of the research puzzle are starting to come together. “We expect a big leap forward this year,” according to one of the researchers.
“The key to any new scientific discovery is control,” said Rainer Martini, assistant professor of Physics. “And the new development in physics will come from control of quantum particles, such as photons and electrons.” Martini is one of five faculty members in the Center for Quantum Control, located in the Burchard Building in the Division of Physics and Engineering Physics. Together with Ting Yu, Svetlana Malinovskaya, Stefan Strauf and Christopher Search, he designs devices based on new quantum systems.
According to Martini, the Center is booming. “We now have some 25 postdocs and PhD-students. The different expertise of all the faculty members attracts physicist from different backgrounds, making the center more heterogeneous. Moreover, the center collaborates with universities worldwide, such as Princeton, CUNY, UCLA, the University of Belgrade in Serbia, Fordham University, and the University of Heidelberg in Germany. Companies such as MagiQ in Manhattan are also involved.”
“Quantum control was a real buzz word when we started the Center in 2004,” said co-founder and assistant professor Christopher Search. “The purpose of the Center’s research is to engineer the quantum world, and manipulate nature at the quantum level.”
According to Search, having this central theme instead of a specific research topic unites the researchers. “Some of the research is in the world of optics, while other is in solid state physics,” said Search. “The Center will stand the test of time; quantum control will still be important in fifty years, although the topics may be different.”
“We try to go all the way from a theoretical calculation to incorporating the device in a new camera or laser,” Rainer Martini added. Martini designed a new near-infrared laser which can broadcast at mid-infrared frequencies. “With this laser you can see through fog, because the photons don’t scatter as much because of their frequency. Last year, we tested the laser beam by broadcasting the beam to a skyscraper across the harbor, in Manhattan.” The laser beam has inspired the Stevens spin-off PredatorVision, which develops a new type of security camera that can see through smoke and fog.
The laser can transmit data at 100 GB per second. “Electrically we cannot transmit data that fast, but the laser pulse modifies the energy that the molecules in the air absorb, so we get no disturbance. This will help the transmission of data on long distances, maybe even from here to Texas.”
Another application of this laser is optical detection of plastics, for instance in airport security.
“With this finding, we have put a new knob on the laser, as if your PC can also open the garage door,” said Martini.
Another possible application of this laser is to enhance Raman radiation. In Raman detection, molecules absorb photons. The absorption pattern tells you which molecule it is. However: you measure the energy that gets away, so you have an indirect measurement. Martini: “With this laser, we could enhance the radiation that gets away and make the detection more sensitive, or maybe look at this radiation with a second beam and measure a single molecule.”
While Martini works on the application in Raman optimization, Svetlana Malinovskaya, associate professor of Physics, takes care of the more fundamental aspects of this project. “We aim to manipulate a femtosecond laser pulse to affect predetermined properties of molecules,” Malinovskaya explained. “For example: With modulated laser pulses, one could break the specific bond in a molecule to initiate a chemical reaction, or to selectively excite a molecular vibration of known frequency and receive the Raman signal from it.” Malinovskaya investigates how to modulate the pulse properties and how to use pulse sequences to achieve a desired quantum yield.
The key application of pulse manipulation lies in imaging of biological samples. Malinovskaya explained: “If one would like to get an image of a molecular specific structure constituted of only unsaturated fats, one could program the laser pulses to excite only the double bond in these compounds.” The key word in this field is a phenomenon called coherence. “All molecules interact with the environment. For example, they collide with water molecules in the solution. By doing this, they lose their energy and their quantum properties, such as coherence.” In a recent publication in Optics Letters, Malinovskaya describes her discovery that she can program the laser to give fast pulse trains, which restore coherence periodically. Together with faculty member Ting Yu, Malinovskaya studies applications in quantum computing and quantum information processing where coherence control is currently one of most challenging issues.
With his background in atom and quantum optics, Christopher Search’s research is more on the fundamental side. One of his research topics is quantum pumping, where he distorts the wave function of an electron to generate a current, instead of using a voltage, which is the case with normal circuits. “A big advantage of quantum pumping is that the electron movement acquired by quantum pumping is so slow that you don’t generate heat. In modern computers, heat generation is a significant barrier to making electronic devices smaller; you always need to cool your circuits.”
Together with Stefan Strauf, Search is studying the electron Sagnac interferometer. This device is a million times smaller than the bulky optical gyroscopes that planes and missiles currently use to determine their position. Search: “We would like to build an electron interferometer made out of graphene, a form of carbon, and use it to detect rotational motion. Although I hope most applications are in civilian navigation technology, this device would also be useful to militaries around the world. Our goal is not necessarily to produce a device that will be on the market in a few years, but rather to sow the scientific seeds for the new technologies that will change the world in the long term.”
Search is also planning new projects for the future; he recently received an NSF grant to look for ways to control the production of molecules. “If you point a light beam on two ultra cold colliding atoms, they will form a molecule by absorbing a photon,” Search explained. “We are analyzing this process in an optical cavity, where light bounces back and forth between two mirrors. If you manipulate the laser in that cavity, you can control how many molecules are produced and how fast.”
Other scientists have only been able to store individual pairs of atoms in a lattice of intersecting laser light and to control molecule formation since 2005, so Search’s work is at the cutting edge. Search: “We are making a first step in controlling chemical processes on the quantum level.”
Search is also involved in investigating spintronics. This technology uses the spin of electrons for data storage and processing and could yield dramatically smaller computer circuits that operate at the level of individual electrons. This area has already had important technological successes, namely the Gigabyte hard drives used in everyone’s iPod. The discoverers of that phenomenon received the Nobel Prize in Physics in 2007. Search: “We look at the behavior of quantum dots in optical cavities. Quantum dots are artificial atoms that are grown in semiconductors. We are studying these dots for use as spin current batteries and switches that can be used to generate and control currents of pure spin in microchips. Currently there doesn’t exist any practical device similar to an ordinary battery for the creation of spin currents.”
The Center also organizes the Seminar Series on Control of Quantum Systems where speakers from outside Stevens give guest lectures on the topic. The talks were presented by internationally recognized leaders in Quantum Control that include Prof. Moshe Shapiro from the University of British Columbia, Prof. Herschel Rabitz from Princeton University, and Prof. Chris Monroe from the University of Maryland. This initiative broadens the opportunities for the exchange with the scientific achievements, and development of the scientific collaboration within topical research areas. Besides, the seminars are meant to give graduate students a broad overview of the field and to get more students involved.
If students are interested in fundamental learning about the theory and application of advanced methods of control of ultrafast dynamics in atoms and molecules, they can take the graduate course ‘Methods of Quantum Control’ developed and taught by Malinovskaya.
Because the five faculty members all have their own expertise, the center’s research on quantum control comprises several levels, from theoretical calculations on a certain device (Ting Yu) to the actual application (Rainer Martini). “We have the whole development spine in-house,” said Martini. “This is a strong point of our center.”
The completeness of the center also fits well into Stevens Institute of Technology, which aims to combine fundamental scientific research with applications for business. “Stevens takes not only academic publications into account, but also spin-offs and patent applications,” said Martini.
This year, the faculty members are ready to start working together, now that they have their own separate labs up and running. All faculty members have proven themselves individually in their fields of expertise. Martini said, “And now we are ready for a jump. When we all get in the same room and discuss new options for devices, there is so much creativity. We have ideas for three new grant applications already. I expect major breakthroughs this year.”
By Mariëtte Bliekendaal-van Dorp
Special to the Stevens News Service