The Center for Controlled Quantum Systems is an interdisciplinary unit within PEP that links together the research activities of six of the faculty (Search, Martini, Yu, Strauf, Horing, and Malinovskaya) through a single unifying theme of controlling physical systems that are governed by quantum mechanics. The activities broadly fall under the subfield of physics known as atomic, molecular, and optical physics and focus on using light to directly control and manipulate the quantum mechanical properties of atoms, molecules, semiconductors as well as other more exotic materials such as Bose-Einstein condensates and graphene.
Quantum mechanics represents one of the greatest intellectual achievements in all of science both for its incredible mathematical elegance and unparalleled accuracy in explaining the behavior of systems ranging from sub-atomic particles to atoms and molecules all the way up to macroscopic systems such as superconductors and lasers, which represent the two most commercially successful ‘quantum technologies’. The central idea of quantum physics is that matter behaves both like a wave and a particle. In order to observe the wave properties of matter, the waves must be coherent in the same way that light or water waves must be coherent in order to interfere or diffract. Macroscopic quantum phenomena such as lasers and superconductors are the exception and not the rule. In general, the ever-present noise in the environment destroys this very delicate coherence of matter waves in our everyday world, which explains why we do not directly observe quantum phenomena. At the microscopic level, the quantum wave nature of matter is by contrast responsible for all of the physical properties.
Since the beginning of the twentieth century, technology has been driven by a quest towards the ever smaller. Vacuum tubes that filled an entire hand have been replaced with transistors only a few nanometers across. ‘Nanotechnology’, which was first envisaged by the Nobel prize winning physicist Richard Feynman fifty years ago, has become the latest trend for research in engineering and the physical sciences. Quantum control is nanotechnology pushed to the limit. While nanodevices such as carbon nanotubes, graphene, and semiconductor quantum wells and quantum dots all have physical properties determined by quantum physics, the dynamics of such devices are typically manipulated in a manner that destroys the quantum coherence. However by preparing and manipulating such systems in a manner that carefully preserves the matter wave coherence, an entirely new domain of phenomena can be achieved that hold the potential to radically alter technology as we know it.
Over the last few decades experimental physicists have learned how to use lasers to manipulate micro and mesoscopic systems in a way that preserves the coherence of the quantum mechanical matter waves while at the same time eliminating environmental noise by various newly discovered techniques such as laser cooling down to temperatures of only a few nano-Kelvin. (The Nobel prize in physics was awarded for this work in 1997, 2001, and 2005.) The laboratory technology and our theoretical understanding have now reached a ‘tipping point’ where this basic science is mature enough to make the crossover to technology. One example is the ability to produce an atomic superfluid known as a Bose-Einstein condensate first created in 1995 (Nobel prize 2001), which used to require years of effort and a laboratory full of equipment. One can now purchase prefabricated equipment for a few thousand dollars allowing almost anyone to make such a condensate on a corner of their desk (www.coldquanta.com).
The number of technological applications of quantum control pursued by experimental and theoretical physicists around the world has dramatically increased over the last decade. A few examples of the more important applications for communications, computing, military, healthcare, and homeland security include:
- Quantum Cryptography
- Quantum Computing
- CARS based bioimaging
- Matter interferometers and gyroscopes
- Quantum sensing and quantum metrology
- Quantum imaging and quantum lithography
A more complete survey can be found in the 2007 report of the National Research Council “Controlling the Quantum World: The Science of Atoms, Molecules, Photons”, www.nap.edu/catalog.php.
Core members of the CCQS are:
Dr. Norman Horing
Dr. Svetlana Malinovskaya
Dr. Rainer Martini
Dr. Chris P. Search
Dr. Stefan Strauf
Dr. Ting Yu