Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum analog of Ulam's conjecture can guide molecules, reactions

09.08.2007
Like navigating spacecraft through the solar system by means of gravity and small propulsive bursts, researchers can guide atoms, molecules and chemical reactions by utilizing the forces that bind nuclei and electrons into molecules (analogous to gravity) and by using light for propulsion. But, knowing the minimal amount of light required, and how that amount changes with the complexity of the molecule, has been a problem.

Now, by creating a quantum mechanical analog of Ulam’s conjecture, researchers at the University of Illinois and the University of California have expanded the flexibility and controllability of quantum mechanical systems.

“Using photons, we can harness chaotic motion to control chemical reactions and to move quantum objects, such as nanoclusters, molecules and buckyballs,” said Martin Gruebele, a William H. and Janet Lycan Professor of Chemistry, and the director of the Center for Biophysics and Computational Biology at Illinois.

Gruebele and co-author Peter Wolynes, a professor of chemistry and biochemistry at the University of California, describe their work in a paper accepted for publication in Physical Review Letters and posted on the journal’s Web site.

Given sufficient time, classical chaotic motion will spontaneously connect two points in phase space with arbitrary precision. In 1956, American mathematician Stanislaw Ulam conjectured that owing to this phase space-filling aspect of chaotic trajectories, a minimal series of energy expenditures would suffice to transfer a body from one point to another much more rapidly than by spontaneous motion.

Ulam’s conjecture is now routinely used to steer spacecraft around the solar system with minimal energy expenditure.

“The idea is that a complex system like our solar system has lots of planets, moons, and asteroids that can fling spacecraft gravitationally anywhere you want,” said Gruebele, who is also a professor of physics and biophysics, and a researcher at the Beckman Institute. “Rather than powering a rocket on a brute force, direct route, you can shoot your spacecraft near some moon, and let the moon do most of the work.”

Using photons as an energy source, electrons within molecules can move in much the same way as spacecraft in the solar system. But, there is a hitch: Quantum mechanics, not Newtonian dynamics, must be used to describe the motions. In quantum mechanics, the system is described by a wave function, or quantum state.

In their quantum mechanical analog of Ulam’s conjecture, Gruebele and Wolynes show there are limits on how efficiently an external force can nudge a system from a given initial state to a target state. They use the concept of a “state space” to describe all the possible quantum states of the system.

“We can calculate where this initial state will most likely go, and we can calculate where the target state will most likely come from,” Gruebele said. “We can then identify places in state space where the two are closest to one another.”

Those locations are where energy is most efficiently applied to perform the desired quantum transformation from initial state to target state. The researchers’ equations also tell them how many photons are needed, and set fundamental limits on the time required.

“We can wait for the best possible moment to use the least amount of energy,” Gruebele said. “What we have is a fast and accurate method for computing the most efficient way of steering a quantum system between two specified states.”

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht Astronomers release most complete ultraviolet-light survey of nearby galaxies
18.05.2018 | NASA/Goddard Space Flight Center

nachricht A quantum entanglement between two physically separated ultra-cold atomic clouds
17.05.2018 | University of the Basque Country

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>