Posted in | Quantum Physics

A New Strategy for Modeling Quantum Friction

Princeton University’s theoretical chemists have initiated a technique for modeling quantum friction, or how the environment of a particle drags on it, an annoying problem in quantum mechanics ever since the start of the field. This research has been reported in the Journal of Physical Chemistry Letters.

It was truly a most challenging research project in terms of technical details and the need to draw upon new ideas.

Denys Bondar, Research Scholar, Rabitz Lab

Even at the lowest scale, quantum friction will work, but its effects can be witnessed in routine life. For example, when light excites the fluorescent molecules, it is due to quantum friction that the atoms return back to rest, emitting photons that are visible as fluorescence. Credibly modeling this occurrence has mystified scientists for a century and has received more consideration recently due to its applicability to quantum computing.

The reason why this problem couldn't be solved is that everyone was looking at it through a certain lens.

Denys Bondar, Research Scholar, Rabitz Lab

Earlier models tried to explain quantum friction by taking into account the quantum system as networking with a neighboring, larger system. This bigger system leads to an unmanageable amount of calculations, and to simplify the equations to the relevant interactions numerous approximations were introduced by scientists.

These approximations gave rise to various other models that could only fulfill one or two of the major requirements. Either a valuable observation about the system could be produced, or the Heisenberg Uncertainty Principle could be obeyed, which states that there is an essential limit to the accuracy by which the position and momentum of a particle could be measured at the same time. Even the famous physicist Werner Heisenberg's effort in deriving an equation for quantum friction had mismatched with his uncertainty principle.

The new method, termed Operational Dynamic Modeling (ODM), was presented in 2012 by the Rabitz group. This resulted in the first model for quantum friction to fulfill both demands.

To succeed with the problem, we had to literally rethink the physics involved, not merely mathematically but conceptually.

Denys Bondar, Research Scholar, Rabitz Lab

Bondar and his associates concentrated on the two critical requirements for this model -- that it should follow the Heisenberg principle and create real findings -- and worked back to front to produce the correct model.

"Rather than starting with approximations, Denys and the team built in the proper physics in the beginning," said Herschel Rabitz, the Charles Phelps Smyth '16 *17 Professor of Chemistry and co-author on the work "The model is built on physical and mathematical truisms that must hold. This distinct approach creates a new rigorous and practical formulation for quantum friction," he said.

The research team comprised of research scholar Renan Cabrera and a Ph.D. candidate Andre Campos along with Shaul Mukamel, Professor of Chemistry at the University of California, Irvine.

Their model opens a way towards understanding not merely quantum friction, but also other dissipative phenomena. The researchers intend to discover the methods to change these forces to their benefit. Other theorists are quickly adopting the new prototype of operational dynamic modeling, Rabitz said.

Recalling how they came up with such an innovative approach, Bondar recollected the exclusive conditions under which he initially started exploring this problem. Once he received the proposal to work in Princeton, Bondar waited four months for a US work visa (Bondar is a Ukraine citizen) and thinking about questions related to fundamental physics. During this course of time, he first thought of this approach.

The idea was born out of bureaucracy, but it seems to be holding up.

Denys Bondar, Research Scholar, Rabitz Lab

Source: http://www.princeton.edu

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