Endless oscillations: A theoretical study on quantum systems

May 28, 2015, International School of Advanced Studies (SISSA)

A quantum system never relaxes. An isolated system (like a cloud of cold atoms trapped in optical grids) will endlessly oscillate between its different configurations without ever finding peace. In practice, these types of systems are unable to dissipate energy in any form. This is the exact opposite of what happens in classical physics, where the tendency to reach a state of equilibrium is such a fundamental drive that is has been made a fundamental law of physics, i.e., the second law of thermodynamics, which introduces the concept of entropy.

This profound difference is the subject of a study published in Physical Review A, conducted with the collaboration of the International School of Advanced Studies (SISSA) of Trieste and the University of Oxford. Giuseppe Mussardo, professor at SISSA, together with Milosz Panfil, SISSA research fellow, and Fabian Essler from the University of Oxford carried out a theoretical analysis with which they demonstrated the peculiarity of one-dimensional quantum systems, as well as explaining the non-local nature of these systems.

"The main point of our work was not only realizing the dramatic difference between classical and quantum reality," explains Mussardo, "but also discovering the existence of quantum systems that are extremely robust with respect to any external stimulus, thanks to their specific laws of symmetry. These laws, in particular, demand not only the conservation of energy but also of innumerable other quantities, which maintain the same value over time as a result".

Mussardo and colleagues also made another discovery: to be able to predict the evolution of quantum systems and their statistical characteristics, we should think of them as being defined not by every point in space (and therefore continuous) but only by discrete points.

It is as if these systems lived "intrinsically" on a grid, explains Mussardo (who also adds that "this came as a big surprise"), "so that on a large scale we have to take into account non-local effects".

This study, as well as shedding light on some peculiar effects revealed by recent experiments on mixtures of and spin chains, opens up interesting scenarios on the control of extensive quantum systems and their use for future memory architectures and quantum algorithms.

Explore further: Cloud of quantum particles can have several temperatures at once

More information: Generalized Gibbs ensembles for quantum field theories Phys. Rev. A 91, 051602(R) – Published 14 May 2015. dx.doi.org/10.1103/PhysRevA.91.051602

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Macksb
1 / 5 (1) May 29, 2015
This is consistent with a theory of coupled periodic oscillators that I have proposed and applied in many Physorg posts over the last four years. The theory began with Art Winfree circa 1967. It is well developed mathematically. See Steve Strogatz and Ian Stewart, "Coupled Oscillators and Biological Synchronization." Winfree and disciples such as Bard Ermentrout have applied it to biology with great success. "Periodic oscillations" are the stuff to which Winfree's theory applies.

I have borrowed Winfree's theory and applied it to physics, on the ground that Max Planck's quantum of energy is a periodic oscillation, and so all of physics is fundamentally a system of periodic oscillations interacting with each other.

The above article supports my theory in several ways. "Endless oscillations" as a "system." "Defined only by discrete points." "On a large scale we have to take into account non-local effects."

Winfree's theory predicts how such systems self-organize.
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