Quantum dance

When they are cooled to a temperature close to absolute zero, the atoms of the material behave like waves, losing their individual identity - and adopting a group identity

Dr. Ehud Altman. struggle
Toms cooled to a temperature close to absolute zero do not "freeze in place", as one might intuitively think. Instead, they obey the laws of quantum theory, and continue to dance a delicate, but precise, quantum dance. Advanced technologies developed in the last decade allow scientists to confine a group of atoms and cool them down to a temperature lower than that prevailing at the edge of the universe - a billionth of a degree above absolute zero. Under these conditions, the material organizes itself in a special state of aggregation, called, after the predictors of its existence, "Bose-Einstein condensation". Dr. Ehud Altman from the Department of Condensed Matter Physics at the Weizmann Institute of Science, Prof. Eugene Demler from Harvard University in the USA, and Prof. Anatoly Pulkovnikov from Boston University in the USA, developed a unique approach that allows using the results of experiments with cooled atoms as a kind of "microscope" that allows Watch the quantum dance of the atoms. These observations allow, among other things, to identify new aggregation states of the material.
The atoms of the material in the state of Bose-Einstein condensation do not interact with each other. At the low temperature where they are found, they lose their "particle" properties, and behave as waves. As the temperature drops, the waves of the different atoms become more and more overlapping, until at a certain point they lose their individual "identity" in favor of a "group identity" shared by all the atoms in the aggregate. Thus, instead of many waves, one big common wave is created.
When two such groups, locked in separate traps, are allowed to spread out and make contact with each other, they wrestle in a pattern reminiscent of the wrestle of two ripples spreading in water as a result of, for example, throwing a stone, or falling a drop of water. This interference is a direct proof of the wave nature of the particles. Such a state of condensed matter, where the waves "dance" in a coordinated manner, is considered a particularly ordered state of the matter (or, in the language of physicists: "the phenomenon of the cooperative wave is static, or without oscillation"). This is a stable result that repeats itself from experiment to experiment.
But, under other conditions, for example when the movement of the particles is limited to a single line or plane, collisions between the particles of matter become inevitable. As a result, waves of different particles become entangled with each other, and the coordinated and harmonious dance is disrupted by quantum fluctuations, and becomes irregular. In an article recently published in the scientific journal "Records of the National Academy of Sciences of the USA" (PNAS), Dr. Altman and his research partners showed that observations of the interference patterns can teach about the quantum fluctuations of the atoms.
The interference pattern created by such disturbed condensations is irregular, and includes distortions and twists that vary from experiment to experiment. These changes are, in fact, the traces of the quantum oscillation.
Dr. Altman and his research partners were able to calculate the statistical properties of the deformations, and showed that they directly express the quantum activity of the material particles. French scientists, who recently applied this theory and observed a system of cooled atoms moving on a plane, were able, for the first time in this type of system, to notice the transition of the atoms from one state of aggregation to another state of aggregation.
In another article, published in the scientific journal Nature Physics, Dr. Altman and his research partners describe, in more detail, the statistical distribution of the random fluctuations in the interference pattern. It turns out that this distribution is similar to the distribution of fluctuations that describes rare and powerful phenomena such as earthquakes or the collapse of the stock market. These findings may help in the development of a technology that will allow the measurement of very small changes in the gravitational field, by identifying the degree of compatibility (or incompatibility) between waves originating from Bose-Einstein condensations. Additional applications may be technological systems for efficient mapping of geological layers for the purpose of oil detection, or for the detection of gravity waves. 
 
 
Changes in the aggregation modes

The change in the state of aggregation, that is, in the organization of the structure of the material, is sometimes a consequence of temperature changes, which is a measure of the random fluctuations of the atoms that make up the material. For example, when water is cooled, the water particles slow down their movement until the water changes its state of aggregation and becomes ice. But further cooling, to a temperature close to absolute zero, will not bring the particles to a complete stop. In this situation, changes in the aggregation states are not caused by temperature changes, but by the quantum fluctuations. These fluctuations arise from the principle of uncertainty, according to which it is impossible to know at the same time both the position of a particle and its speed. The mysterious nature of the quantum fluctuations allows matter to organize itself into new and unfamiliar states of aggregation.
The quantum behavior of single particles is well known today, but how do the principles of quantum theory affect the behavior of many particles that together form the matter in the "world of large objects"? Many scientists, in different parts of the world, including the Weizmann Institute of Science, are focusing on the effort to find an answer to this basic question.

In the picture: two clusters of cold atoms (the dark squares in the center) are released from confinement, and spread into overlapping clouds (light ellipses). The common cloud is lit from one side and casts its shadow on the screen. The pattern of stripes that is obtained is the result of the interference between the clouds. From the statistical characteristics of the bands it is possible to learn about the nature of the quantum fluctuations that took place within the clusters of atoms before the expansion