Exotic states of matter

100 years after the Bose-Einstein condensation

When and Where: 14-05-2024 | 17:30 | Sala Paladin, Palazzo Moroni, Via del Municipio 1, Padua

One hundred years ago, on 4 June 1924, a young Indian physicist called Satyendra Nath Bose sent Einstein an article in English on the collective behavior of ‘light quanta’, the photons, offering a new deduction of the results obtained by Planck in 1900 on black body radiation. Bose asked Einstein if the paper seemed noteworthy to him and, if so, if it could be translated into German and published in some prestigious journal, such as the Zeitschrift für Physik. Einstein was not only enthusiastic about the article but translated it himself and sent it to the Zeitschrift für Physik.

In the following months, he deepened Bose’s work by applying it not only to quanta of light but to a gas of atoms. From these contributions came the first quantum statistic, the one now known as the Bose-Einstein statistic, which applies to the collective behavior of bosons, particles characterized by integer values (0, 1, 2 …) of a particular quantum quantity, spin. For the sake of completeness, let us say that the second quantum statistic, that of Fermi-Dirac per particle, known as fermions, with half-integer spin (1/2, 3/2 ..), only appeared in 1926 thanks to the independent contributions of Enrico Fermi and Paul Dirac.

In November 1924, Einstein realized that the gas of atoms he had studied manifested a paradoxical property: ‘From a given temperature, the molecules “condense” without attractive forces, i.e. they aggregate at zero velocity’. In practice, he envisaged a state with indistinguishable particles all occupying the same volume. Experimental proof of the existence of ‘Bose-Einstein condensation’ (BEC) would only come many years later, in 1995, because the temperatures at which BEC occurs are very low indeed, close to absolute zero.

The exotic properties of quantum matter as a consequence of the Bose-Einstein statistic have enabled the understanding of phenomena, e.g. superconductivity, which like BEC are proof that quantum properties manifest themselves not only in the ultra-small, but also in macroscopic or quasi-macroscopic situations at very low temperatures.

Over the last thirty years, with the refinement of techniques for cooling matter, the applications of BEC have become increasingly numerous, ranging from the creation of atomic lasers to atomic clocks, from sensors for measuring gravitational or magnetic forces to quantum computers and telecommunications.

Chiara Fort, from the Department of Physics and Astronomy at the University of Florence, will talk about how Bose-Einstein condensation came about and what its applications were, are and will be at the meeting ‘Conversations on Quantum Mechanics’.  This is the second annual meeting promoted by the Department of Physics and Astronomy (DFA) of the University of Padua as part of the project entitled ‘Quantum Frontiers’.

This project, financed by the Ministry of University and Research through the call for proposals ‘Departmental Projects of Excellence’, aims to enhance the DFA’s expertise in all frontier areas of research in which the quantum nature of matter and radiation plays a fundamental role. These scientific and technological developments are also of undoubted interest outside the scientific community. For this reason, the project envisages a series of dissemination initiatives to enable the general public to grasp the importance of this research, its spin-offs in the technological sphere, and the challenges it poses in the cultural, social and economic spheres.