From the Einstein-Bohr debate to a new quantum revolution

Professor Alain Aspect (source: Wikimedia)
Professor Alain Aspect (source: Wikimedia)

Institutional Communication Service

8 October 2016

What is matter really made of? Are physics and particles fully understood? Towards the end of the 19th century, the laws of classical physics seemed to explain in a comprehensive way the nature of the atom and its elements. Then, in the early 1900s, scientists began to understand how the issue were much more complex, laying the basis for what would become the first quantum revolution. Today, however, though we have access to a technology capable of operating at near-atomic size, even those theoretical models are starting to falter, as they seem unable to explain every phenomena which we are now able to observe: it is perhaps time, like 100 years ago, for a new “quantum explanation”. 

On Friday, October 7th, 2016, USI and the International Balzan Prize Foundation hosted at the Lugano campus Professor Alain Aspect, the acclaimed French physicist regarded as one of the leading experts of quantum correlation between particles. During his public lecture (in English), Aspect explained what lies behind this paradigm, presenting the evolution of the scientific debate on the subject and involving the different views from leading physicists such as Podolsky, Rosen, Einstein, Schröder, Bohr, Bell and Aspect himself. The French physicist’s experiments on the “entanglement” of photons in fact are – according to a number of observers – opening the door to a second and new quantum revolution that could entail technological spillovers unthinkable until now. “Only time can tell us whether a certain scientific discovery can be considered a ‘revolution’, whether it will have been fundamental for science and for humanity”, said Prof. Aspect. “I would prefer using the term ‘evolution’ to describe fundamental scientific discoveries, as these always happen in sequence, with a discovery that leads to another one, and so on.” 

With concerns to the second quantum revolution, it is important to understand what happened with the ‘first revolution’, in the early decades of the 20th Century”, Prof. Aspect added. “At that time it was discovered how electrons would behave like “waves” when forced to stay in tight spaces, like around the nucleus of the atom. This wave-like movement (the so-called wave-particle duality, which American physicist Richard Feynman called the ‘great mystery’ of quantum mechanics) was important for scientists to understand the stability of atoms, why they would not ‘fall’ on the nucleus despite their negative polarity – this was understood only after the emergence of quantum physics. These discoveries allowed for fantastic and fundamental inventions, such as the transistor and the laser.

 “The second quantum revolution initiated in the 1970s,” continued Aspect, “when physicists started isolating, observing and even controlling single microscopic quantum objects, such as electrons. Before then, during the first quantum revolution, scientists had to resort to probabilistic and statistical methods. About the famous entanglement, this was actually a theory developed by Albert Einstein in 1935, by which two particles that find themselves in a quantum state behave like a single entity, leading to believe that there is some sort of ‘influence’ that travels faster than the speed of light. This results from the description of a related, or ‘entangled’, pair, which takes place in an abstract, mathematical space – a space where everything happens in a ‘normal’ way. However, physicists need to work also in an ordinary environment, in laboratories. In 1982, I managed to demonstrate experimentally the so-called Principle of Locality, which is the space, or the environment, in which it ‘seems’ that the aforementioned influence can actually be faster than light speed. This work is the basis for having earned the Balzan Award in 2013”, concluded Alain Aspect.


Professor Aspect was awarded the Balzan Award in 2013 “For his pioneering experiments which led to a striking confirmation of Quantum Mechanics as opposed to local hidden-variable theories. His work has opened the way to the experimental control of entangled quantum states, the essential element of Quantum Information Processing.”

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