Physicist Claude Cohen-Tannoudji Dies at 93

The field of atomic physics lost one of its leading figures on Thursday when Claude Cohen-Tannoudji died at the age of 93. The French physicist shared the 1997 Nobel Prize in Physics for developing methods to slow and trap atoms using laser light.

The Laboratoire Kastler Brossel, a research institute at the École Normale Supérieure in France, announced the death. The statement confirmed his passing but did not release specific details about the circumstances or his final days.

Cohen-Tannoudji’s work solved a major challenge in studying matter. At room temperature, gas atoms move randomly at speeds around 2,500 mph. Freezing them into solids or liquids makes them too crowded to analyze individually. His team used laser beams to create a substance scientists call optical molasses. This process slows atoms by causing them to absorb and emit photons, which reduces their motion and lowers their temperature.

Starting in 1988, he led experiments at the École Normale Supérieure using helium atoms. In 1995, his team reached a temperature of 0.18 millionths of a degree above absolute zero. At this point, the atoms moved at less than an inch per second. He shared the Nobel Prize that year with Steven Chu and William Daniel Phillips for these advancements in laser cooling.

Born in Constantine, Algeria, in 1933, Cohen-Tannoudji came from a Jewish family that had fled persecution in Europe and North Africa. He entered the École Normale Supérieure in Paris in 1953. Initially interested in mathematics, he switched to physics after attending lectures by Alfred Kastler, a 1966 Nobel laureate. Cohen-Tannoudji completed his doctorate in 1962 and later joined the faculty at the Collège de France in 1973.

At the Collège de France, he established a laboratory in 1984 to study laser cooling. He hired Alain Aspect, who would win the 2022 Nobel Prize for work on quantum entanglement. The group developed a technique known as Sisyphus cooling, which allowed them to repeatedly trap and cool atoms. Cohen-Tannoudji wrote more than six books, including two on quantum physics still used in French universities. He received the Legion of Honor and dozens of honorary degrees.

In a 2004 interview, he criticized the pressure on researchers to produce immediate results. He argued that fundamental discoveries often take time to yield practical applications. "Trying to program research with fixed objectives makes no sense," he said. He noted that politicians often set short-term goals for complex problems, but scientific progress requires foundational understanding first.