A family of teachers in Morocco
Serge Haroche was born on September 11, 1944, in Casablanca, Morocco, into a Jewish family with both Sephardic and Ashkenazi roots. His father’s parents, Isaac and Esther Haroche, were teachers in the schools of the Alliance Israélite Universelle, the Paris-based network that brought French language and modern education to Jewish communities across North Africa and the Middle East. His grandfather had been one of the first pupils of the Alliance school in Marrakesh at the end of the nineteenth century; his grandmother had studied at the first Alliance school of all, in Tetouan. They ended their careers as headmaster and headmistress of the Alliance boys’ and girls’ schools in Salé, near Rabat. Serge’s father, Albert, born in 1920, trained as a lawyer in Rabat.
His mother, Valentine, came from a very different world. She was born in Odessa in 1921 to a Jewish family of physicians who left Russia after the Bolshevik revolution and settled in Morocco, where their Russian medical degrees were recognised. Serge grew up speaking Russian and French, surrounded by a close community of Russian Jewish émigrés in Casablanca. Among them was the architect Casimir Zeligson, whose daughter Claudine played with Serge and his brother as children.
From Casablanca to the Latin Quarter
When Morocco became independent in 1956, Haroche’s parents decided, like many Moroccan Jews, to move to France, which they saw as their cultural home. The first winters in Paris were hard for a boy used to Moroccan sunshine, but school was a consolation. At the Lycée Carnot he went straight to the top of his class, and he discovered that with simple calculus he could work out the escape velocity of a rocket and the orbit of a satellite. It was the time of Sputnik, and the realisation that nature obeys mathematical laws, he wrote, never ceased to astonish him.
After two years of preparatory classes at the Lycée Louis-le-Grand, he came first in the national entrance examination for the École Polytechnique in 1963 but chose instead the École Normale Supérieure, which offered a better route into research. There he was taught by Alfred Kastler, Jean Brossel and Claude Cohen-Tannoudji, three founders of modern atomic physics. In 1964 he ran into Claudine Zeligson again by chance in a café in the Latin Quarter; they married in 1965, when both were 21. She became a sociologist at France’s national research centre, the CNRS.
Learning to talk to atoms
Haroche wrote his doctoral thesis under Cohen-Tannoudji, completing it in 1971 at the University of Paris VI. Their “dressed atom” approach treated an atom and the photons around it as one combined system, an idea that both men would use for the rest of their careers. In 1972 to 1973 he spent a year as a postdoctoral researcher at Stanford in the laboratory of Arthur Schawlow, one of the inventors of the laser, where the first tunable lasers were arriving from the young companies of what would become Silicon Valley. With a pulsed dye laser he showed how lasers could reveal fast “quantum beats” in the light emitted by atoms.
Back in Paris in 1973 he began working with Rydberg atoms, atoms in which one electron has been lifted into a giant orbit, making the atom about a thousand times larger than usual and extremely sensitive to microwaves. He became a professor at Paris VI in 1975, taught at the École Polytechnique, spent part of each year at Yale from 1984 to 1993, and with his long-time colleagues Jean-Michel Raimond and Michel Brune built one of the world’s leading laboratories in what is called cavity quantum electrodynamics: the study of atoms interacting with light trapped between mirrors.
A photon in a box
For most of the history of quantum physics, its strangest predictions could only be discussed as thought experiments. Measuring a single photon normally destroys it, since a detector works by absorbing the light. Haroche set out to do what Erwin Schrödinger had thought impossible: to watch a single quantum object evolve, and to observe it without destroying it.
His laboratory at the École Normale Supérieure built a cavity of two superconducting mirrors about three centimetres apart, cooled to a fraction of a degree above absolute zero. The mirrors were so perfectly reflective that a single microwave photon could bounce between them for more than a tenth of a second, travelling a distance comparable to a trip around the Earth. Rydberg atoms were then sent through the cavity one by one. Each atom did not absorb the photon, but its own quantum state was slightly shifted by it, and that shift could be read when the atom came out. In 2007 the team reported that they could follow a single photon in this way, recording its “birth” and “death” in real time, and count the photons in the box, as the Nobel committee put it, as a child counts marbles in a bowl.
Watching Schrödinger’s cat
The same apparatus allowed Haroche to study one of the deepest questions in physics: why the everyday world does not show quantum superpositions. In 1996 his group put a small field of microwave light into a “cat state,” a superposition of two different states at once, named after Schrödinger’s famous cat that is both alive and dead. They then watched it lose its quantum character as it interacted with its surroundings, a process called decoherence. It was the first experiment to observe decoherence happening step by step, and in later years the team reconstructed the full quantum state of such fields and filmed, in effect, the passage from quantum to classical behaviour.
Haroche shared the 2012 Nobel Prize in Physics with the American David J. Wineland, who had approached the same problem from the opposite direction by trapping ions and probing them with light. The prize recognised “ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems.” The two men had long been friends; in 1996 their groups published back-to-back papers on closely related experiments.
Why it matters
Haroche’s experiments turned quantum mechanics from a theory of statistics over many particles into a toolkit for controlling one particle at a time. That is exactly what a quantum computer requires: quantum bits that can be kept in fragile superpositions, manipulated and read out without being destroyed. The techniques of cavity quantum electrodynamics that he and his colleagues developed were carried over, from the early 2000s, to superconducting circuits, where tiny electrical circuits act as artificial atoms coupled to microwave resonators. This “circuit QED” is the architecture of many of today’s leading quantum processors.
His work on non-destructive measurement and decoherence also matters beyond computing. Understanding how quantum states fall apart is the central engineering problem for every quantum technology, from quantum sensors to secure communication, and his experiments supplied the first detailed picture of it.
Teacher and champion of basic science
In 2001 Haroche was elected to the chair of quantum physics at the Collège de France, the Paris institution where professors give free public lectures that anyone may attend, without enrolment or exams. From 2012 to 2015 he served as its administrator, the equivalent of president, overseeing the opening of new laboratories in physics, chemistry and biology. With Jean-Michel Raimond he wrote the textbook Exploring the Quantum: Atoms, Cavities and Photons, published in 2006.
He has been an outspoken defender of long-term, curiosity-driven research. In his Nobel autobiography he credited the freedom he enjoyed as a young scientist at the École Normale, where he could pursue projects without constant proposals and evaluations, and warned that market-style rules threatened that culture. He has served on international scientific committees, including the panel that searched for a new president of the European Research Council in 2020. He was named a Grand Officer of the Legion of Honour in 2017.
Jewish heritage
Haroche describes himself as coming from a Jewish family of mixed Sephardic and Ashkenazi origin, and his family history traces two great Jewish migrations of the twentieth century: the North African Jews educated by the Alliance Israélite Universelle, and the Russian Jews who fled revolution and settled wherever they could practise their professions. His wife Claudine also comes from a family of Russian Jewish émigrés in Casablanca.
The departure of his family from Morocco in 1956 was part of the large movement of Moroccan Jews to France and Israel in the years around independence. He has described his parents’ choice as essentially cultural: they had received and given their children a French education, and France seemed the natural place to go. He is counted among the Jewish Nobel laureates in physics.
Family and legacy
Haroche lives in Paris. He and Claudine have two children: Julien, a physician working in clinical research, and Judith, a lawyer, who has three children. The French singer and actor Raphaël Haroche is his nephew. Haroche describes his laboratory culture as a mixture of self-confidence and self-mockery, and credits his colleagues Raimond and Brune, and generations of students, with an equal share of the work that made his name.
His legacy is the moment when physicists stopped merely imagining quantum experiments and began doing them. By keeping a single photon alive long enough to look at it again and again, Haroche showed that the strange rules of the quantum world could be observed and controlled, one particle at a time. That ability is now the foundation of a worldwide effort to build quantum computers and sensors.
Sources & further reading
Serge Haroche, Biographical, NobelPrize.org · The Nobel Prize in Physics 2012, Popular information, NobelPrize.org · Serge Haroche, Facts, NobelPrize.org · Serge Haroche, Wikipedia · Researched from the sources above and checked against them. Spotted an error? Tell us.
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