I really enjoyed Serge Haroche's perspective in PRX Quantum: Laser, Offspring and Powerful Enabler of Quantum Science, part of the APS' International Year of Quantum collection. Haroche is a French physicist famous for his work on CQED measuring individual MW photons via their interaction with Rydberg atoms passing through a cavity. Here's an excerpt from Haroche's Nobel lecture (2012)¹:

We have realized the nondestructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of “Schrödinger cat” states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits.

And another excerpt on his prize from Nature Physics²

"We never experiment with just one electron or atom or (small) molecule. In thought-experiments we sometimes assume that we do; this invariably entails ridiculous consequences", wrote Erwin Schrödinger in 1952.

And yet, sixty years later, the Nobel Prize in Physics has been awarded for experimental developments that have made the measurement and control of individual atoms and photons possible. Far from being thought ridiculous, precision experiments using a single photon or a single atom are the basis of today's time and frequency standards – and of tomorrow's quantum technologies.

Haroche's PRXQ article is a fantastic brief history of light-matter physics since the Stern-Gerlach experiment in 1922, weaving in the technological advances in (and precursors of) the laser. To whet your appetite I will reproduce just a few key passages that jumped out to me.

In the abstract of the paper describing theoretically the optical pumping procedure, which he was going to demonstrate two years later with J. Brossel and J. Winter, Kastler made a remark, which shows the modesty of a scientist careful not to oversell his ideas. He wrote "even if we manage to achieve the experimental conditions for irradiation cooling, this effect will remain a scientific curiosity rather than a practical means of achieving low temperatures” Kastler thus foresaw that light opened up previously unsuspected possibilities for manipulating and cooling matter.

[...]

The optical molasses experiment was performed by Steven Chu et al. at Bell labs in 1985. They applied the six-beam laser configuration to the atoms emerging from a Zeeman slower and obtained an optical molasses of about one billion atoms, a bright cloud of cold atoms fluorescing at the intersection of the laser beams. Phillips and his group quickly reproduced the experiment (Fig. 3) and measured in 1986 the temperature of the molasses by a time-of-flight method [45,46]. They switched off the lasers,letting the atoms in free fall and detected them by the fluorescence induced by a resonant probe laser placed below the molasses. The delay between the release of the atoms and the appearance of the fluorescence yielded the average atomic velocity and hence the temperature of the molasses, which was found to be of the order of 1 μK, i.e., 2 orders of magnitude smaller than the Doppler cooling limit. Unexpectedly, laser cooling had reached an uncharted territory, bringing down the absolute temperature to a range at least 3 orders of magnitude smaller than could be achieved with He cryostats! It was no longer what Kastler had called a “scientific curiosity.”

The reason for this unexpected cooling was the 'Sisyphus' cooling mechanic. And then the fascinating conclusion, highlighting the impact of the academic genealogy:

XIII. CONCLUSION: FROM PAST LEGACY TO FUTURE PROSPECTS OF LASER PHYSICS

I have outlined the long sequence of experiments that led from the origins of the laser to the latest developments in quantum optics made possible by this extraordinary instrument. The lineage of scientists who have participated in this story have—from generation to generation—drawn inspiration from each other’s work, in an ongoing pursuit of new knowledge motivated by sheer curiosity. O. Stern’s legacy is particularly striking. The discoverer of the electron spin has been the master of O. Frisch, who was the first to deflect atoms with light, and the postdoctoral mentor of I. Rabi who founded later the Columbia atomic physics group. N. Ramsey, Rabi’s student, has trained in turn D. Wineland and D. Kleppner. The latter has been the thesis advisor of W. Phillips and a mentor for C. Wieman, E. Cornel, and W. Ketterle. J. Schwinger, another student of Rabi and the co-discoverer with Feynman and Tomonaga of quantum electrodynamics, was the thesis advisor of R. Glauber who laid in the 1960s the theoretical foundations of quantum optics. [continued]

I have not read such a great overview of scientific progress in (broad strokes) my field before, and I found it very enlightening.

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