Climério Paulo da Silva Neto, <i>Materializing the Foundations of Quantum Mechanics: Instruments and the First Bell Tests</i> Cham: Springer Nature, 2023. Pp. 73. ISBN 978-3-031-29796-0. £39.99 (softcover).

With the promise of quantum computers on the horizon, interest in quantum foundations and the rise of the second quantum revolutionconcerned with the control and detection of individual quantum systemshas grown considerably in recent years.Despite this, research into the process that led the prewar Gedankenexperiments (thought experiments), conceived in debates between the founding fathers of quantum mechanics, to be transformed into real post-war experiments, has paid little attention to the instruments themselves, even though they are essential to the practice.Silva Neto addresses this gap by examining, in a broad framework extending to the mid-1980s, the material culture of the first significant experiments in the field of quantum foundations, the tests of Bell's inequalities.Silva Neto begins with a concise yet elegant presentation of the origins of these tests, rooted in the 1935 EPR debate and John Bell's 1964 theorem, which allowed quantum mechanics to be experimentally tested against local hidden-variable theories.The first of a series of progressively more stringent Bell's experiments followed in 1972.In the three main chapters of his book, Silva Neto then systematically explores the origins and developments of their key components: the sources of entangled photons, the analysers and the detection sets.After the Second World War, three sources of entangled photons emerged: positron annihilation, photon cascades in atomic beams and spontaneous parametric downconversion.Silva Neto shows that these advances stemmed from a deeper understanding of light-matter interactions.The first two sources, based on pre-war research, became linked to military R & D during the Cold War, particularly in cyclotron research, microwave spectroscopy and quantum electronics, which was crucial for developing masers and lasers.These last technologies paved the way for the third source, developed in the 1960s and incorporated into Bell's inequalities experiments in the 1980s, which has become central to quantum communication and computing.The availability of analysers significantly influenced the design and results of various experiments.Along with the question of the unreliability of analysers for high-energy photons (gamma rays), Silva Neto focuses on the pile-of-plates polarizers used in Bell's first test, as well as the cube beam splitter introduced in the 1980s for more accurate measurements.These technologies benefited from the post-First World War creation of optics institutes in the United States, the Soviet Union and Western Europe, which, by