In 1927 at the fifth Solvay Council, that reunited all the aristocracy of theoretical physics, Einstein, regarding with solicitude the new-born “quantum mechanics” of Louis de Broglie, Schrödinger, Heisenberg and Dirac, discerned with his usual sagacity an indelible mark that was destined to become, with time, a subject of passionate discussion among those whose vocation is to adulate this enigmatic and capricious personality.In 1926 Born had given the prophetic stroke to the portrait. Turning to probability as to the official factotum (...) of the reconciliation of the continuous and the discontinuous-here, the associated wave and particle-he transmuted the waves of de Broglie and Schr6dinger into an undulatory calculus o f probabilities, deducing, from a surprising principle, consequences that were even more surprising but always verified through experiment. Parting from the idea that the intensity of the wave is the probability of the detection of the particle at a given point and time, Born replaced the classic principle of addition of partial probabilities with his “principle of the addition of partial amplitudes” that are, as in classical optics, represented by “complex” dimensions, with one real part and one imaginary part. In general, the square of the module of the sum of amplitudes will be the probability. This expression contains, of course, the terms “square” and “rectangular.” The first, if they were alone, would give the former law; as for the second, they express the existence of phenomena of interference that are at the origin of the thousand and one well verified paradoxes of the “new mechanics “-the one thousand and first being the one under consideration here. (shrink)

A theoretical and experimental search for the so-called Weyssenhof behavior of a spinning particle, due to the noncollinearity of its velocity and momentum, has been undertaken. Z-independent solutions of Maxwell's equations had previously been produced with a nonzeros z component of the Poynting vector; indeed, Imbert emphasized that the spatial exponential damping of Fresnel's evanescent wave would entail a nonzero value for the integral ε εs z dx dy. Excellent experimental verifications of this point have been obtained by Imbert. Besides (...) having noz component of their momentum, the energy-momentum quanta inside Fresnel's evanescent wave have typical tachyon properties, the imaginary character of theiry component (normal to the reflecting surface) entailing that (in units such thatc=1) theirx component islarger than the energy quanta. Imbert is now planning experiments to test these interesting properties. Thus, the two main aspects of noncollinearity of velocity and momentum of spinning particles would be displayed. (shrink)

A la différence de plusieurs interprétations de la mécanique quantique basées sur la phénoménologie de l'expérimentation macroscopique, celle-ci repose exclusivement sur le formalisme de la mécanique quantique relativiste lui-même. On y assimile le concept de causalité à celui d'une probabilité conditionnelle ayant deux traits spécifiques : « non-séparabilité » des occurrences au sens du calcul quantique des probabilités ; invariance sous les rotations et les retournements d'axes du référentiel spatio-temporel cartésien, impliquant une réversibilité cause-effet. Unlike various interpretations of quantum mechanics (...) based upon the phenomenology of macroscopic experimentation, this one rests entirely upon the formalism of relativistic quantum mechanics per se. The concept of causality is likened to that of a conditional probability endowed with two specific features : « non-separability » of occurrences in the sense of the quantal calculus of probabilities ; invariance under rotations and reversals of axes of the spatiotemporal Cartesian reference frame, entailing cause-effect reversibility. (shrink)