Physicists From France

"The supreme Being is everywhere; but He is not equally visible everywhere. Let us seek Him in the simplest things, in the most fundamental laws of Nature, in the universal rules by which movement is conserved, distributed or destroyed; and let us not seek Him in phenomena that are merely complex consequences of these laws."

"Everything is so arranged that the blind logic of mathematics executes the will of the most enlightened and free Mind."

"It is only mental habit that prevents us from realizing how miraculous it is that motion can be passed from one body to another. Once our eyes have opened, nothing is so striking. For those who have never thought about it, it doesn't seem mysterious; by contrast, those who have meditated on it may despair of ever understanding it."

"One should not be deceived by philosophical works that pretend to be mathematical, but are merely dubious and murky metaphysics. Just because a philosopher can recite the words lemma, theorem and corollary doesn't mean that his work has the certainty of mathematics. That certainty does not derive from big words, or even from the method used by geometers, but rather from the utter simplicity of the objects considered by mathematics."

"Research into motion was not to the liking (or perhaps not within the scope) of the ancients, so that we may consider it as a completely new science. How could the ancients have discovered the laws of moiton, given that some philosophers reduced all their speculations about motion to sophistic disputes, whereas others denied that motion existed at all?"

"La vie n'est bonne qu'à deux choses : à faire des mathématiques et à les professer. (The only two good things in life are doing mathematics and teaching it.)"

"In many different fields, empirical phenomena appear to obey a certain general law, which can be called the Law of Large Numbers. This law states that the ratios of numbers derived from the observation of a very large number of similar events remain practically constant, provided that these events are governed partly by constant factors and partly by variable factors whose variations are irregular and do not cause a systematic change in a definite direction."

"That which can affect our senses in any manner whatever, is termed matter."

"Experiments with time-like separation... were only possible about twenty years after the first experiments by Aspect."

"[W]e obtain the same correlations of polarizations as in Aspect's first experiments."

"The second statement relates... that a common source for both photons of an entangled pair is a common feature in all Aspect-type experiments. ...[T]hese ...insights are sufficient to develop a model of photon entanglement accounting for all features in the experiments."

"One of the most puzzling results in modern physics, based originally on... EPR... is the apparent non-locality of measurements in . The experiments performed on pairs of entangled photons, beginning with the experiments by Alain Aspect in 1982, seem to prove... that the two measurements are not independent. The measurements are usually interpreted in terms of the Bell inequalities which assert that their violation, corresponding to the experimental results and... predictions of quantum optics, amounts to a nonlocal connection... There has been... debate on whether such... implies superluminal effects... for example Maudlin's book. The present consensus is that... no information travels faster than light..."

"[W]e... approach... from a new angle. ...[W]e start from the assumption that quantum optics contains, in its mathematical formalism, the answer.... [T]he conceptual difficulty... has been due to the lack of transparency in its mathematical framework. We can formulate this hypothesis in two distinct statements: 1. Quantum optics is complete. 2. The connection between the two photons is due to their common source."

"[B]y closing the two main loopholes at the same time, three teams have independently confirmed that we must definitely renounce local realism... Although their findings are... no surprise, they crown decades of experimental effort. The results... place several fundamental quantum information schemes... as device-independent and s, on firmer ground."

"In 1935, Albert Einstein, Boris Podolsky, and (EPR) wrote a now famous paper questioning the completeness of the formalism of quantum mechanics. Rejecting the idea that a measurement on one particle in an entangled pair could affect the state of the other—distant—particle, they concluded that one must complete the quantum formalism in order to get a reasonable, "local realist," description of the world. This view says a particle carries... locally, all the properties determining the results of any measurement... (The ensemble of these properties constitutes the particle’s physical reality.)"

"[In] 1964... John Stewart Bell... discovered inequalities that allow an experimental test of the predictions of local realism against those of standard quantum physics."

"John Bell devoted most of his efforts to conceptual and theoretical questions. Would he have liked that I also stress the importance of the technological revolutions that were, and will be, enabled by the conceptual revolutions? I cannot tell, but we know that he started his career in accelerator design, and that he always showed a profound respect for technological achievements. I like to think that he would have loved quantum-jumps-based s, as well as entangled s."

"Certainly we do not need quantum mechanics for macroscopic objects, which are well described by classical physics – this is the reason why quantum mechanics seems so foreign to our everyday existence."

"As a witness of that period, I am also deeply convinced that John Bell indirectly played a crucial role in the progress of the application of quantum mechanics to individual objects, microscopic and mesoscopic. The example of his , that had led to the recognition of the importance of entanglement, was no doubt an encouragement to those who were contemplating the possibility of developing new approaches, beyond the so-efficient paradigm developed decades earlier. His example opened the gate for new quantum explorations."

"In the ensuing decades, experimentalists performed increasingly sophisticated tests of Bell’s inequalities. But these tests have always had at least one “loophole,”..."

"I think it is not an exaggeration to say that the realization of the importance of entanglement and the clarification of the quantum description of single objects have been at the root of a second quantum revolution, and that John Bell was its prophet. And it may well be that this once purely intellectual pursuit will also lead to a new technological revolution."

"On graduating from the school, a studious young man who would withstand the tedium and monotony of his duties has no choice but to lose himself in some branch of science or literature completely irrelevant to his assignment."

"Now comes the Einstein–Podolsky–Rosen entangled state. Now I see faces, people saying, "Oh..?" Don't worry! When you go to the concert, you don't need to be able to read the music, to enjoy the music. ...So here... [are] equations. It's a pleasure for my colleague physicists. If you can't read the equation, listen to me. I'm not going to sing, but... listen to the words... the words are... a way of describing the equations, and you don't need to know the mathematics..."

"In the labs, the young make things move, and the older ones follow like parents evolving with their children."

"We pretend that if I get result +1 here, immediately the photon there is in the state |x>, but if I find -1, immediately the other photon assume[s] another state of polarization... [T]his image is not acceptable for Einstein because it seems as [though] something is going . ...It is by this ...reasoning that Einstein said... "If you want to make sense of this correlation at a distance, you have to accept that before they arrive at the measuring apparatus, the particles have already a property determining the outcome." ...Bohr disagreed immediately. ...I don't know anybody who finds Bohr's reply understandable. It's not a joke, what I'm going to say, although it sounds [like] a joke. Bohr is so cautious in his wording that he makes it almost impossible to understand... Bohr insisted on... complimentarity, and at one point he declared... that "Clarity and truth are complimentary," and he made all efforts to be as true as possible."

"La principale difficulté pour vulgariser la physique quantique, c'est qu'on ne sait pas très bien comment en fabriquer des images dans notre monde. C'est en ce sens qu'elle est vraiment contre-intuitive."

"The most remarkable feature of Bell's work was undoubtedly the possibility it offered to determine experimentally whether or not Einstein's ideas could be kept. The experimental tests of Bell inequalities gave an unambiguous answer: entanglement cannot be understood as usual correlations, whose interpretation relies on the existence of common properties, originating in a common preparation, and remaining attached to each individual object after separation, as components of their physical reality."

"... à plusieurs époques on a pu croire que l'optique était une science finie, où le dernier mot avait été dit, ou presque. Chaque fois la découverte de faits nouveaux, le renversement ou l'élargissement des théories admises, venaient rappeler que la science n'est jamais finie. Cette impression qu'une science est terminée s'est produite bien des fois, dans diverses branches du savoir humain; elle a eu souvent pour cause une explosion de découvertes faites par un homme de génie ou par un petit groupe d'hommes, en un temps si court que les esprits moyens avaient de la peine à suivre et avaient l'inconscient désir de reprendre haleine, de s'habituer aux choses inattendues qui venaient de leur être révélées. Comme éblouis par ces vérités nouvelles, ils ne pouvaient voir ce qui était au-delà. Parfois un siècle entier n'a pas suffi à produire cette accoutumance."

"My whole existence has been devoted to science and to teaching, and these two intense passions have brought me very great joy."

"There you have, then, a theoretical physics which is neither the theory of a believer nor that of a nonbeliever, but merely and simply a theory of a physicist; admirably suited to classify the laws studied by the experimenter, it is incapable of opposing any assertion whatever of metaphysics or of religious dogma, and is equally incapable of lending effective support to any such assertion."

"Agreement with experiment is the sole criteria of truth for a physical theory."

"The one who contributed most to break down the barrier between physical method and metaphysical method, and to confound their domains, so clearly distinguished in the Aristotelian philosophy, was surely Descartes."

"A physical theory reputed to be satisfactory by the sectarians of one metaphysical school will be rejected by the partisans of another school."

"« La Logique peut être patiente, car elle est éternelle. » ("Logic can be patient because it is eternal.") ibid. p. 150"

"The first question we should face is: What is the aim of a physical theory? To this question diverse answers have been made, but all of them may be reduced to two main principles: "A physical theory," certain logicians have replied, "has for its object the explanation of a group of laws experimentally established." "A physical theory," other thinkers have said, "is an abstract system whose aim is to summarize and classify logically a group of experimental laws without claiming to explain these laws... Now these two questions — Does there exist a material reality distinct from sensible appearances? and What is the nature of reality? — do not have their source in experimental method, which is acquainted only with sensible appearances and can discover nothing beyond them. The resolution of these questions transcends the methods used by physics; it is the object of metaphysics. Therefore, if the aim of physical theories is to explain experimental laws, theoretical physics is not an autonomous science; it is subordinate to metaphysics... Now, to make physical theories depend on metaphysics is surely not the way to let them enjoy the privilege of universal consent."

"Every time people cite a principle of theoretical physics in support of a metaphysical doctrine or physical dogma, they commit a mistake, for they attribute to this principle a meaning not its own, an import not belonging to it."

"[U]n symbole n'est, à proprement parler, ni vrai, ni faux; il est plus ou moins bien choisi pour signifier la réalité qu'il représente, il la figure d'une manière plus ou moins précise, plus ou moins détaillée..."

"In fact, without any exaggeration, the current mechanism of money creation through credit is certainly the "cancer" that's irretrievably eroding market economies of private property."

"A theory is only as good as its assumptions. If the premises are false, the theory has no real scientific value. The only scientific criterion for judging the validity of a scientific theory is a confrontation with the data of experience."

"Too many theorists have a tendency to ignore facts that contradict their convictions."

"Anyone who dares to speak about an aether is regarded as an ignorant and backward mind and he can only lose his credibility in scientific circles, although in reality those who criticize him use the same concept of intermediate medium in other words, whether it be fields, an associated fluid, a probability fluid, a pilot fluid, a quantum fluid, etc."

"La soumission aux données de l'expérience est la règle d'or qui domine toute discipline scientifique."

"Any author who uses mathematics should always express in ordinary language the meaning of the assumptions he admits, as well as the significance of the results obtained. The more abstract his theory, the more imperative this obligation. In fact, mathematics are and can only be a tool to explore reality. In this exploration, mathematics do not constitute an end in itself, they are and can only be a means."

"Ce n'est point l'observation mais la théorie qui m'a conduit à ce résultat que l'expérience a ensuite confirmé."

"Dans le choix d'un système, on ne doit avoir égard qu'à la simplicité des hypothèses; celle des calculs ne peut être d'aucun poids dans la balance des probabilités. La nature ne s'est pas embarrassée des difficultés d'analyse; elle n'a évité que la complication des moyens. Elle paraît s'être proposé de faire beaucoup avec peu : c'est un principe que le perfectionnement des sciences physiques appuie sans cesse de preuves nouvelles."

"Je ne trouve rien de si pénible que d'avoir à mener des hommes."

"Both the uncertainty principle and the negentropy principle of information make Laplace's scheme [of exact determinism] completely unrealistic. The problem is an artificial one; it belongs to imaginative poetry, not to experimental science."

"The laws of classical mechanics represent a mathematical idealization and should not be assumed to correspond to the real laws of nature. … We now have to realize that errors are inevitable (..) a discovery that makes strict determinism impossible."

"With Heisenberg's uncertainty principle, the fundamental role of experimental errors became a basic feature of physics."

"Si l'on s'est quelquefois égaré en voulant simplifier les éléments d'une science, c'est qu'on a établi des systèmes avant d'avoir rassemblé un assez grand nombre de faits. Telle hypothèse, très-simple quand on ne considère qu'une classe de phénomènes, nécessite beaucoup d'autres hypothèses lorsqu'on veut sortir du cercle étroit dans lequel on s'était d'abord renfermé. Si la nature s'est proposé de produire le maximum d'effets avec le minimum de causes, c'est dans l'ensemble de ses lois qu'elle a dû résoudre ce grand problème. Il est sans doute bien difficile de découvrir les bases de cette admirable économie, c'est-à-dire les causes les plus simples des phénomènes envisagés sous un point de vue aussi étendu. Mais, si ce principe général de la philosophie des sciences physiques ne conduit pas immédiatement à la connaissance de la vérité, il peut néanmoins diriger les efforts de l'esprit humain, en l'éloignant des systèmes qui rapportent les phénomènes à un trop grand nombre de causes différentes, et en lui faisant adopter de préférence ceux qui, appuyés sur le plus petit nombre d'hypothèses, senties plus féconds en conséquences."