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Alain Aspect Quotes (1947-)
Physicist
About Alain Aspect
Alain Aspect (born June 15, 1947) is a French physicist who performed the crucial "Bell test experiments" that showed that Albert Einstein, Boris Podolsky and Nathan Rosen's "spooky action at a distance", did in fact appear to be realised when two particles were separated by an arbitrarily large distance. A correlation between their wave functions remained, as they were once part of the same wave-function that was not disturbed before one of the child particles was measured.
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β[In] 1964... John Stewart Bell... discovered inequalities that allow an experimental test of the predictions of local realism against those of standard quantum physics.β
βIn the ensuing decades, experimentalists performed increasingly sophisticated tests of Bellβs inequalities. But these tests have always had at least one βloophole,β...β
βCertainly we do not need quantum mechanics for macroscopic objects, which are well described by classical physics β this is the reason why quantum mechanics seems so foreign to our everyday existence.β
βLa principale difficultΓ© pour vulgariser la physique quantique, c'est qu'on ne sait pas trΓ¨s bien comment en fabriquer des images dans notre monde. C'est en ce sens qu'elle est vraiment contre-intuitive.β
βI 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.β
βThe 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.β
βNow comes the EinsteinβPodolskyβRosen 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...β
β[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 quantum cryptography and quantum networks, on firmer ground.β
βJohn 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 atomic clocks, as well as entangled qubits.β
βAs 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 intellectual freedom, 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.β
βIn 1935, Albert Einstein, Boris Podolsky, and Nathan Rosen (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 otherβdistantβparticle, 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 particleβs physical reality.)β
βWe 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 faster-than-light. ...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.β
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Alain Aspect on History of quantum mechanics 2 quotes
βThe 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 the John Bell was its prophet.β
Alain Aspect on Quantum mechanics 2 quotes
βQuantum mechanics was, and continues to be, revolutionary, primarily because it demands the introduction of radically new concepts to better describe the world. In addition we have argued that conceptual quantum revolutions in turn enable technological quantum revolutions.β
Alain Aspect on Bell's theorem
βThe purpose of the first part is to convince the reader that the formalism leading to Bell's inequalities is very general and reasonable. What is surprising is that such a reasonable formalism conflicts with quantum mechanics. In fact, situations exhibiting a conflict are very rare, and quantum optics is the domain where the most significant tests of this conflict have been carried outβ
Alain Aspect on Mathematics
βNow comes the EinsteinβPodolskyβRosen 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...β
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Alain Aspect on John Stewart Bell
βWe must thank John Bell for having shown us that philosophical questions about the nature of reality could be translated into problems for physicists, where naive experimentalists can contribute.β
Alain Aspect on Niels Bohr
βWe 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 faster-than-light. ...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 complementarity, and at one point he declared... that "Clarity and truth are complementary," and he made all efforts to be as true as possible.β
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β[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.β
About Alain Aspect
Alain Aspect (born June 15, 1947) is a French physicist who performed the crucial "Bell test experiments" that showed that Albert Einstein, Boris Podolsky and Nathan Rosen's "spooky action at a distance", did in fact appear to be realised when two particles were separated by an arbitrarily large distance. A correlation between their wave functions remained, as they were once part of the same wave-function that was not disturbed before one of the child particles was measured.