What is the best current theory to explain entanglement in quantum mechanics?
475479
here's my guess --\nthat these particles are somehow "connected" . that they do not violate casuality (this one is proveable) or locality....somehow.
361537
the entanglement can only exist if the wave function is undisturbed, so yes. if particle a is observed as having spin +1/2, particle b will be observed as having spin -1/2.
730142
Possibly so. Possibly no. I'd say the Heisenberg uncertainty principle comes foremost into play here. Maybe also Schrödinger's cat. Is it dead or still alive? That would make a significant difference, you know. These questions can't just be taken so lightly. And how could you even consider Y!A as a forum to resolve such complex issues as this? More to the point, even assuming Planck scale dynamics can be fully understood with the mathematical tools we have at hand today, where exactly does that get us? We still don't know what topping to put on our pizza this weekend. Or whether a third eye would make a good chick magnet. Or even whether that darn cat is still alive or dead.... 'tis an enduring mystery. And we wouldn't want to take all the mysterious challenge out of life, now would we?....Meow.
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quantum theory\nn.\nA theory in physics based on the principle that matter and energy have the properties of both particles and waves, created to explain the radiation of energy from a blackbody, the photoelectric effect, and the Bohr theory, and now used to account for a wide range of physical phenomena, including the existence of discrete packets of energy and matter, the uncertainty principle, and the exclusion principle. \nAny of various specific applications of this theory.\n\n\nquantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics. Just as the theory of relativity assumes importance in the special situation where very large speeds are involved, so the quantum theory is necessary for the special situation where very small quantities are involved, i.e., on the scale of molecules, atoms, and elementary particles. Aspects of the quantum theory have provoked vigorous philosophical debates concerning, for example, the uncertainty principle and the statistical nature of all the predictions of the theory.\nRelationship of Energy and Matter\n\nAccording to the older theories of classical physics, energy is treated solely as a continuous phenomenon, while matter is assumed to occupy a very specific region of space and to move in a continuous manner. According to the quantum theory, energy is held to be emitted and absorbed in tiny, discrete amounts. An individual bundle or packet of energy, called a quantum (pl. quanta), thus behaves in some situations much like particles of matter; particles are found to exhibit certain wavelike properties when in motion and are no longer viewed as localized in a given region but rather as spread out to some degree.\n\nFor example, the light or other radiation given off or absorbed by an atom has only certain frequencies (or wavelengths), as can be seen from the line spectrum associated with the chemical element represented by that atom. The quantum theory shows that those frequencies correspond to definite energies of the light quanta, or photons, and result from the fact that the electrons of the atom can have only certain allowed energy values, or levels; when an electron changes from one allowed level to another, a quantum of energy is emitted or absorbed whose frequency is directly proportional to the energy difference between the two levels.\n\nDual Nature of Waves and Particles\n\nThe restriction of the energy levels of the electrons is explained in terms of the wavelike properties of their motions: electrons occupy only those orbits for which their associated wave is a standing wave (i.e., the circumference of the orbit is exactly equal to a whole number of wavelengths) and thus can have only those energies that correspond to such orbits. Moreover, the electrons are no longer thought of as being at a particular point in the orbit but rather as being spread out over the entire orbit. Just as the results of relativity approximate those of Newtonian physics when ordinary speeds are involved, the results of the quantum theory agree with those of classical physics when very large “quantum numbers” are involved, i.e., on the ordinary large scale of events; this agreement in the classical limit is required by the correspondence principle of Niels Bohr. The quantum theory thus proposes a dual nature for both waves and particles, one aspect predominating in some situations, the other predominating in other situations.\n\nEvolution of Quantum Theory\n\nEarly Developments\n\nWhile the theory of relativity was largely the work of one man, Albert Einstein, the quantum theory was developed principally over a period of thirty years through the efforts of many scientists. The first contribution was the explanation of black body radiation in 1900 by Max Planck, who proposed that the energies of any harmonic osci
475801
A good book is called the new quantum universe.  You'll need to give yourself a bit of time to absorb all that information.  But it contains all the basic ideas, formulations and explanations to get started
1047147
hmmm... \n\nWell the book that got me turned on to physics was "The source book on atomic energy"\n\nThis book starts off at newton and goes up to the nuclear reactors and basicly every thing that was known about nuclear technoolgy at the time (the book is about 50 years old).  It is not quantum mechanics, but it is modern physics.  And modern physics is the start to quantum.  It will give you ALL the backround that you need to know to start to really learn quantum. Also it is very easy to read (I read it the summer after my freshman year in college)  \n\nanother serise of book (also not quite to hard quantum yet) are the "Mr Tompkins" series.  he describes things like the atom and relitivity very well and in a hands on approch.  \n\n\nNow for quantum... I did read one decent book, but i can not remeber what it was.  Just go to your local library and do a search for quantum mechanics and pick up the shortest paper back you can find.  they are all written by very smart people and they are writen so that every on can under stand them.  \n\nI am sorry I did not help to much with a Quantum book, but the other two books that I recomended are very good and will put you directely on the right path towards understanding modern physics,  and you can not understand quantum with out understanding modern (actualy there is usualy a bit of quantum is modern physics classes)
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In June 2002 the Ph.D. project of Dr. Warwick Bowen led by Dr. Ping Koy Lam, Prof. Hans Bachor and Dr. Timothy Ralph of the Australian National University achieved (quantum) teleportation of a laser beam. [2]\n\nIt was a successful quantum teleportation experiment involving the use of 'entangled' photons. A target photon was successfully 'scanned', its properties 'copied' onto a transition photon, and finally the photon was recreated at another location of arbitrary distance, proving in essence the theorems proposed by Einstein to explain his 'strange action at a distance'.\n\nScientists teleported atoms in 2004. [3]
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String theory is still quite new in the world of physics, but it has drawn tremendous attention to all physicists around the world. \nFor the last 80 years or so physicists have been trying to find a theory that will combine the theories of quantum mechanics and general relativity. These two theories describe everything in the universe. General relativity does this on the scale of the very large e.g. planets, galaxies and so on. When it comes to subatomic scale, like protons, quarks etc. general relativity breaks down. This is where quantum mechanics is very accurate, but quantum mechanics does not work when applied to the very large objects. \nGeneral relativity basically deals with gravity and has a calm feeling to it. The predictions it makes is always sort of neat and precise.\nQuantum mechanics on the other hand deals with the uncertainty principal and has a very chaotic feel to it.\n\n\nString theory is what physicisits hope and believe might be the theory combines these two super theories. String theory predicts that every particle (even quarks) are made up of much, much smaller particles called strings. They are not really particles, they are actually vibrating strands of energy. Each of these strands vibrate in a different way. \n\nThe mathematics behind string theory works so well that many believe string theory has to be true, but unfortunately there is currently no way to prove string theory with experiment. If string theory is true, then some of our notions of the universe will have to change dramatically. We will have to accept that we actually live in an 11-dimensional universe.
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The problem is that there are not two wavefunctions for entangled particles. There is only one, but that one wave function describes *both* of the particles. So the observation collapses that one wave function as fixes the state of the system. This is one difficulty of the 'particle' view of things. There is too much of a tendency to think of a two particle state as two one particle states. This is wrong.
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In 1957, Hugh Everett III proposed a radical new way of dealing with some of the more perplexing aspects of quantum mechanics. It became known as the Many-Worlds Interpretation.\n\nAccording to this interpretation, whenever numerous viable possibilities exist, the world splits into many worlds, one world for each different possibility (in this context, the term "worlds" refers to what most people call "universes"). In each of these worlds, everything is identical, except for that one different choice; from that point on, they develop independently, and no communication is possible between them, so the people living in those worlds (and splitting along with them) may have no idea that this is going on.\n\nIn this way, the world branches endlessly. What is "the present" to us, lies in the pasts of an uncountably huge number of different futures. Everything that can happen, does, somewhere.\n\nUntil Many-Worlds appeared, the generally accepted interpretation of quantum mechanics was (and perhaps still is) the Copenhagen Interpretation. The Copenhagen Interpretation makes a distinction between the observer and the observed; when no one is watching, a system evolves deterministically according to a wave equation, but when someone is watching, the wavefunction of the system "collapses" to the observed state, which is why the act of observing changes the system. The Copenhagen Interpretation gives the observer special status, not accorded to any other object in quantum theory, and cannot explain the observer itself, while Many-Worlds models the entire observer-observee system.\n\nThe Many-Worlds Interpretation is an interpretation of quantum mechanics, and pertains to quantum events. But it also has implications for macroscopic systems like you and me. Although you may think that there are certain alternatives you would never choose, can you really be sure of that? There are a practically infinite number of versions of you, who have all split off at some time in the past from the path you are now following. There may be versions of you that split off five or ten years ago, or perhaps five minutes after you were born, to whom those choices may not seem unthinkable. But in a very real sense, those people are still "you" (but it can be argued that we should not use the word "are", or even "were"; we need to invent a new kind of tense...)\n\nMany people find the Many-Worlds Interpretation, and the consequences that flow from it, deeply disturbing. This includes a great many physicists. It is also apparent that many physicists, including many who teach physics, do not have a good understanding of Many-Worlds.\n\nHowever, polls have been taken among theorists who study such things, and have revealed that most of them believe that the Many-Worlds Interpretation represents, in some sense, an accurate description of the way the world really is. The polls also show that many of them would rather not discuss the subject.\n\nIt's not hard to see why so many people find these ideas disturbing. For if they are correct, they have profound implications for our understanding of the nature of the Soul, because the Soul (if there is such a thing) must branch along with the worlds that contain it. It would appear that the writings on which many contemporary religions are based make no mention of such an idea.\n\nIt is commonly thought that Many-Worlds is an unprovable hypothesis, experimentally indistinguishable from the Copenhagen Interpretation, but this may not be the case. It may be possible to observe experimentally one of the predicted effects of Many-Worlds: quantum interference between adjacent worlds. It has even been suggested that the Heisenberg Uncertainty Principle derives from this quantum interference; after you make a measurement (which of course splits the world), you can't be sure about the subsequent state of the observed system, because you can't be sur
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For those who understand mathematics, and dare to imagine beyond the usual, quantum mechanics could easily be the most beautiful branch of physics.\n\nQuantum mechanics is a fundamental branch of theoretical physics that replaces Newtonian mechanics and classical electromagnetism at the atomic and subatomic levels. It is the underlying framework of many fields of physics and chemistry, including condensed matter physics, quantum chemistry, and particle physics. Along with general relativity, it is one of the pillars of modern physics.\n\nQuantum mechanics was developed in the first part of the 20th century and was highly successful in explaining the behavior of atoms, molecules and nuclei. Developed between 1900 and 1930 and later combined with the general and special theory of relativity, it revolutionized the concepts of physics. The new concepts, which were the particle properties of radiation, the wave properties of matter, quantization of physical properties and the idea that one can no longer know exactly where a single particle such as an electron is at any one instance were necessary to explain all of the new experimental evidence that was available at the time. For example, quantum mechanics explains the behavior of semiconductors which are used to make the myriad of devices we use every day.\n\nFollowing are the important contributors to the foundation of quantum mechanics and the principles they uncovered.\n\nYear  Researcher    Quantum Mechanics Concept\n1901  Planck        Blackbody radiation\n1905  Einstein      Photoelectric effect\n1913  Bohr          Quantum theory of spectra\n1922  Compton       Scattering of photons off electrons\n1924  Pauli         Exclusion principle\n1925  de Broglie    Matter waves\n1926  Schroedinger  Wave equation\n1927  Heisenberg    Uncertainty principle\n1927  Davison and Germer  Wave properties of electrons\n1927  Born          Interpretation of the wavefunction\n\n[The answer given by the first user (theswarm666x) is foolish. Although, one gives such examples in order to explain students of quantum mechanics what is actually meant by the terms like 'tunneling', you could not and should not use quantum mechanics in such a situation. Quantum mechanics talks about the wave aspect of objects (which is significant only for very small bodies) and waves can travel through walls.]
820204
under quantum mechanics...\nit's a thought experiment, called the EPR paradox...\nthis paradox is more severe or seious than schroedinger's cat paradox...\n\nquantum mechanics says that a motion of a particle can be deermined by its wave function, thus the results of an experiment or probabilities or predictions...\n\nbut E, P and R thought that this is true only with statistical distributions of the particles tested by the experiment (the properties of particles)...
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I'm not sure I follow what you're trying to ask clearly enough, but maybe this will help.\n\nWhen A 'collapses' the wave function, he's affecting it, but not.  He gains the information about the entangled photons, but he hasn't actually changed the state of the photons.\n\nWhen B goes to 'look at' the entangled photons, he also sees the collapse.  However, wavefunctions only collapse because you see them as being in a defined state - it is impossible to look at something without it being collapsed.  B cannot observe photons in jar 1 to be non-collapsed.  By looking at it, it's collapsed.\n\nThere is debate whether these wavefunction collapses are due to our observations or simply a description of our lack of knowledge prior to observation.  Taking Schrodinger's cat... observing the cat does not change whether it is dead or alive, it merely collapses the 'wavefunction' of the cat's existance to being either alive or dead.
101623
What does it mean to be "true"? The quantum theory (I suppose that's what you're asking about) can explain a lot of physical experiments, so, up to a certain extent, it has been proven true. It is also the truest physical theory for small scales up to today.\nScience isn't about finding absolute truths, it's about providing a description of reality that suits your needs. Take newton's gravity laws for example: while proven false in absolute by einstein's relativity, they are still really useful and tought in many places.\nOf course the goal is to one day provide a theory (a description of reality, not "a guess") that explains everything, but for now that's still a dream.
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It sounds like you are talking about an area of science known as quantum mechanics, though you might be referencing subatomic particle theory.  Yes, the math can be a bit much and the conceptualizations a bit forced.  But not knowing you I am hestitant to say no way.  Maybe you could should start out with little thermodynamics.\n\nThe first site below is one called HyperPhysics.  The link will send you straight to the grid on thermodynmics.  Try tapping the buttons, read and little and see if it makes sense.  I suggest you start with kinetics.  If HyperPhysics doesn't do it for you, try Wikipedia.  If you want to leap in head first the last reference is about string theory, tachyons and all that good stuff.  Good luck and heppy learning.
990811
Quantum mechanics is a fundamental physical theory which extends and corrects Newtonian mechanics, especially at the atomic and subatomic levels. It is the underlying framework of many fields of physics and chemistry, including condensed matter physics, quantum chemistry, and particle physics. The term quantum (Latin, "how much") refers to the discrete units that the theory assigns to certain physical quantities, such as the energy of an atom at rest.
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I am trying to give just a brief idea about these questions. Actual explanations need a lot of space. In any case, one can easily search the internet for these things.\n1. Special theory of relativity was combined with quantum mechanics to produce a new branch of physics called 'relativistic quantum mechanics'. This was done mainly by Dirac. He considered the wave functions of particles moving with very high velocities, and used Lorentz transformation equations in his mathematics. He considered also the imaginary (complex) solutions to the basic equations of motion (such as the Schrodinger equation, for example). The main contribution of this 'unification' was the theoretical discovery of anti-particles (which was varified later on from the experimental discovery of positrons).\n2. The 'unification' of general theory of relativity and quantum mechanics leads to the branch called 'quantum gravity'. The basic problem with this unification is the matching of length scales at which these two theories work. Quantum mechanics is designed and valid for subatomic length-scales, whereas, the general theory of relativity, which is the theory of gravity, deals with massive objects and large (astronomical) length-scales. Presently, scientists are looking for a suitable wavefunction for the universe, which is expected to provide information about the universe in the same way as the wavefunction of an electron gives many information about it.\n3. Feynman reconstructed almost the whole of quantum mechanics and electrodynamics in his own way, deriving a way to analyze atomic interactions through simple diagrams (now known as Feynman diagrams), a method that is still used widely. QED was the theory to which Feynman diagrams were first applied. For his work on quantum electrodynamics, Feynman was one of the recipients of the Nobel Prize in Physics for 1965, along with Julian Schwinger and Shin-Ichiro Tomonaga.\n\nI would also like to comment on the answers given by other users, such as Smart prash: \n1. In question 1 the user is asking about Dirac's relativistic quantum mechanics, and not about Bohr's elementry quanrum mechanics.\n2. Please don't get confused. Quarks are not coloured at all (how can they be?). Colour of a quark is just one of the many quantum numbers that is used in a way to number them in terms of their different energies. Moreover, the question is about QED (quantum electrodynimics), and the colour quantum number is a concept from QCD (quantum chromodynamics).