Quantum Theory And Reality


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Quantum Theory And Reality

  1. 1. Quantum Theory and Reality " The Reality! What is the Reality? Ah, what will convey unto thee what the reality is! " ……..Al-Qur'an, Surah Al-Haqqah, (The Reality), 69: 1-3 For thousands of years man has been trying to understand the nature of physical reality, consciousness, the purpose of life, the reality of nature and many, many, mysteries of the life and the universe. For the last 100 years we have seen the introduction of quantum theory, quantum mechanics and quantum physics that have focused on quantum computation to consciousness, parallel universes and the very nature of physical reality. We are not aware of the extraordinary range of scientific and practical applications that quantum mechanics strengthened: almost 30 percent of the United States GNP (gross national product) is based on the inventions made possible by quantum mechanics, such as semiconductors in computer chips to lasers, CD (compact-disc) players, MRI (magnetic resonance imaging) in medical centers. Quantum mechanics was instrumental in predicting positrons (antimatter), understanding radioactivity that lead to nuclear power, explaining superconductivity, and describing interactions such as those between light and matter that lead to the invention of the laser and of radiowaves and nuclei that lead to MRI. Quantum Mechanics Quantum Mechanics is a branch of physics, which deals with the behavior of matter and light on the atomic and subatomic scale. Its concept frequently conflicts with common sense notions. The business of Quantum Mechanics is to describe and account for the world-on the small scale-actually and not as we imagine it or would
  2. 2. like it to be. The world of Quantum Mechanics is strange, fascinating, mysterious and very intellectual. On the other hand the word "Quantum Mechanics" is repelling, boring, uninteresting and very dull. Most of us shy away from the word Quantum Mechanics, whenever it is mentioned. Consider for example the “classical” atom, i.e. the solar system model of the atom as introduced by Rutherford in 1911. The basic flaw with this “classical” atom is that as the orbiting electron circles the nucleus, it should emit electromagnetic waves of an intensity increasing rapidly to infinity in a tiny fraction of a second, as it spirals inwards and plunges into the nucleus. However, nothing like this is observed. Thus our observation contradicts our “classical” physics theory. This is why Quantum theory, which certainly was not wished upon by scientists, was forced upon them despite their great reluctance. They found themselves driven into this strange, and in many ways, philosophically unsatisfying view of the world. Thanks God the real world is neither entirely classical nor quantum. On the “large” scale, the world seems to behave rationally according to the classical theory. However as you go “smaller”, it starts to act in a strange, peculiar way to save itself from extinction. Now what if we were living in an entirely classical (non-quantum) world? The answer is simple. There would be no world, classical or other, to live in. In a purely classical world, the atoms would not exist, as the electrons would be sucked into the nucleus, transforming the world into a concentrated, dense material, in a fraction of a second. One might say that since this awkward quantum theory deals with the very “tiny”, who cares? Wrong. As a matter of fact the very existence of solid bodies, the strength and physical properties of materials, the nature of chemistry, the colors of substances, the phenomena of freezing and boiling, the reliability of inheritance, these, and many
  3. 3. familiar properties, require the quantum theory for their explanations. The World without the knowledge of Quantum Mechanics On the other hand, quantum theory has been an outstanding successful theory and underlies nearly all of modern science and technology. It governs the behavior of transistors and integrated circuits, which are the essential components of electronics devices such as television and computers, as mentioned earlier, and is also the basis of modern chemistry and biology. In short, it is almost impossible to imagine the modern world without the contributions of quantum theory. Quantum theory as we know it today arouse out of two independent later schemes which were innovated by a pair of young remarkable physicists: a 24 year old German, Werner Heisenberg, and an Austrian, Erwin Schrodinger. Heisenberg's uncertainty principle proves that nature does not allow us to measure the position and velocity of a single particle (let alone the whole universe) with perfection, no matter how precise our measuring instruments. Schrodinger developed what is known as Schrodinger equation. This equation states that there is a wave associated with any particle (like the electron), and it is called the wavefunction and it is spread out to fill the whole universe. The wavefunction is stronger in one region, which corresponds to the position of the particle and gets weaker farther away from this region but still exists even far away from the "position" of the particle. Schrodinger equation is very good at predicting how particles like electrons behave under different circumstances. DUAL ASPECTS The subatomic units of matter are very abstract entities, which have a dual aspect. Depending on how we look at them, they appear sometimes as particles, sometimes as waves; and this dual nature is also exhibited by light which can take the form of electromagnetic waves or of particles. It seems impossible to accept that something can be, at the same time, a particle-i.e., an entity confined to a very small volume-and a wave, which is spread out over a large region of space. This contradiction gave rise to the formulation of the quantum theory. Max Planck discovered that the energy of heat radiation is not emitted continuously, but appears in the form of "energy
  4. 4. packets." Einstein called these energy packets "quanta" (quantum is singular) and recognized them as a fundamental aspect of nature. The light quanta are called photons, which are massless and always travel with the speed of light. ISLAMIC PERSPECTIVE In Ayathul Kursi, we read "….His throne includeth the heavens and the earth…" ( Qur'an, 2: 255). From this verse the Muslims understand that Allah (SWT) is present everywhere in the universe. Again we read in Surah Qaaf "… We are nearer to him than his jugular vein."( Qur'an, 50: 16). From this verse the Muslims understand that Allah (SWT) is closer to us than our jugular vein. So what is the Reality? Apparently, there seems to be some contradiction for those who have no knowledge of Duality. A PARTICLE AT TWO PLACES AT THE SAME TIME Let us assume that we are studying the position of a light photon traveling in space. It has been shown that this photon has a wavefunction as introduced by Schrodinger equation. The wavefunction peaks at the position of the photon. Now if this photon encounters a half-silvered mirror, tilted at 45° to the light beam (a half-silvered mirror is a mirror, which reflects exactly half of the light, which impinges upon it, while the remaining half is transmitted directly through the mirror), the photon's wavefunction splits into two, with one part reflected off to the side and the other part continuing in the same direction in which the photon started. The wavefunction is said to be "doubly peaked." Since each "part" of the wavefunction is describing a position that may be light-years away from the other position given by the other "part" of the wavefunction, we can conclude that the photon has found itself to be in two places at once, more than a light-year distant from one another!
  5. 5. Someone might say that this previous assessment is not real. What is happening really is that the photon has a 50 percent probability that it is in one of the places and a 50 percent probability that it is in the other? No, that's simply not true! No matter for how long it has traveled, there is always the possibility that the two parts of the photons' beam may be reflected back so that they encounter one another, for a much awaited "reunion". If it was a simple matter of probability, the photon would be either on one position "OR" the other, and there would not be any need for "reunion" with the other probability. So as long as there is any possibility that the wavefunction will be reduced to one peak again (as it was before the photon hit the half-silvered mirror); the photon in question shall behave as one photon in two places at the same time! In the experiment presented here, a light beam encounters a half-silvered mirror angled 45° to the light beam, splitting the beam into two. The two parts of this light beam is brought back again to the same point (where a second half-silvered mirror is placed) by using a pair of fully-silvered mirrors .Two photocells (A & B) are placed in the direct line of the two beams in order to find the where about of the examined photon. What do we find? If it were merely the case that there were a 50 % chance that the photon followed one route and a 50 % chance that it followed the other, then we should find a 50 % probability that one of the detectors registers the photon and a 50 % probability that the other one does. However, that is not what happens. If the two possible routes are exactly equal in length, then it turns out that there is a 100 % probability that the photon reaches the detector A, lying in the direction of the photon's initial motion and a 0 % probability that it reaches the other detector B (the photon is certain to strike detector A). What does this tell us about the reality of the photon's state of existence between its first and last encounter with a half-reflecting mirror? It seems inescapable that the photon must, in some sense have actually traveled both routes at once! For if an absorbing screen is placed in the way of either of the two routes, then it becomes equally probable that A or B is reached; but when both routes are open (and of equal length) only A can be reached. Blocking off one of the routes actually allows B to be reached! With both routes open, the photon somehow "knows" that it is not permitted
  6. 6. to reach B, so it must have actually felt out both routes. What is the Reality ? (Qur'an, 69: 1-3) EPR PARADOX Locality and non- locality You are spending the summer in Europe. Your mother calls you from California to tell you that you have inherited a large amount of money from your billionaire grandpa. A whole 70 million dollars. You are flying from happiness. What happened in San Francisco - where your mother lives - influenced you seven thousand miles away. Your mum's voice - the cause of your pleasure - had to travel seven thousand miles, and although it took only a tiny fraction of a second to reach your ears, yet it consumed "some" time. So the cause of your pleasure had to travel through space for some time till it influences you. This is called "locality". On the other hand non-locality means that an event at one place shall affect another event, far away from it, instantly. Although this is against special relativity -which prohibits any signal to travel faster than light - it was proved true in quantum mechanics. What is the Reality ? (Qur'an , 69:1-3) The EPR (Einstein-Podolsky-Rosen) Paradox introduces a class of experiments, which turn out to involve some of the strangest consequences of quantum mechanics. This experiment involves a pair of particles, or physical systems, which interact and then move apart. Quantum theory shows that the results of measurements on one particle enable us to predict the results of corresponding measurements on the other particle. That is because both particles were "one" physical system. Now if we perform a measurement on one particle, the wavefunction shall jump to assume the value of the measurement on this particle. But what about the second particle, since this system
  7. 7. was "one" system, this means that a measurement (or jumping) at particle 1 implies an instantaneous measurement (or jumping) at particle 2. Because the experiment involves some advanced physical properties of particles (spin, polarization…), we designed an analogous experiment using colors so the concept of non-locality can be understood easily. (This experiment is not real.) Suppose that we have a white particle. This particle was then split into two particles: a green particle and a magenta particle. Now imagine that the two particles moved in opposite directions at the speed of light for 10 years, so that they eventually were 20 light years apart. Now according to quantum mechanics, any measurement (trying to determine the color of a particle) on particle 1 shall determine the outcome of measurement on particle 2. So if we examined the color of particle 1 and found it to be green, then the other particle is automatically magenta. Now suppose you decided to inspect or measure the color of particle 1 in a red light chamber, and found it yellow (green + red). According to quantum mechanics, at the exact same time, the second particle has turned blue, so that the sum of the colors of the two particles remains white. Now how did particle 2 "know" about particle 1 measurement and how come it was affected by it? What is the Reality? (Qur'an, 69:1-3) SCHRODINGER'S CAT What happens if we designed an experiment where a quantum event would have a direct impact on a large object like…a cat! Imagine a sealed container, so perfectly constructed that no physical influence can pass either inwards or outwards across its walls. With the cat inside the container, there is also a device that can be triggered by some quantum event. The quantum event is the triggering of a photocell by a photon, where the photon had been emitted
  8. 8. by some light source, and then reflected off a half-silvered mirror. The reflection at the mirror splits the photon quantum state (wave function) into two separate parts; one of which is reflected and the other is transmitted through the mirror. The reflected part of the photon wave function is focused on the photocell, so if the photons are registered by the photocell, it has been reflected .In that case, the cyanide is released and the cat is killed. If the photocell doesn't register, the photon was transmitted through the half-silvered mirror to the wall behind, and the cat is safe. Now, let us take the viewpoint of the physicist outside the container. According to the outside observer, no "measurement" has actually taken place, so the quantum state of the entire system is nothing but a linear superposition between alternatives right up to the scale of the cat (Schrödinger equation). Both alternatives must be present in the state. So, according to the outside observer, the cat is in a linear superposition of being dead and alive at the same time! What is the Reality? (Qur'an, 69:1-3)