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Uk quantum teleportation3 Presentation Transcript

  • 1. QUANTUM TELEPORTATION QUANTUM TELEPORTATION What’s Quantum Teleportation? Qubits and Quantum Computers
  • 2. TABLE OF CONTENTS TABLE OF CONTENTS The theory Introduction to the Quantum Teleportation Quantum communication History, applications, further information back to the introduction
  • 3. WHAT IS QUANTUM TELEPORTATION? WHAT IS QUANTUM TELEPORTATION? Before giving a “complete definition” it is necessary to emphasize that it is a technique of communication that takes advantage of some unique aspects of the Quantum Mechanics a physical theory that describes the behaviour of the electromagnetic radiation, the matter and their interactions, particularly with regard to the phenomena typical of the length or energy scales of the atomic and subatomic particles.
  • 4. Development of the Quantum Mechanics Development of the Quantum Mechanics The Quantum Mechanics developed in the first half of the twentieth century, due to the inconsistency of the classical mechanics and its inability to represent the experimental reality, with particular reference to the light and the electron. The name "Quantum Mechanics", was introduced by Max Planck in the early twentieth century; it is based on the fact that quantities such as energy or angular momentum of some physical systems can change in a discrete manner namely assuming only certain values, named: "QUANTA". "QUANTA".
  • 5. The basic characteristic that distinguishes the Quantum Mechanics from the Classical Mechanics is that: in the Quantum Mechanics the electromagnetic radiation and the matter are both described as a wave phenomenon and, at the same time, as particles, in contrast to the Classical Mechanics, where, for example, the light is described only as a wave and the electron only as a particle. This unexpected and non intuitive property called: “wave-particle duality” “wave-particle duality” is the main reason for the failure of all classical theories developed until the nineteenth century.
  • 6. SOME EXPERIMENTAL SITUATIONS IN WHICH THE SOME EXPERIMENTAL SITUATIONS IN WHICH THE "CLASSICAL PHYSICS" FAILS: "CLASSICAL PHYSICS" FAILS: Black body radiation Photoelectric Effect Atomic spectral lines Wave properties of the electrons QUANTUM MECHANICS PROVIDES SOLUTIONS WITH: QUANTUM MECHANICS PROVIDES SOLUTIONS WITH: Planck's theory of the radiation of a black body Einstein's explanation of the photoelectric effect Bohr's model of the hydrogen atom Wavelength of Louis de Broglie
  • 7. Max Planck found that the energy of the radiation emitted or absorbed by a black body is not emitted and absorbed continuously but in discrete quantities called “quanta”. The main concept of his theory was based on the fact that: each elementary oscillator (the electrons within the atom) could exchange energy with the environment only in the packets form given by: E = hʋ where: h = 6,63 × 10-34 J·s = 6,63 x 10-27 erg·s is the Planck's constant ʋ is the frequency of the oscillator. Albert Einstein was the first to recognize that this energy quantization of the emitted or absorbed radiation is a general property of the electromagnetic radiation, thinking of it as a set of photons with energy: E = hʋ Niels Bohr applied the ideas of Einstein, about energy quantization, at the energy of an atom. He proposed a model of the hydrogen atom which was a spectacular success in the calculation of the wavelengths of the radiation emitted by the hydrogen atom.
  • 8. Wave – Particle Duality Wave – Particle Duality WAVE AND PARTICLE NATURE OF THE LIGHT WAVE AND PARTICLE NATURE OF THE LIGHT Schematic summary Does the light consist of particles or waves? The answer depends on the type of observed phenomena.
  • 9. The most common luminous phenomena observed, such as: reflection, refraction, interference and diffraction can be explained as wave phenomena. However, the light that usually we imagine as a wave shows also particle properties when it interacts with the matter as demonstrated by the: photoelectric effect and scattering Compton. The same “wave-particle” duality is also valid for the electrons.
  • 10. Wave – Particle Duality Wave – Particle Duality WAVE NATURE OF THE MATTER WAVE NATURE OF THE MATTER The electrons (and matter in general), which we usually think as particles, have also wave properties of interference and diffraction.
  • 11. Louis de Broglie in 1924 stated that all the particles had wave properties. He affirmed that the wavelength associated with the wave of matter was inversely proportional to the mass “m” of the particle and to its velocity “v”, so that: h λ= mv where “h” is Planck's constant. The product of mass and velocity takes the name of “momentum” p of the particle, then the equation can be reformulated as “de Broglie’s relation” in the following way: h λ= p
  • 12. The wave nature of the electrons was revealed showing that the electron beam can be diffracted. The experiment was made for the first time in 1925 by two American scientists, Clinton Davisson and Lester Germer. They sent a beam of fast electrons against an isolated crystal of nickel. The regular arrangement of the atoms in the crystal acts as a grating, capable of diffracting the waves. Therefore a diffraction image was observed. G.P.Thomson, in 1927, operating at Aberdeen, Scotland, showed that an electron beam produced a diffraction image passing also through a thin foil of gold, as shown in the figure:
  • 13. Thus even the electron, like the photon, reveals a double behaviour. It is not a quite classical particle, but it can have a detectable wave behaviour. The wavelength associated with it is inversely proportional to its momentum.
  • 14. The “de Broglie’s relation” also applies to the photons: λ = c/ν = hc/hν = hc/E = h/(E/c) = h/p In fact, the momentum of a photon is related to its energy by the relation: p = E/c
  • 15. CONCLUSION We can conclude by saying that "All holders of momentum and energy: electrons, atoms, light, sound and so on, have corpuscular and wave characteristics”. back to the table of contents
  • 16. COMPARISON BETWEEN CLASSICAL MECHANICS AND COMPARISON BETWEEN CLASSICAL MECHANICS AND QUANTUM MECHANICS QUANTUM MECHANICS Classical mechanics is a physical theory of deterministic nature. It is governed by the principle of causality. Quantum mechanics is a physical theory of probabilistic nature. It is based on the concept of probability and observation.
  • 17. Basically: According to the Classical Mechanics, due to the discoveries of Newton and Galileo Galilei, if you know the properties of a body (mass, shape, etc.), its initial conditions of motion (position, velocity, etc.) and the external conditions (force fields, etc.), it is possible to determine, exactly, its behavior instant by instant. Therefore within the framework of the Classical Mechanics the principle of causality applies; namely, in nature nothing happens by chance, each event is determined by an identified cause. The nature of the Quantum Mechanics is indeterministic; namely, it is based on the concept of probability and observation. For example, if somebody wants accurately to know the location of an electron in an atom, he will never know the speed and vice versa.
  • 18. The famous example of Schrödinger's cat clarifies The famous example of Schrödinger's cat clarifies the nature of Quantum Mechanics. the nature of Quantum Mechanics.
  • 19. In this example, a cat is closed in a box, with a machine connected to a bottle containing poison. The machine starts when a radioactive element decays, breaking the bottle containing poison. From the outside, the cat inside the box can be alive or dead, because you don’t know if the radioactive element has decayed or not. According to the Quantum Mechanics, the cat is in both states “alive and dead”; it is in a superposition of states: state "alive" and state "dead". Only the observation phase freezes the state of the cat, determining its fate.
  • 20. In order to speak of Quantum Teleportation it is necessary to take into account the wave and the corpuscular nature of electromagnetic radiation and of matter. That is to say: “Wave – Particle” duality for the light and the matter The wave and the corpuscular nature of the particles is related by the “Heisenberg’s Uncertainty Principle”
  • 21. Formulated by the German scientist Werner Heisenberg in 1927, this principle states that: “if the uncertainty Δx on the position x of a particle is very little, the uncertainty Δp on the momentum p is large and vice versa " Representation of the Heisenberg’s Uncertainty Principle: a) b) a) The x position of the particle is badly defined; this allows to specify its momentum p, represented by the arrow, with acceptable accuracy. b) The x position of the particle is well defined; this prevents to specify precisely its momentum p.
  • 22. The math expression of the principle is: Δx·Δp ≥ h/4π or: Δx·Δp ≥ ћ/2 According to the Heisenberg’s Uncertainty Principle we can say that: “it's impossible to know simultaneously and with accuracy the momentum and the position of a particle”.
  • 23. The same uncertainty affects the measurement of energy E and time t: simultaneous ΔE·Δt ≥ ћ/2 This means that: “in a very short time the energy is not defined”.
  • 24. In other words: “the product of the uncertainties of two simultaneous measurements can not be less than a given constant”. back to the table of contents
  • 25. Quantum communication Quantum communication According to Quantum Teleportation it’s possible to transfer the quantum state of a particle (for example, the state of polarization, in the case of a photon) to large distances. It is not the particle itself to be transferred but the "receiver" takes exactly the same state of polarization of the "transmitter". The Heisenberg’s Uncertainty Principle prohibits the exact knowledge of the state of the transmitted photon, but a property called "entanglement" makes sure that this is not a problem for the teleportation.
  • 26. STAR TREK TELEPORTATION ALLOWS: the disappearance of an object from one location and the simultaneous reappearance of the same object in another position of the space, without having to travel boring intermediate kilometers and without any vehicle.
  • 27. In science fiction stories Teleportation allows to make travels more comfortable than those made with an ordinary spacecraft, but this involves the violation of ​ the speed limits, imposed by the theory of the relativity. According to this theory nothing can travel faster than light. In the science fiction teleportation procedure varies from story to story and generally takes place in the following way: the original object to teleport is subjected to a scan to extract the necessary information to describe it. A transmitter transfers the information to a receiving station, and this is used to get an exact replica of the original. In some cases, the matter, that composes the original, is also transferred to the receiving station, as some type of energy. In other cases, the replica of the original uses atoms and molecules already present at the place of arrival.
  • 28. According to Quantum Mechanics, a similar impossible even theoretically, in fact: teleportation is the Heisenberg’s Uncertainty Principle declares the impossibility of knowing at the same time, with arbitrary precision, the position and the velocity of a particle. A perfect scanning of the object involves the knowledge, without uncertainty, of the position and the velocity of each atom and each electron, then teleportation is impossible. Heisenberg’s principle is also applied to other pairs of quantities and this expresses the impossibility of measuring, without error, the quantum state of an object. All these difficulties, in Star Trek, are overcome by the prodigious "Heisenberg’s compensator".
  • 29. BUT The science-fiction dream of "projecting" objects from one place to another, is now a reality, at least for light particles: photons although it remains, for now, still a fantasy for macroscopic objects.
  • 30. QUANTUM TELEPORTATION QUANTUM TELEPORTATION Definition: Definition: It is a technique of communication within Quantum Informatics “this is a group of calculation methods and their study that use the QUANTA to store and process information”. The technique of Quantum Teleportation allows, under certain restrictions, the transfer of a quantum state, such as the state of polarization of the photons, the spin state of the electrons or the excitation state of the atoms, to a point arbitrarily far. This involves the effect called QUANTUM ENTANGLEMENT
  • 31. It can be said that: by Quantum Teleportation there is not a transfer in the same way as in Star Trek, but it is possible, through the phenomenon of entanglement to transfer (instantly) "features“ (quantum states) of photons, atoms, ions, in other photons, atoms, ions placed at any distance.
  • 32. QUANTUM ENTANGLEMENT QUANTUM ENTANGLEMENT The quantum entanglement was suggested for the first time in 1926 by Erwin Schrödinger, who was also the first to introduce in 1935 the term "entanglement" Quantum entanglement is a quantum phenomenon, which has no classic equivalent. According to this phenomenon, each quantum state (e.g.: polarization of the photons, spin state of the electrons) of two or more physical systems depends on the state of each of them, even if they are spatially separated. The quantum entanglement implies the presence of remote correlations between the observable physical quantities of the involved systems, so that the non-local character of quantum theory is established. The phenomenon of entanglement therefore violates the "principle of locality" in which what happens in one place can NOT immediately affect what happens in another place. Albert Einstein, despite the important contributions given to the quantum theory, never accepted that a particle could instantaneously influence another particle. Therefore he tried to prove that the violation of locality was only apparent, but, from time to time, his attempts were clinched by his opponents .
  • 33. In 1982 the physicist Alain Aspect, with a series of sophisticated experiments demonstrated the existence of the entanglement, and then the inconsistency of the position of Einstein. In October 1998, the phenomenon of the entanglement was finally confirmed by the success of a teleportation experiment performed by the Institute of Technology (Caltech) in Pasadena, California.
  • 34. LEARN MORE ABOUT “ENTANGLEMENT” LEARN MORE ABOUT “ENTANGLEMENT” If two particles interact for a certain period of time and then they are separated, when one of them is stimulated, so that it changes its state, instantly a similar stress is manifested on the second particle, whatever the distance between the particles; in other words, the second particle changes instantaneously its state. This phenomenon is called "Phenomenon of Entanglement". A simple experiment about the "Phenomenon of Entanglement”: two particles “twins” are launched in opposite directions. If the particle 1, during its journey, meets a magnet that deflects it upward, the particle 2, instead of continuing its trajectory in a straight line, deflects its direction at the same time, assuming a motion contrary to that of the particle 1.
  • 35. This experiment demonstrates that: 1. the particles are able to communicate each other by transmitting and processing information. 2. the communication is instantaneous.
  • 36. The physicist Niels Bohr said: "Between two [related] particles that turn away from one another in space, there is a form of action - permanent communication. [...] Although two photons were located on two different galaxies they would still continue to remain one entity ..."
  • 37. The experiments of Alain Aspect The experiments of Alain Aspect In 1982, Alain Aspect, with the collaboration of the researchers J. Dalibard and G. Roger of the Optic Institute of the University of Paris, demonstrated the existence of the entanglement, thus confirming the hypothesis of "non – locality” of the quantum theory. The figure shows a simplified scheme of the equipment used by Aspect and his collaborators during the experiments. An excited atom of calcium, at the center of the figure, produces a pair of entangled photons that move along opposite paths “A and B”:
  • 38. Along the path "A“, a birefringent crystal, that acts as a filter, is inserted from time to time. When the photon interacts with the crystal, it can be deflected, with a probability of 50%, or it can cross the crystal, continuing undisturbed on its way. At the end of each path a photon detector is placed that allows the detection of the photons. The amazing thing that Aspect observed was that: when, along the path A, the birefringent crystal was inserted and a deviation of the photon 1 occurred to the detector C, on the path B, also the photon 2 (photon separate and without "obstacles" in front) deflected "spontaneously" and “instantly” toward the detector D. Basically, the act of introducing the birefringent crystal, with the consequent deviation of the photon 1, made instantly and remotely deflect the photon 2. This might sound strange, but that's what actually happens when experiments on pairs of entangled particles are made. So the idea that entangled particles, located in distant places, represent separate entities, must be abandoned.
  • 39. In reference to the uniqueness of the matter that stems from the “non localist” vision of quantum theory, Brian Josephson (the Nobel Prize for Physics) says: "The universe is not a collection of objects, but an inseparable network of vibrating energy patterns in which no single component has independent reality: including the observer".
  • 40. SCHEMATIC REPRESENTATION OF A QUANTUM TELEPORTATION PROCESS Transmitted photon C Transmitting station T A C B A C Photon to be transmitted Entangled photons Receiving station R B Source of entangled photons: Source of entangled photons: Source EPR Source EPR Entanglement is frequently called “EPR effect" from the initials of Albert Einstein, Boris Podolski and Nathan Rosen. They, in 1935, analyzed the consequences of particles placed at great distances. The involved particles are called "EPR pairs”.
  • 41. SHORT DESCRIPTION SHORT DESCRIPTION OF THE QUANTUM TELEPORTATION PROCESS OF THE QUANTUM TELEPORTATION PROCESS 1. Production of a pair of entangled photons A e B by an appropriate device. 2. Sending of the entangled photons A e B respectively to the transmitting station T and to the receiving station R. 3. Sending of the photon C, of which you want to teleport the state of polarization, to the transmitting station T. 4. Interaction, at the start station T, between the photons A and C and measure on the combined system.
  • 42. 5. Simultaneous change, during the measurement, of the polarization state of the photon B, at the R station. 6. Communication to the R station, by the traditional media (e.g.: telephone call), of the result of the measurement on the photon A and the photon C (4 results are possible). 7. Change of the status of photon B based on the information communicated. RESULT Quantum teleportation of the photon C, this means that a photon with the same polarization state of the photon C has been obtained without any measurement on it.
  • 43. More detailed description of the Quantum Teleportation More detailed description of the Quantum Teleportation process process Amanda and Bert intend to teleport the photon C. Amanda is at the T station and Bert is at the R station. At the beginning each receives one photon of an entangled pair: Amanda receives the photon A and Bert receives the photon B. Instead of carrying out a measure on the photons, they keep their photon without disturbing the entangled state. Amanda receives a third photon C that she wants to teleport to Bert. Amanda in practice, without knowing the polarization state of the photon C, wants that Bert has a photon with the same polarization of the photon C. It is important to notice that Amanda cannot simply measure the polarization state of the photon C, and then communicate the result to Bert because, for the uncertainty principle, the measure couldn't accurately reproduce the original state of the photon. To teleport the photon C, Amanda makes A and C to interact and performs a measurement on the system, without determining, in absolute terms, the individual polarizations of the two photons. The measurement can give 1 of 4 possible results.
  • 44. In technical terms, a joint measurement of this type is called “Bell's state measurement” and it has a particular effect: It induces instantly a change in Bert's photon, correlating it to the result of the measurement performed by Amanda and to the state that the photon C originally had. To complete the teleportation, Amanda has to send a message to Bert by the conventional methods (a phone call or a written note). After receiving this message, Bert, if necessary, may transform his photon B in order to make an exact replica of the original photon C. The transformation that Bert should apply depends on the result of the measurement of Amanda. Which of the four possible results Amanda gets, is due to chance. Therefore, Bert does not know how to modify his photon until he receives from Amanda the result of the measurement. After this transformation Bert's photon is in the same state of the photon C.
  • 45. Then, what has been transported is not the photon but its polarization state or, generally, its quantum state. However, since quantum state is a peculiar characteristic of a particle, we can say that to teleport a quantum state is like teleport the particle. It's important to observe that: the measurement that Amanda made, connects the photon A to the photon C. So the photon C loses all the "memory" of its original state. Therefore, the original state of the C photon, after the measurement, disappears from the place where Amanda is. The result of the measurement of Amanda, being totally random, doesn't say anything about the quantum state. In this way, the process bypasses the Heisenberg’s principle which doesn't allow full determination of the state of a particle but allows the teleport of the state, provided that Amanda doesn't try to know what it is. The state of the C photon has been transferred without Amanda and Bert had any knowledge of it.
  • 46. In addition, the teleported quantum information doesn't travel physically. What is transferred, essentially, is just the message on the result of the measurement of Amanda that says to Bert how he has to modify his photon, without any indication on the state of the C photon. In one of the four cases, the measurement of Amanda is lucky and Bert's photon becomes immediately a replica of the original. In this case, it might seem that the information travels instantly from Amanda to Bert, breaking the limit imposed by Einstein. It is not so, in fact Bert has no way of knowing that his photon is already a replica of the original. Only when he learns the result of the measurement of the Bell's state, performed by Amanda and transmitted to him by the classical information, he can take advantage of the information about the teleported quantum state.
  • 47. CONCLUSIONS CONCLUSIONS We are still far from the teleportation of a large object. The main problems are: two entangled objects of the same type are required; the object that should be teleported and the entangled objects must be sufficiently isolated from the environment. If any information is exchanged with the environment, through accidental interaction, the quantum state of the object degrades in a process called "decoherence". It is hard to imagine how you can achieve this absolute isolation for a body of macroscopic dimensions and even more for a human being because he breathes air and exchanges heat with the outside world. But who can predict the future developments? Of course we could use existing technology in order to teleport elementary states, such as those of the photons over distances of few kilometers, and perhaps even up to the satellites. The technology that can teleport states of individual atoms has been reached, as shown by the group led by Serge Haroche of the Ecole Normale Supérieure in Paris, which has produced entangled atoms. Entangled molecules and their teleportation can be reasonably expected within the next decade. What will happen afterwards, nobody knows. What will happen afterwards, nobody knows. back to the table of contents
  • 48. Quantum Teleportation from 1997 to today Quantum Teleportation from 1997 to today The first quantum teleportation experiments were carried out between 1993 and 1997, by two international research groups, led respectively by Francesco De Martini from La Sapienza University in Rome and Anton Zeilinger from the Institute of Experimental Physics in Vienna. They were able to teleport the quantum state of a photon. In 2004: De Martini carried out a teleportation of photons from one part to another of the Danube covering a distance of 600 meters. two groups of scientists, one from the National Institute of Standards and Technology in the United States and one from the University of Innsbruck in Austria, were able to teleport some of the properties of atoms for the first time. The Americans worked with beryllium atoms while the Austrians with calcium atoms.
  • 49. In 2006: some researchers from Niels Bohr Institute in Copenhagen teleported a collective state from a group of about a trillion of atoms to another. The Teleportation applied to the atoms, i.e. to the matter, is a very delicate process compared to that made on the photons, due to the process of decoherence. This process, due to interactions with the environment, destroys the quantum effects, including entanglement. In 2010: in China, the researchers of the Hefei National Laboratory for Physical Sciences reached 16km in the teleportation of photons without the support of optical fibers.
  • 50. In 2012: a group of researchers succeeded in realizing the quantum teleportation of the information relating to a complicated system of about 100 million of rubidium atoms that had a magnitude of about one millimeter. The study was conducted by Jian-Wei Pan of the Hefei National Laboratory for Physical Sciences at the Microscale, with the collaboration of the researchers of the University of Science and Technology in China and of the University of Heidelberg. For the teleportation, scientists prepared in laboratory an entangled pair of granules of rubidium. Entangled granules were placed at the distance of about half a meter and then the two systems were connected by an optical fiber, 150 meters long and rolled up on itself. Before performing the process of quantum teleportation, the scientists mapped the state of excitation of the rubidium atoms in a photon that traveled along the optical fiber. It was possible to realize the teleportation by the interaction between the photon "messenger" with another photon and with the second system of atoms.
  • 51. In 2012: The team of researchers from the University of Science and Technology of China in Shanghai, was able to teleport more than 1100 photons in 4 hours covering a distance of 97km of free space, establishing a new record and overcoming the distance of 16km obtained from the previous experiment in 2010. The research team of the Optical Ground Station of the European Space Agency (ESA) in the Canary Islands settled down a new world record on the distance about the quantum teleportation, reproducing the characteristics of a light particle to a distance of 143km (between Jacobus Kapteyn Telescope La Palma and ESA's Tenerife Train optical).
  • 52. In 2013: A group of physicists from the research center Quantop at the Niels Bohr Institute of the University of Copenhagen has teleported informations between two clouds of gas atoms of cesium far from each other half a meter. The physicists have used two glass containers that were not connected and the teleportation of the information from one cloud to another occurred by means of laser light.
  • 53. It is expected that the next teleportation experiment will consist of a Quantum Teleportation between the Earth and a Satellite in Earth orbit.
  • 54. Applications of the Quantum Teleportation Realization of quantum computers and networks Realization of quantum computers and networks extremely powerful and faster than the actual extremely powerful and faster than the actual classical computers and networks. classical computers and networks. Exchange of information 100% secure. Exchange of information 100% secure. In fact: between the sending station and the receiving In fact: between the sending station and the receiving station only one classic signal is exchanged, this doesn't station only one classic signal is exchanged, this doesn't allow to a person, who intercepts the classic signal, to allow to a person, who intercepts the classic signal, to know the information, in the form of quantum state, that know the information, in the form of quantum state, that you are teleporting. you are teleporting. Dream of teleportation as in "Star Trek" Dream of teleportation as in "Star Trek" back to the introduction
  • 55. QUBITS AND QUANTUM COMPUTERS QUBITS AND QUANTUM COMPUTERS BIT (binary digit) is the unit of classical information. QUBIT or quantum bit (quantum binary digit) is the unit of quantum information.
  • 56. The "classical bits" operate on binary code and can encode only one value at a time: 0 or 1. The "qubits" process the information following the laws of quantum mechanics and the principle of quantum superposition, i.e. the idea that an object can exist in multiple states at the same time; they can take at the same time the state 0 and 1.
  • 57. In a classical system one bit of information can be represented, for example, by the voltage applied to the plates of a capacitor: the charged capacitor denotes the bit 1 and the not charged capacitor denotes the bit 0. Quantistically, one bit of information can be encoded using a twolevel system, such as: the spin states of an electron, the two polarizations of the light.
  • 58. What is a quantum computer? What is a quantum computer? The conditions for the realization of quantum computers and quantum networks, able to offer the best performance in power and speed of calculation, are provided by the QUANTUM TELEPORTATION the phenomenon of teleportation of qubits, achieved by the quantum phenomenon of entanglement.
  • 59. In a quantum computer the information would be recorded in qubits instead of stored in bits as in a classical computer.
  • 60. How much information can be contained in a QUBIT? In practice a Qubit cannot contain more information than a classical bit, because it assumes the value 0 or 1 when the information is processed. Therefore a quantum computer does not have advantages compared to the classical computer, at least for what concerns the amount of information stored. The advantage of a quantum computer instead consists of an exponential increase in computing capability.
  • 61. A quantum processor that can operate on N Qubits, has the computing power of a classical processor that operates on 2N bits. Quantum computers are able to manage, in a few minutes, lots of data
  • 62. TECHNOLOGICAL DIFFICULTIES There are many technological difficulties to be overcome to realize a quantum computer. One of these is the decoherence In other words, the inevitable interaction with the external environment would destroy, in a short time, the quantum coherence, that is the information contained in the quantum computer. At the present, several proposals are under consideration to build a quantum computer (nuclear magnetic resonance, ion traps, optical systems, superconducting circuits, etc.), but currently it is not clear which way is the most likely to succeed.
  • 63. Learn more about: The roots of entanglement http://www.scienzaeconoscenza.it/articolo/le-radici-dell-039entanglement.php The quantum non-separability http://www.scienzaeconoscenza.it/articolo/la-non-separabilitaquantistica.php Quantum bits and Quantum Computers http://phys.org/tags/quantum+bits/ http://phys.org/tags/quantum+computing/  European Space Agency (ESA) http://www.esa.int/esasearch?q=quantum+teleportation back to the introduction