VIEWS: 19 PAGES: 16 CATEGORY: Education POSTED ON: 1/8/2012
Quantum computing Quantum computing is the area of study focused on developing computer technology based on the principles of quantum theory, which explains the nature and behavior of energy and matter on the quantum (atomic and subatomic) level. Development of a quantum computer, if practical, would mark a leap forward in computing capability far greater than that from the abacus to a modern day supercomputer, with performance gains in the billion-fold realm and beyond. The quantum computer, following the laws of quantum physics, would gain enormous processing power through the ability to be in multiple states, and to perform tasks using all possible permutations simultaneously. Current centers of research in quantum computing include MIT, IBM, Oxford University, and the Los Alamos National Laboratory. The essential elements of quantum computing originated with Paul Benioff, working at Argonne National Labs, in 1981. He theorized a classical computer operating with some quantum mechanical principles. But it is generally accepted that David Deutsch of Oxford University provided the critical impetus for quantum computing research. In 1984, he was at a computation theory conference and began to wonder about the possibility of designing a computer that was based exclusively on quantum rules, then published his breakthrough paper a few months later. With this, the race began to exploit his ideas. However, before we delve into what he started, it is beneficial to have a look at the background of the quantum world. Quantum Quantum is the Latin word for amount and, in modern understanding, means the smallest possible discrete unit of any physical property, such as energy or matter . Quantum came into the latter usage in 1900, when the physicist Max Planck used it in a presentation to the German Physical Society. Planck had sought to discover the reason that radiation from a glowing body changes in color from red, to orange, and, finally, to blue as its temperature rises. He found that by making the assumption that radiation existed in discrete units in the same way that matter does, rather than just as a constant electromagnetic wave, as had been formerly assumed, and was therefore quantifiable, he could find the answer to his question. Planck wrote a mathematical equation involving a figure to represent individual units of energy. He called the units quanta . Planck assumed there was a theory yet to emerge from the discovery of quanta, but in fact, their very existence defined a completely new and fundamental law of nature. Einstein's theory of relativity and quantum theory , together, explain the nature and behavior of all matter and energy on earth and form the basis for modern physics. However, conflicts remain between the two. For much of his life, Einstein sought what he called a unified field theory -- one would reconcile the theories' incompatibilities. Subsequently, Superstring Theory and M-theory have been proposed as candidates to fill that role. Quantum is sometimes used loosely, in an adjectival form, to mean on such an infinitessimal level as to be infinite, as, for example, you might say "Waiting for pages to load is quantumly boring." Quantum Theory Quantum theory's development began in 1900 with a presentation by Max Planck to the German Physical Society, in which he introduced the idea that energy exists in individual units (which he called "quanta"), as does matter. Further developments by a number of scientists over the following thirty years led to the modern understanding of quantum theory. The Essential Elements of Quantum Theory: Energy, like matter, consists of discrete units, rather than solely as a continuous wave. Elementary particles of both energy and matter, depending on the conditions, may behave like either particles or waves. The movement of elementary particles is inherently random, and, thus, unpredictable. The simultaneous measurement of two complementary values, such as the position and momentum of an elementary particle, is inescapably flawed; the more precisely one value is measured, the more flawed will be the measurement of the other value. Further Developments of Quantum Theory Niels Bohr proposed the Copenhagen interpretation of quantum theory, which asserts that a particle is whatever it is measured to be (for example, a wave or a particle) but that it cannot be assumed to have specific properties, or even to exist, until it is measured. In short, Bohr was saying that objective reality does not exist. This translates to a principle called superposition that claims that while we do not know what the state of any object is, it is actually in all possible states simultaneously, as long as we don't look to check. To illustrate this theory, we can use the famous and somewhat cruel analogy of Schrodinger's Cat. First, we have a living cat and place it in a thick lead box. At this stage, there is no question that the cat is alive. We then throw in a vial of cyanide and seal the box. We do not know if the cat is alive or if it has broken the cyanide capsule and died. Since we do not know, the cat is both dead and alive, according to quantum law - in a superposition of states. It is only when we break open the box and see what condition the cat is in that the superposition is lost, and the cat must be either alive or dead. The second interpretation of quantum theory is the multiverse or many-worlds theory. It holds that as soon as a potential exists for any object to be in any state, the universe of that object transmutes into a series of parallel universes equal to the number of possible states in which that the object can exist, with each universe containing a unique single possible state of that object. Furthermore, there is a mechanism for interaction between these universes that somehow permits all states to be accessible in some way and for all possible states to be affected in some manner. Stephen Hawking and the late Richard Feynman are among the scientists who have expressed a preference for the many-worlds theory. Which ever argument one chooses, the principle that, in some way, one particle can exist in numerous states opens up profound implications for computing. A Comparison of Classical and Quantum Computing Classical computing relies, at its ultimate level, on principles expressed by Boolean algebra, operating with a (usually) 7-mode logic gate principle, though it is possible to exist with only three modes (which are AND, NOT, and COPY). Data must be processed in an exclusive binary state at any point in time - that is, either 0 (off / false) or 1 (on / true). These values are binary digits, or bits. The millions of transistors and capacitors at the heart of computers can only be in one state at any point. While the time that the each transistor or capacitor need be either in 0 or 1 before switching states is now measurable in billionths of a second, there is still a limit as to how quickly these devices can be made to switch state. As we progress to smaller and faster circuits, we begin to reach the physical limits of materials and the threshold for classical laws of physics to apply. Beyond this, the quantum world takes over, which opens a potential as great as the challenges that are presented. The Quantum computer, by contrast, can work with a two-mode logic gate: XOR and a mode we'll call QO1 (the ability to change 0 into a superposition of 0 and 1, a logic gate which cannot exist in classical computing). In a quantum computer, a number of elemental particles such as electrons or photons can be used (in practice, success has also been achieved with ions), with either their charge or polarization acting as a representation of 0 and/or 1. Each of these particles is known as a quantum bit, or qubit, the nature and behavior of these particles form the basis of quantum computing. The two most relevant aspects of quantum physics are the principles of superposition and entanglement . Superposition Think of a qubit as an electron in a magnetic field. The electron's spin may be either in alignment with the field, which is known as a spin-up state, or opposite to the field, which is known as a spin-down state. Changing the electron's spin from one state to another is achieved by using a pulse of energy, such as from a laser - let's say that we use 1 unit of laser energy. But what if we only use half a unit of laser energy and completely isolate the particle from all external influences? According to quantum law, the particle then enters a superposition of states, in which it behaves as if it were in both states simultaneously. Each qubit utilized could take a superposition of both 0 and 1. Thus, the number of computations that a quantum computer could undertake is 2^n, where n is the number of qubits used. A quantum computer comprised of 500 qubits would have a potential to do 2^500 calculations in a single step. This is an awesome number - 2^500 is infinitely more atoms than there are in the known universe (this is true parallel processing - classical computers today, even so called parallel processors, still only truly do one thing at a time: there are just two or more of them doing it). But how will these particles interact with each other? They would do so via quantum entanglement. Entanglement Particles (such as photons, electrons, or qubits) that have interacted at some point retain a type of connection and can be entangled with each other in pairs, in a process known as correlation . Knowing the spin state of one entangled particle - up or down - allows one to know that the spin of its mate is in the opposite direction. Even more amazing is the knowledge that, due to the phenomenon of superpostition, the measured particle has no single spin direction before being measured, but is simultaneously in both a spin-up and spin-down state. The spin state of the particle being measured is decided at the time of measurement and communicated to the correlated particle, which simultaneously assumes the opposite spin direction to that of the measured particle. This is a real phenomenon (Einstein called it "spooky action at a distance"), the mechanism of which cannot, as yet, be explained by any theory - it simply must be taken as given. Quantum entanglement allows qubits that are separated by incredible distances to interact with each other instantaneously (not limited to the speed of light). No matter how great the distance between the correlated particles, they will remain entangled as long as they are isolated. Taken together, quantum superposition and entanglement create an enormously enhanced computing power. Where a 2-bit register in an ordinary computer can store only one of four binary configurations (00, 01, 10, or 11) at any given time, a 2-qubit register in a quantum computer can store all four numbers simultaneously, because each qubit represents two values. If more qubits are added, the increased capacity is expanded exponentially. Quantum Programming Perhaps even more intriguing than the sheer power of quantum computing is the ability that it offers to write programs in a completely new way. For example, a quantum computer could incorporate a programming sequence that would be along the lines of "take all the superpositions of all the prior computations" - something which is meaningless with a classical computer - which would permit extremely fast ways of solving certain mathematical problems, such as factorization of large numbers, one example of which we discuss below. There have been two notable successes thus far with quantum programming. The first occurred in 1994 by Peter Shor, (now at AT&T Labs) who developed a quantum algorithm that could efficiently factorize large numbers. It centers on a system that uses number theory to estimate the periodicity of a large number sequence. The other major breakthrough happened with Lov Grover of Bell Labs in 1996, with a very fast algorithm that is proven to be the fastest possible for searching through unstructured databases. The algorithm is so efficient that it requires only, on average, roughly N square root (where N is the total number of elements) searches to find the desired result, as opposed to a search in classical computing, which on average needs N/2 searches. The Problems - And Some Solutions The above sounds promising, but there are tremendous obstacles still to be overcome. Some of the problems with quantum computing are as follows: Interference - During the computation phase of a quantum calculation, the slightest disturbance in a quantum system (say a stray photon or wave of EM radiation) causes the quantum computation to collapse, a process known as de-coherence. A quantum computer must be totally isolated from all external interference during the computation phase. Some success has been achieved with the use of qubits in intense magnetic fields, with the use of ions. Error correction - Because truly isolating a quantum system has proven so difficult, error correction systems for quantum computations have been developed. Qubits are not digital bits of data, thus they cannot use conventional (and very effective) error correction, such as the triple redundant method. Given the nature of quantum computing, error correction is ultra critical - even a single error in a calculation can cause the validity of the entire computation to collapse. There has been considerable progress in this area, with an error correction algorithm developed that utilizes 9 qubits (1 computational and 8 correctional). More recently, there was a breakthrough by IBM that makes do with a total of 5 qubits (1 computational and 4 correctional). Output observance - Closely related to the above two, retrieving output data after a quantum calculation is complete risks corrupting the data. In an example of a quantum computer with 500 qubits, we have a 1 in 2^500 chance of observing the right output if we quantify the output. Thus, what is needed is a method to ensure that, as soon as all calculations are made and the act of observation takes place, the observed value will correspond to the correct answer. How can this be done? It has been achieved by Grover with his database search algorithm, that relies on the special "wave" shape of the probability curve inherent in quantum computers, that ensures, once all calculations are done, the act of measurement will see the quantum state decohere into the correct answer. Even though there are many problems to overcome, the breakthroughs in the last 15 years, and especially in the last 3, have made some form of practical quantum computing not unfeasible, but there is much debate as to whether this is less than a decade away or a hundred years into the future. However, the potential that this technology offers is attracting tremendous interest from both the government and the private sector. Military applications include the ability to break encryptions keys via brute force searches, while civilian applications range from DNA modeling to complex material science analysis. It is this potential that is rapidly breaking down the barriers to this technology, but whether all barriers can be broken, and when, is very much an open question. Quantum computing First proposed in the 1970s, quantum computing relies on quantum physics by taking advantage of certain quantum physics properties of atoms or nuclei that allow them to work together as quantum bits, or qubits, to be the computer's processor and memory. By interacting with each other while being isolated from the external environment, qubits can perform certain calculations exponentially faster than conventional computers. Qubits do not rely on the traditional binary nature of computing. While traditional computers encode information into bits using binary numbers, either a 0 or 1, and can only do calculations on one set of numbers at once, quantum computers encode information as a series of quantum- mechanical states such as spin directions of electrons or polarization orientations of a photon that might represent a 1 or a 0, might represent a combination of the two or might represent a number expressing that the state of the qubit is somewhere between 1 and 0, or a superposition of many different numbers at once. A quantum computer can do an arbitrary reversible classical computation on all the numbers simultaneously, which a binary system cannot do, and also has some ability to produce interference between various different numbers. By doing a computation on many different numbers at once, then interfering the results to get a single answer, a quantum computer has the potential to be much more powerful than a classical computer of the same size. In using only a single processing unit, a quantum computer can naturally perform myriad operations in parallel. Quantum computing is not well suited for tasks such as word processing and email, but it is ideal for tasks such as cryptography and modeling and indexing very large databases. Quantum computing - a whole new concept in parallelism! What is quantum computing? It's something that could have been thought up a long time ago - an idea whose time has come. For any physical theory one can ask: what sort of machines will do useful computation? or, what sort of processes will count as useful computational acts? Alan Turing thought about this in 1936 with regard (implicitly) to classical mechanics, and gave the world the paradigm classical computer: the Turing machine. But even in 1936 classical mechanics was known to be false. Work is now under way - mostly theoretical, but tentatively, hesitantly groping towards the practical - in seeing what quantum mechanics means for computers and computing. In a trivial sense, everything is a quantum computer. (A pebble is a quantum computer for calculating the constant-position function - you get the idea.) And of course, today's computers exploit quantum effects (like electrons tunneling through barriers) to help do the right thing and do it fast. For that matter, both the computer and the pebble exploit a quantum effect - the "Pauli exclusion principle", which holds up ordinary matter against collapse by bringing about the kind of degeneracy we call chemistry - just to remain stable solid objects. But quantum computing is much more than that. The most exciting really new feature of quantum computing is quantum parallelism. A quantum system is in general not in one "classical state", but in a "quantum state" consisting (crudely speaking) of a superposition of many classical or classical-like states. This superposition is not just a figure of speech, covering up our ignorance of which classical-like state it's "really" in. If that was all the superposition meant, you could drop all but one of the classical-like states (maybe only later, after you deduced retrospectively which one was "the right one") and still get the time evolution right. But actually you need the whole superposition to get the time evolution right. The system really is in some sense in all the classical-like states at once! If the superposition can be protected from unwanted entanglement with its environment (known as decoherence), a quantum computer can output results dependent on details of all its classical-like states. This is quantum parallelism - parallelism on a serial machine. And if that wasn't enough, machines that would already, in architectural terms, qualify as parallel can benefit from quantum parallelism too - at which point the mind begins to seriously boggle! What is Quantum Computing? Quantum computing is a new method of computing with a hypothetical computer, capable of processing speeds impossible by traditional computers. Though the earliest quantum computers have been built, when practical quantum computing machines hit the market, they will revolutionize an entire industry. However, significant progress must be made before quantum computers have a mainstream use. Quantum computing works by being able to make multiple calculations at one time. Traditional computing works by only making one calculation at a time. While traditional machines do these calculations at an impressive speed, only doing one at a time does limit their capabilities. Quantum computers have no such limitations and can do multiple calculations as fast or faster than traditional computers. Though this may not sound like a major advancement, the ability to make multiple calculations at once can make a big difference in quantum computing. In fact, quantum computers could make today's supercomputers look like children's toys. In fact, quantum computing has the potential to make computers using its technology millions of times more powerful than today's most powerful computers. The key to quantum computing is the qubit. Qubits are different than traditional bits, which can only hold a value of 0 or 1, commonly known as binary to computer users. Instead of being one or the other, qubits can hold a value of both 0 and 1, as well as all values between 0 and 1. Qubits are very small properties, being made of atoms, ions, photons or electrons Is There a Quantum Computer in Your Future? The overriding imperative of computing is "go faster, get smaller". The number of transistors that can be manufactured on a standard silicon wafer has doubled roughly every two years, as Moore's Law predicts. That means transistors keep growing smaller. The smaller the distance between transistors, the faster computations happen. If Moore's Law continues to be an accurate predictor, then around 2020 or 2030 we should see transistors the size of individual atoms. That's when quantum computing will come to fruition. Quantum computing is based upon physics completely different from that observed in the electronic devices of today. In today's computing paradigm, a transistor can be in only one of two states called bits - 0 or 1, on or off. But in the realm of quantum computing a transistor can be in a state of 0, 1, or a "superposition" of 0 or 1. And there can be many superpositions. These quantum bits are called "qubits." Physically, qubits are encoded in atoms, photons, ions, or electrons. Whereas a standard transistor can perform only one operation at a time, a qubit can perform many simultaneously. Therefore a quantum computer containing the same number of transistors as an ordinary computer of today can be a million times faster. A 30-qubit quantum computer could perform as many as 10 teraflops - 10 trillion floating-point operations per second! Today's desktop computers perform gigaflops - billions of operations per second. So obviously, that's where the interest in quantum computing comes from - speed. A personal computer a million times faster than the one currently on your desk boggles the mind. After all, how fast can you type? But there are applications that would benefit from that type of speed, such as image recognition, cryptography, and other problems that require enormous computing power. Personally, I'd be happy with a computer that's ready to go as soon as you turn it on. I don't anticipate being able to type a million times faster than I already do. J One problem with quantum computing is that if you observe the quantum state of a qubit, it changes. So scientists must devise an indirect method of determining the state of a qubit. To do this, they are trying to take advantage of another quantum property called "entanglement." At the quantum level, if you apply a force to two particles they become "entangled;" a change in the state of one particle is instantly reflected in the other particle's change to the opposite state. So by observing the state of the second particle, physicists hope to determine the state of the first. Yes, quantum mechanics is rather confusing. But from a layman's perspective, it's enough to know that quantum computing is based on a new type of transistor that is represented by the changing states of atomic particles. And the promise of quantum computing is a HUGE breakthrough in speed. Are Quantum Computers Available Today? There is at least one firm that claims to have created a rudimentary, working quantum computer. Canada-based D-Wave Systems has demonstrated a 16-qubit quantum computer that solved sudoku puzzles and other pattern-matching problems. Some in the scientific community are skeptical about D-Wave's claims, but there is definite progress on the quantum computing front every day. Quantum computers need at least a few dozen qubits in order to solve real-world problems usefully. It may be several years, even a couple of decades, before a practical quantum computer is put into production. But just as world records fell more rapidly after the first sub-four-minute mile was run, the breakthrough of the first commercial quantum computer will undoubtedly be followed by very rapid increases in quantum computing capabilities; reductions in costs; and shrinkage in size. In a decade or so, we can expect to find old-school transistors and simple on- off bit technology joining analog video tape in the dustbin of technology history. Molecular electronics involves the study and application of molecular building blocks for the fabrication of electronic components. This includes both bulk applications of conductive polymers, and single-molecule electronic components for nanotechnology. Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity.[1] Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers is their processability, mainly by dispersion. Conductive polymers are generally not plastics, i.e., they are not thermoformable. But, like insulating polymers, they are organic materials. They can offer high electrical conductivity but do not show mechanical properties as other commercially used polymers do. The electrical properties can be fine-tuned using the methods of organic synthesis [2] and by advanced dispersion techniques A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalent chemical bonds. Although the term polymer is sometimes taken to refer to plastics, it actually encompasses a large class of natural and synthetic materials with a wide variety of properties. Because of the extraordinary range of properties of polymeric materials, [2] they play an essential and ubiquitous role in everyday life.[3] This role ranges from familiar synthetic plastics and elastomers to natural biopolymers such as nucleic acids and proteins that are essential for life. A dispersion is a system in which particles are dispersed in a continuous phase of a different composition (or state). See also emulsion. A dispersion is classified in a number of different ways, including how large the particles are in relation to the particles of the continuous phase, whether or not precipitation occurs, and the presence of Brownian motion. There are three main types of dispersions: Suspension Colloid Solution Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has developed into one of the most important branches of organic chemistry. There are two main areas of research fields within the general area of organic synthesis: total synthesis and methodology. Methodology can be: 1. "the analysis of the principles of methods, rules, and postulates employed by a discipline"; [1] 2. "the systematic study of methods that are, can be, or have been applied within a discipline". [1] 3. A documented process for management of projects that contains procedures, definitions and explanations of techniques used to collect, store, analyze and present information as part of a research process in a given discipline. 4. the study or description of methods [2] In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions. In modern laboratory usage, this tends to imply that the process is reproducible, reliable, and established to work in multiple laboratories. An interdisciplinary pursuit, molecular electronics spans physics, chemistry, and materials science. The unifying feature is the use of molecular building blocks for the fabrication of electronic components. This includes both passive (e.g. resistive wires) and active components such as transistors and molecular-scale switches. Due to the prospect of size reduction in electronics offered by molecular-level control of properties, molecular electronics has aroused much excitement both in science fiction and among scientists. Molecular electronics provides means to extend Moore's Law beyond the foreseen limits of small-scale conventional silicon integrated circuits. Molecular electronics is split into two related but separate subdisciplines: molecular materials for electronics utilizes the properties of the molecules to affect the bulk properties of a material, while molecular scale electronics focuses on single-molecule applications Molecular scale electronics Molecular scale electronics, also called single molecule electronics, is a branch of nanotechnology that uses single molecules, or nanoscale collections of single molecules, as electronic components. Because single molecules constitute the smallest stable structures imaginable this miniaturization is the ultimate goal for shrinking electrical circuits. Conventional electronics have traditionally been made from bulk materials. With the bulk approach having inherent limitations in addition to becoming increasingly demanding and expensive, the idea was born that the components could instead be built up atom for atom in a chemistry lab (bottom up) as opposed to carving them out of bulk material (top down). In single molecule electronics, the bulk material is replaced by single molecules. That is, instead of creating structures by removing or applying material after a pattern scaffold, the atoms are put together in a chemistry lab. The molecules utilized have properties that resemble traditional electronic components such as a wire, transistor or rectifier. Single molecule electronics is an emerging field, and entire electronic circuits consisting exclusively of molecular sized compounds are still very far from being realized. However, the continuous demand for more computing power together with the inherent limitations of the present day lithographic methods make the transition seem unavoidable. Currently, the focus is on discovering molecules with interesting properties and on finding ways to obtaining reliable and reproducible contacts between the molecular components and the bulk material of the electrodes. Molecular electronics operates in the quantum realm of distances less than 100 nanometers. The miniaturization down to single molecules brings the scale down to a regime where quantum effects are important. As opposed to the case in conventional electronic components, where electrons can be filled in or drawn out more or less like a continuous flow of charge, the transfer of a single electron alters the system significantly. The significant amount of energy due to charging has to be taken into account when making calculations about the electronic properties of the setup and is highly sensitive to distances to conducting surfaces nearby. Graphical representation of a rotaxane, useful as a molecular switch. One of the biggest problems with measuring on single molecules is to establish reproducible electrical contact with only one molecule and doing so without shortcutting the electrodes. Because the current photolithographic technology is unable to produce electrode gaps small enough to contact both ends of the molecules tested (in the order of nanometers) alternative strategies is put into use. These include molecular- sized gaps called break junctions, in which a thin electrode is stretched until it breaks. Another method is to use the tip of a scanning tunneling microscope (STM) to contact molecules adhered at the other end to a metal substrate.[3] Another popular way to anchor molecules to the electrodes is to make use of sulfurs’ high affinity to gold; though useful, the anchoring is non-specific and thus anchors the molecules randomly to all gold surfaces, and the contact resistance is highly dependent on the precise atomic geometry around the site of anchoring and thereby inherently compromises the reproducibility of the connection. To circumvent the latter issue, experiments has shown that fullerenes could be a good candidate for use instead of sulfur because of the large conjugated π-system that can electrically contact many more atoms at once than a single atom of sulfur.[4] One of the biggest hindrances for single molecule electronics to be commercially exploited is the lack of techniques to connect a molecular sized circuit to bulk electrodes in a way that gives reproducible results. Also problematic is the fact that some measurements on single molecules are carried out in cryogenic temperatures (close to absolute zero) which is very energy consuming Molecular materials for electronics Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity in their bulk state.[6] Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers is their processability, mainly by dispersion. Conductive polymers are not plastics, i.e., they are not thermoformable, but they are organic polymers, like (insulating) polymers. They can offer high electrical conductivity but do not show mechanical properties as other commercially used polymers do. The electrical properties can be fine-tuned using the methods of organic synthesis [7] and by advanced dispersion techniques.[8] The linear-backbone "polymer blacks" (polyacetylene, polypyrrole, and polyaniline) and their copolymers are the main class of conductive polymers. Historically, these are known as melanins.PPV and its soluble derivatives have emerged as the prototypical electroluminescent semiconducting polymers. Today, poly(3- alkylthiophenes) are the archetypical materials for solar cells and transistors.[7] Conducting polymers have backbones of contiguous sp2 hybridized carbon centers. One valence electron on each center resides in a pz orbital, which is orthogonal to the other three sigma-bonds. The electrons in these delocalized orbitals have high mobility when the material is "doped" by oxidation, which removes some of these delocalized electrons. Thus the conjugated p-orbitals form a one-dimensional electronic band, and the electrons within this band become mobile when it is partially emptied. Despite intensive research, the relationship between morphology, chain structure and conductivity is poorly understood yet. [9] Conductive polymers enjoy few large-scale applications due to their poor processability. They have been known to have promise in antistatic materials[7] and they have been incorporated into commercial displays and batteries, but there have had limitations due to the manufacturing costs, material inconsistencies, toxicity, poor solubility in solvents, and inability to directly melt process. Nevertheless, conducting polymers are rapidly gaining attraction in new applications with increasingly processable materials with better electrical and physical properties and lower costs. With the availability of stable and reproducible dispersions, PEDOT and polyaniline have gained some large scale applications. While PEDOT (poly(3,4- ethylenedioxythiophene)) is mainly used in antistatic applications and as a transparent conductive layer in form of PEDOT:PSS dispersions (PSS=polystyrene sulfonic acid), polyaniline is widely used for printed circuit board manufacturing – in the final finish, for protecting copper from corrosion and preventing its solderability.[8] The new nanostructured forms of conducting polymers particularly, provide fresh air to this field with their higher surface area and better dispersability Quantum mechanics Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of the dual particle-like and wave-like behaviour and interaction of matter and energy. Quantum mechanics departs from classical mechanics primarily at the atomic and sub-atomic scales, the so-called quantum realm. In special cases some quantum mechanical processes are macroscopic, but these emerge only at extremely low or extremely high energies or temperatures. The term was coined by Max Planck, and derives from the observation that some physical quantities can be changed only by discrete amounts, or quanta, as multiples of the Planck constant, rather than being capable of varying continuously or by any arbitrary amount. For example, the angular momentum, or more generally the action, of an electron bound into an atom or molecule is quantized. Although an unbound electron does not exhibit quantized energy levels, one which is bound in an atomic orbital has quantized values of angular momentum. In the context of quantum mechanics, the wave–particle duality of energy and matter and the uncertainty principle provide a unified view of the behavior of photons, electrons and other atomic-scale objects. The mathematical formulations of quantum mechanics are abstract. Similarly, the implications are often counter-intuitive in terms of classical physics. The centerpiece of the mathematical formulation is the wavefunction (defined by Schrödinger's wave equation), which describes the probability amplitude of the position and momentum of a particle. Mathematical manipulations of the wavefunction usually involve the bra-ket notation, which requires an understanding of complex numbers and linear functionals. The wavefunction treats the object as a quantum harmonic oscillator and the mathematics is akin to that of acoustic resonance. Many of the results of quantum mechanics do not have models that are easily visualized in terms of classical mechanics; for instance, the ground state in the quantum mechanical model is a non-zero energy state that is the lowest permitted energy state of a system, rather than a traditional classical system that is thought of as simply being at rest with zero kinetic energy. Fundamentally, it attempts to explain the peculiar behaviour of matter and energy at the subatomic level— an attempt which has produced more accurate results than classical physics in predicting how individual particles behave. But many unexplained anomolies remain. Historically, the earliest versions of quantum mechanics were formulated in the first decade of the 20th Century, around the time that atomic theory and the corpuscular theory of light as interpreted by Einstein first came to be widely accepted as scientific fact; these latter theories can be viewed as quantum theories of matter and electromagnetic radiation. Following Schrödinger's breakthrough in deriving his wave equation in the mid-1920s, quantum theory was significantly reformulated away from the old quantum theory, towards the quantum mechanics of Werner Heisenberg, Max Born, Wolfgang Pauli and their associates, becoming a science of probabilities based upon the Copenhagen interpretation of Niels Bohr. By 1930, the reformulated theory had been further unified and formalized by the work of Paul Dirac and John von Neumann, with a greater emphasis placed on measurement, the statistical nature of our knowledge of reality, and philosophical speculations about the role of the observer. The Copenhagen interpretation quickly became (and remains) the orthodox interpretation. However, due to the absence of conclusive experimental evidence there are also many competing interpretations. Quantum mechanics has since branched out into almost every aspect of physics, and into other disciplines such as quantum chemistry, quantum electronics, quantum optics and quantum information science. Much 19th Century physics has been re-evaluated as the classical limit of quantum mechanics and its more advanced developments in terms of quantum field theory, string theory, and speculative quantum gravity theories. Applications Quantum mechanics had enormous success in explaining many of the features of our world. The individual behaviour of the subatomic particles that make up all forms of matter—electrons, protons, neutrons, photons and others—can often only be satisfactorily described using quantum mechanics. Quantum mechanics has strongly influenced string theory, a candidate for a theory of everything (see reductionism) and the multiverse hypothesis. Quantum mechanics is important for understanding how individual atoms combine covalently to form chemicals or molecules. The application of quantum mechanics to chemistry is known as quantum chemistry. (Relativistic) quantum mechanics can in principle mathematically describe most of chemistry. Quantum mechanics can provide quantitative insight into ionic and covalent bonding processes by explicitly showing which molecules are energetically favorable to which others, and by approximately how much.[40] Most of the calculations performed in computational chemistry rely on quantum mechanics.[41] A working mechanism of a resonant tunneling diode device, based on the phenomenon of quantum tunneling through the potential barriers. Much of modern technology operates at a scale where quantum effects are significant. Examples include the laser, the transistor (and thus the microchip), the electron microscope, and magnetic resonance imaging. The study of semiconductors led to the invention of the diode and the transistor, which are indispensable for modern electronics. Researchers are currently seeking robust methods of directly manipulating quantum states. Efforts are being made to develop quantum cryptography, which will allow guaranteed secure transmission of information. A more distant goal is the development of quantum computers, which are expected to perform certain computational tasks exponentially faster than classical computers. Another active research topic is quantum teleportation, which deals with techniques to transmit quantum information over arbitrary distances. Quantum tunneling is vital in many devices, even in the simple light switch, as otherwise the electrons in the electric current could not penetrate the potential barrier made up of a layer of oxide. Flash memory chips found in USB drives use quantum tunneling to erase their memory cells. Quantum mechanics primarily applies to the atomic regimes of matter and energy, but some systems exhibit quantum mechanical effects on a large scale; superfluidity (the frictionless flow of a liquid at temperatures near absolute zero) is one well-known example. Quantum theory also provides accurate descriptions for many previously unexplained phenomena such as black body radiation and the stability of electron orbitals. It has also given insight into the workings of many different biological systems, including smell receptors and protein structures.[42] Recent work on photosynthesis has provided evidence that quantum correlations play an essential role in this most fundamental process of the plant kingdom.[43] Even so, classical physics often can be a good approximation to results otherwise obtained by quantum physics, typically in circumstances with large numbers of particles or large quantum numbers. (However, some open questions remain in the field of quantum chaos.) Introduction to quantum mechanics Quantum mechanics is the body of scientific principles which tries to explain the behaviour of matter and its interactions with energy on the scale of atoms and atomic particles. Just before 1900, it became clear that classical physics was unable to explain certain phenomena. Coming to terms with these limitations led to the development of quantum mechanics, a major revolution in physics. This article describes how the limitations of classical physics were discovered, and describes the main concepts of the quantum theory which replaced it in the early decades of the 20th Century.[note 1] These concepts are described in roughly the order they were first discovered; for a more complete history of the subject see History of quantum mechanics. Some aspects of quantum mechanics can seem counter-intuitive, because they describe behaviour quite different to that seen at larger length scales, where classical physics is an excellent approximation. In the words of Richard Feynman, quantum mechanics deals with "nature as She is—absurd."[1] Many types of energy, such as photons (discrete units of light), behave in some respects like particles and in other respects like waves. Radiators of photons - such as neon lights - have emission spectra which are discontinuous, in that only certain frequencies of light are present. Quantum mechanics predicts the energies, the colours, and the spectral intensities of all forms of electromagnetic radiation. But quantum mechanics theory ordains that the more closely one pins down one measure (such as the position of a particle), the less precise another measurement pertaining to the same particle (such as its momentum) must become. Put another way, measuring position first and then measuring momentum does not have the same outcome as measuring momentum first and then measuring position; the act of measuring the first property necessarily introduces additional energy into the micro-system being studied, thereby perturbing that system. Even more disconcerting, pairs of particles can be created as entangled twins — which means that a measurement which pins down one property of one of the particles will instantaneously pin down the same or another property of its entangled twin, regardless of the distance separating them — though this may be regarded as merely a mathematical, rather than a real, anomaly. The first quantum theory: Max Planck and black body radiation Hot metalwork from a blacksmith. The yellow-orange glow is the visible part of the thermal radiation emitted due to the high temperature. Everything else in the picture is glowing with thermal radiation as well, but less brightly and at longer wavelengths that the human eye cannot see. A far-infrared camera will show this radiation. Thermal radiation is electromagnetic radiation emitted from the surface of an object due to the object's temperature. If an object is heated sufficiently, it starts to emit light at the red end of the spectrum — it is "red hot". Heating it further causes the colour to change, as light at shorter wavelengths (higher frequencies) begins to be emitted. It turns out that a perfect emitter is also a perfect absorber. When it is cold, such an object looks perfectly black, as it emits practically no visible light, because it absorbs all the light that falls on it. Consequently, an ideal thermal emitter is known as a black body, and the radiation it emits is called black body radiation. In the late 19th century, thermal radiation had been fairly well characterized experimentally. The wavelength at which the radiation is strongest is given by Wien's displacement law, and the overall power emitted per unit area is given by the Stefan–Boltzmann law. So, as temperature increases, the glow colour changes from red to yellow to white to blue. Even as the peak wavelength moves into the ultra-violet, enough radiation continues to be emitted in the blue wavelengths that the body continues to appear blue. It never becomes invisible—indeed, the radiation of visible light increases monotonically with temperature.[2] Physicists were searching for a theoretical explanation for these experimental results. Quantum mechanics is a mathematical theory that can describe the behavior of objects that are roughly 10,000,000,000 times smaller than a typical human being. Quantum particles move from one point to another as if they are waves. However, at a detector they always appear as discrete lumps of matter. There is no counterpart to this behavior in the world that we perceive with our own senses. One cannot rely on every-day experience to form some kind of "intuition" of how these objects move. The intuition or "understanding" formed by the study of basic elements of quantum mechanics is essential to grasp the behavior of more complicated quantum systems. The approach adopted in all textbooks on quantum mechanics is that the mathematical solution of model problems brings insight in the physics of quantum phenomena. The mathematical prerequisites to work through these model problems are considerable. Moreover, only a few of them can actually be solved analytically. Furthermore, the mathematical structure of the solution is often complicated and presents an additional obstacle for building intuition. This presentation introduces the basic concepts and fundamental phenomena of quantum physics through a combination of computer simulation and animation. The primary tool for presenting the simulation results is computer animation. Watching a quantum system evolve in time is a very effective method to get acquainted with the basic features and peculiarities of quantum mechanics. The images used to produce the computer animated movies shown in this presentation are not created by hand but are obtained by visualization of the simulation data. The process of generating the simulation data for the movies requires the use of computers that are far more powerful than Pentium III based PC 's. At the time that these simulations were carried out (1994), most of them required the use of a supercomputer. Consequently, within this presentation, it is not possible to change the model parameters and repeat a simulation in real time. This presentation is intended for all those who are interested to learn about the fundamentals of quantum mechanics. Some knowledge of mathematics will help but is not required to understand the basics. This presentation is not a substitute for a textbook. The presentation begins by showing the simplest examples, such as the motion of a free particle, a particle in an electric field, etc.. Then, the examples become more sophisticated in the sense that one can no longer rely on one's familiarity with classical physics to describe some of the qualitative features seen in the animations. Classical notions are of no use at all for the last set of examples. However, once all other examples have been "understood", it should be possible to "explain" the behavior of these systems also. Instead of using a comprehensive mathematical apparatus to obtain and analyze solutions of model problems, a computer simulation technique is employed to solve these problems including those that would prove intractable otherwise. The introduction of the quantum The Quantum Mechanical era commenced in 1900 when Max Planck postulated that everything is made up of little bits he called quanta (one quantum; two quanta). Matter had its quanta but also the forces that kept material objects together. Forces could only come in little steps at the time; there was no more such a thing as infinitely small. Albert Einstein took matters further when he successfully described how light interacts with electrons but it wasn't until the 1920's that things began to fall together and some fundamental rules about the world of the small where wrought almost by pure thought. The men who mined these rules were the arch beginners of Quantum Mechanics, the Breakfast Club of the modern era. Names like Pauli, Heisenberg, Schrödinger, Born, Rutherford and Bohr still put butterflies in the bellies of those of us who know what incredible work these boys - as most of them where in their twenties; they were rebels, most of them not even taken serious - achieved. They were Europeans, struck by the depression, huddled together on tiny attics peeking into a strange new world as once the twelve spies checked out the Promised Land. Let all due kudoes abound. Believing the unbelievable One of the toughest obstacles the early Quantum Mechanics explorers had to overcome was their own beliefs in determinism. Because the world of the small is so different, people had to virtually reformat the system of logic that had brought them thus far. In order to understand nature they had to let go of their intuition and embrace a completely new way of thinking. The things they discovered where fundamental rules that just were and couldn't really be explained in terms of the large scale world. Just like water is wet and fire is hot, quantum particles display behavior that are inherent to them alone and can't be compared with any material object we can observe with the naked eye. One of those fundamental rules is that everything is made up from little bits. Material objects are made up of particles, but also the forces that keep those objects together. Light, for instance, is besides that bright stuff which makes things visible, also a force (the so-called electromagnetic force) that keeps electrons tied to the nuclei of atoms, and atoms tied together to make molecules and finally objects. In Scriptures Jesus is often referred to as light, and most exegetes focus on the metaphorical value of these statements. But as we realize that all forms of matter are in fact 2 'solidified' light (energy, as in E=mc ) and the electromagnetic force holds all atoms together, the literal value of Paul's statement "and He is before all things, and in Him all things hold together (Col 1:17)" becomes quite compelling. Particles are either so-called real particles, also known as fermions, or they are force particles, also known as bosons. Quarks, which are fermions, are bound together by gluons, which are bosons. Quarks and gluons form nulceons, and nucleons bound together by gluons form the nuclei of atoms. The electron, which is a fermion, is bound to the nucleus by photons, which are bosons. The whole shebang together forms atoms. Atoms form molecules. Molecules form objects. Everything that we can see, from the most distant stars to the girl next door, or this computer you are staring at and yourself as well are made up from a mere 3 fermions and 9 bosons. The 3 fermions are Up-quark, Down-quark and the electron. The 9 bosons are 8 gluons and 1 photon. Like so: Quanta Atoms Molecules Objects But the 3 fermions that make up our entire universe are not all there is. These 3 are the survivors of a large family of elementary particles and this family is now known as the Standard Model. What happened to the rest? Will they ever be revived? We will learn more about the Standard Model a little further up. First we will take a look at what quantum particles are and in which weird world they live. (If you plan to research these matters more we have written out the most common quantum phrases in a table for your convenience. Have a quick look at it so that you know where to find it in case you decide you need it). Quantum Gates and Circuits Quantum gates would be the building blocks of quantum computers, and they could theoretically calculate much faster than an ordinary computer for certain types of arithmetic problems. Crudely put, the idea is that a quantum system can achieve calculation with the wavefunction in the "wave" mode rather than the "particle" mode. Wave phenomena are inherently "parallel" when used as a computational tool, so you'd be doing lots of "work" in a single computational step. Imagine that you have a computer with a large number in it. You want to divide that number by all the numbers from 1 to 1e100 to find the one that divides into it evenly. In an ordinary computer, you would essentially try each divisor one after the next. A quantum computer could in principle try all the divisors simultaneously. You would make a quantum "measurment" of the result that had no remainder, forcing the one calculation you wanted to see to become the manifested value. It is much like an analog computer that solves a fluid dynamics problem by direct simulation, but in the quantum computing case you still emply the methods of digital computers and gain parallelism from the indeterminacy of the quantum system. Well, this is not really accurate. The biggest difference between a qubit and an ordinary bit is the fact that a bit is either 1 or 0. The qubit is a SUPERPOSITION of 1 and 0. So the qubit really is the 'combination' of the two possible bit-states. The clue in QM-related calculations is the fact that you don't measure one specific qubit because all the information in this massive quantum paralellism would be gone (the superposition is broken). For example, you can 'calculate' a thousand values for any f(x) in just one step. Classically you would need 1000 calculations. Ofcourse you cannot just measure what outcome 926 is ( ie the term on the 926th position in the superposition of |x>|f(x)>). Well, you can but then all other terms are lost and you have no benifits of the QM- approach compared to the classical one. What you can do is try to figure out mutual connections between the different terms in the superposition, like phase-differences or something like that. Further info can be found on John Preskill's webpage, just google for his name;;;Also, look up the problem of Deutsch marlon