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- 1. PRESENTATION ON QUANTUM COMPUTERS FAST EFFICIENTAND POWERFUL MACHINESOF FUTURE BY:- MONIKA 2K10/EP/028
- 2. Lately, the key to improving computer performance has been the reduction of size in the transistors used in modern processors. This continual reduction however, cannot continue for much longer. If the transistors become much smaller, the strange effects of quantum mechanics will begin to hinder their performance. It would therefore seem that these effects present a fundamental limit to our computer technology, or do they?The word "quantum" can conjure up quite a few meanings. It's a reference to quantity. It's SPECTRE reborn for the modern James Bond films. And it just sounds science-y in general thanks to quantum dot displays, quantum mechanics and quantum entanglement. Quantum computing may be the biggest buzzword of them all: it's an exciting and extremely complex technology, and the science community's Top Men have barely scratched the surface of it. A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data.Quantum computers perform operations with qubits (quantum bits) rather than the binary bits of transistor-based computers The computing power of a quantum computer grows exponentially with its size A processor that can use registers of qubits will in effect be able to perform calculations using all the possible values of the input registers simultaneously. This phenomenon is called quantum parallelism, and is the motivating force behind the research being carried out in quantum computing
- 3. QUBITS VS. BITS Let's start with regular bits. They're binary--meaning they represent 1 or 0, on or off--and are used to perform calculations and represent information in computers. Qubits are not binary. Thanks to the principle of quantum superposition, quantum bits are both 0 and 1 simultaneously. Quantum superposition states that a quantum element will only return a result in one state when measured. Here a second principle comes into play: quantum entanglement. Entanglement is actually how we "measure" the interaction of electrons, molecules, photons, and other particles. Not only can a 'quantum bit', usually referred to as a 'qubit', exist in the classical 0 and 1 states, it can also be in a coherent superposition of both. When a qubit is in this state it can be thought of as existing in two universes, as a 0 in one universe and as a 1 in the other. An operation on such a qubit effectively acts on both values at the same time. The significant point being that by performing the single operation on the qubit, we have performed the operation on two different values. Likewise, a two-qubit system would perform the operation on 4 values, and a three-qubit system on eight. Increasing the number of qubits therefore exponentially increases the 'quantum parallelism' we can obtain with the system. With the correct type of algorithm it is possible to use this parallelism to solve certain problems in a fraction of the time taken by a classical computer.
- 4. QUANTUM COMPUTERS COULD ONE DAY REPLACE SILICON CHIPS, JUST LIKE THE TRANSISTOR ONCE REPLACED THE VACUUM TUBE.
- 5. QUANTUM ENTANGLEMENT The quantum entanglement is based on an idea that the tiny particles can be connected with each other in such a way that change in state of one affects the other, even if they happen to be miles apart. quantum computers encode data using this phenomenon Permanently links two objects So that each is affected by the experience of other no matter how far they are Up till now entangled systems involving mainly photons or atomic gases have been observed Called the entangled pair (EPR) : two bits at the price of one….. To achieve the unique feat the researchers made use of high powered magnetic fields and super low temperatures to produce entanglement between the electron and the nucleus of an atom. The atom that was used was of the phosphorous element and it was embedded in a silicon crystal.The entire phenomena is based on the magnet like behavior shown by the nucleus and electrons of an atom.
- 6. QUANTUM CRYPTOGRAPHY The expected capabilities of quantum computation promise great improvements in the world of cryptography. Ironically the same technology also poses current cryptography techniques a world of problems. They will create the ability to break the RSA coding system and this will render almost all current channels of communication insecure
- 7. ADVANTAGES There are several reasons that researchers are working so hard to develop a practical quantum computer. First, atoms change energy states very quickly -- much more quickly than even the fastest computer processors. Next, given the right type of problem, each qubit can take the place of an entire processor -- meaning that 1,000 ions of say, barium, could take the place of a 1,000-processor computer. The key is finding the sort of problem a quantum computer is able to solve. If functional quantum computers can be built, they will be valuable in factoring large numbers, and therefore extremely useful for decoding and encoding secret information. If one were to be built today, no information on the Internet would be safe. Our current methods of encryption are simple compared to the complicated methods possible in quantum computers. Quantum computers could also be used to search large databases in a fraction of the time that it would take a conventional computer. The theories of quantum computation suggest that every physical object, even the universe, is in some sense a quantum computer. As Turing's work says that all computers are functionally equivalent, computers should be able to model every physical process. Ultimately this suggests that computers will be capable of simulating conscious rational thought. And a quantum computer will be the key to achieving true artificial intelligence Quantum communication systems allow a sender and receiver to agree on a code without ever meeting in person. The uncertainty principle, an inescapable property of the quantum world, ensures that if an eavesdropper tries to monitor the signal in transit it will be disturbed in such a way that the sender and receiver are alerted
- 8. DEVELOPMENTS IN THIS FIELD Quantum computing sounds like science fiction -as satellites, moon shots, and the original microprocessor once were. But the age of computing in not even at the end of the beginning. The julish supercomputer can now simulate the largest quantum computer system in the world with 42 bits. Physicists Identify Room Temperature Quantum Bits in Widely Used Semiconductor-The research team at UC Santa Barbara discovered that silicon carbide contains crystal imperfections that can be controlled at a quantum mechanical level First quantum computer- University of Southern California became the first academic institution to house an operational quantum computer system on 28th october 2011. D-Wave One Adiabatic Quantum Computer, the first commercially available quantum computer
- 9. QUANTUM COMPUTERS COULD OVERTURN HEISENBERG’S UNCERTAINTY PRINCIPLE The uncertainty principle is at the foundation of quantum mechanics: You can measure a particle's position or its velocity, but not both. Now it seems that quantum computer memory could let us violate this rule. A physicist Paul Dirac explained that one of the very, very few ways to measure a particle's position is to hit it with a photon and then chart where the photon lands on a detector. That gives you the particle's position, yes, but it's also fundamentally changed its velocity, and the only way to learn that would consequently alter its position
- 10. APPLICATIONS OF QUANTUM COMPUTING Can solve sophisticated algorithms like Shor's algorithm Simulation of quantum mechanical systems - On classical computers, the dynamics of a quantum system can be simulated using approximations. A quantum computer however, can be "programmed" to simulate the behaviour of a system by inducing interactions between its variables. These imitate the characteristics of the system in question. A quantum computer would, for example, allow the "Hubbard Model" (which describes the movement of electrons within a crystal) to be simulated, a task that is beyond the scope of current conventional computers. Quantum Communication Artificial Intelligence Quantum Cryptography Improved Error Correction and Error Detection Through similar processes that support ultra-secure and super-dense communications, the existing bit streams can be made more robust and secure by improvements in error correction and detection. Recovering informational from a noisy transmission path will also be a lucrative and useful practice.
- 11. CHALLENGES AHEAD The first is scalability - how do you build systems with large numbers of qubits The pitfall of quantum computing – decoherence -As soon as it measurable interacts with the environment it will decohere and fall into one of the two classical states. This is the problem of decoherence and is a stumbling block for quantum computers as the potential power of quantum computers depends on the quantum parallelism brought about by the coherent state. This problem is compounded by the fact that even looking at a qubit can cause it to decohere, making the process of obtaining a solution from a quantum computer just as difficult as performing the calculation itself. A recent project from the University of California, Santa Barbara actually built a rudimentary microprocessor using qubits, but it's a far cry from an Intel or AMD chip the quantum computer's qubits only stay in an entangled state for 400 nanoseconds. That's 400 nanoseconds of operation--not exactly long enough to substitute for the computers we use day in and day out. The current challenge is not to build a full quantum computer right away but rather to move from the experiments in which we merely observe quantum phenomena to experiments in which we can control these phenomena. This is a first step towards quantum logic gates and simple quantum networks
- 12. RESEARCHES GOING ON IBM has embarked upon a five year project to try its hand at quantum computing. Researchers in quantum communication have enjoyed a greater level of success. The partial quantum computers involved have enabled secure communication over distances as far as 10km A DARPA Quantum Network became fully operational on Oct 23/03 in BBN’s laboratories, running the world’s first Quantum Key Distribution (QKD) network using 24×7 quantum cryptography to provide unprecedented levels of security for standard Internet traffic flows. Quantum computing is certainly 'on the radar' of IBM, HP, and other supercomputing vendors, but it is difficult to say how many engineers they have working on this technology
- 13. CONCLUSION There's just one catch: it will be years, or even decades, before quantum computers can operate in place of or alongside transistor-based computers. If someone makes a breakthrough in developing a fault-tolerant system with quantum error correction, it might be time to get excited about quantum computing--that will be a Godzilla-sized step along the path that ends in a genuinely usable machine. From a fundamental standpoint, however, it does not matter how useful quantum computation turns out to be, nor does it matter whether we build the first quantum computer tomorrow, next year or centuries from now. Some physicists are pessimistic about the prospects of substantial experimental advances in the field . They believe that decoherence will in practice never be reduced to the point where more than a few consecutive quantum computational steps can be performed. Others, more optimistic researchers, believe that practical quantum computers will appear in a matter of years rather than decades. This may prove to be a wishful thinking but the fact is the optimism, however naive, makes things happen. After all, it used to be a widely accepted "scientific truth" that no machine heavier than air will ever fly. Although the future of quantum computing looks promising, we have only just taken our first steps to actually realizing a quantum computer. There are many hurdles, which need to be overcome before we can begin to appreciate the benefits they may deliver. Researchers around the world are racing to be the first to achieve a practical system, a task, which some scientists think, is futile. David Deutsch - one of the groundbreaking scientists in the world of quantum computing - himself said, "Perhaps, their most profound effect may prove to be theoretical".
- 14. BIBLIOGRAPHY QUBIT.ORG WIKIPEDIA.ORG QUANTUM COMPUTING(STANFORD ENCYCLOPEDIA) Bennett, C. et al. (1997), ‘Strengths and weaknesses of quantum computing’, SIAM Journal on Computing, 26(5): 1510–1523. SCIENCEDAILY.COM

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