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Quantum Computers

Fact -or- Fantasy?

CS Senior Seminar

Imagine a computer whose memory is exponentially larger than its apparent physical size; a computer that can manipulate an exponential set of inputs simultaneously; a computer that computes in the twilight zone of space. You would be thinking of a quantum computer. Relatively few and simple concepts from quantum mechanics are needed to make quantum computers a possibility. The subtlety has been in learning to manipulate these concepts. Is such a computer an inevitability or will it be too difficult to build?

By the strange laws of quantum mechanics, Folger, a senior editor at Discover, notes that; an electron, proton, or other subatomic particle is "in more than one place at a time," because individual particles behave like waves, these different places are different states that an atom can exist in simultaneously.

What’s the big deal about quantum computing? Imagine you were in a large office building and you had to retrieve a briefcase left on a desk picked at random in one of hundreds of offices. In the same way that you would have to walk through the building, opening doors one at a time to find the briefcase, an ordinary computer has to make it way through long strings of 1’s and 0’s until it arrives at the answer. But what if instead of having to search by yourself, you could instantly create as many copies of yourself as there were rooms in the building all the copies could simultaneously peek in all the offices, and the one that finds the briefcase becomes the real you, the rest just disappear. – (David Freeman, discover )

David Deutsch, a physicist at Oxford University, argued that it may be possible to build an extremely powerful computer based on this peculiar reality. In 1994, Peter Shor, a mathematician at AT&T Bell Laboratories in New Jersey, proved that, in theory at least, a full-blown quantum computer could factor even the largest numbers in seconds; an accomplishment impossible for even the fastest conventional computer. An outbreak of theories and discussions of the possibility of building a quantum computer now permeates itself though out the quantum fields of technology and research.

It\'s roots can be traced back to 1981, when Richard Feynman noted that physicists always seem to run into computational problems when they try to simulate a system in which quantum mechanics would take place. The calculations involving the behavior of atoms, electrons, or photons, require an immense amount of time on today\'s computers. In 1985 in Oxford England the first description of how a quantum computer might work surfaced with David Deutsch\'s theories. The new device would not only be able to surpass today\'s computers in speed, but also could perform some logical operations that conventional ones couldn\'t.

This research began looking into actually constructing a device and with the go ahead and additional funding of AT&T Bell Laboratories in Murray Hill, New Jersey a new member of the team was added. Peter Shor made the discovery that quantum computation can greatly speed factoring of whole numbers. It\'s more than just a step in micro-computing technology, it could offer insights into real world applications such as cryptography.

"There is a hope at the end of the tunnel that quantum computers may one day become a reality," says Gilles Brassard of University of Montreal. Quantum Mechanics give an unexpected clarity in the description of the behavior of atoms, electrons, and photons on the microscopic levels. Although this information isn\'t applicable in everyday household uses it does certainly apply to every interaction of matter that we can see, the real benefits of this knowledge are just beginning to show themselves.

In our computers, circuit boards are designed so that a 1 or a 0 is represented by differing amounts of electricity, the outcome of one possibility has no effect on the other. However, a problem arises when quantum theories are introduced, the outcomes come from a single piece of hardware existing in two separate realities and these realties overlap one another affecting both outcomes at once. These problems can become one of the greatest strengths of the new computer however, if it is possible to program the outcomes in such a way so that undesirable effects cancel themselves out while the positive