Alan Turing introduced the Turing machine in 1936. All classical computers are Turing machines, and are thus limited to problems that Turing machines can solve. No matter how fast they become, there will be certain problems that will remain unsolvable for these machines. Therefore, if we wish to solve these problems we must create a new paradigm for future machines to operate on.

Quantum computing is such a paradigm. The premise is that by exploiting the rules of quantum mechanics we can create computers that can both solve certain problems faster than classical computers, and solve previously unsolvable problems. While there has been much advancement made by physicists and computer scientists in the theoretical realm of quantum computing, including the creation of quantum Turing machines and an algorithm for factoring large numbers, actually building quantum computers to test theory and run algorithms has proven quite difficult.

My project consisted of building the most basic part of a quantum computer, a quantum logic gate. For this purpose I chose to use a laser based system. Lasers meet the necessary criteria for quantum computation (interference, entanglement, and superposition). They also proved to be relatively cheap and easy to work with. The result was a working XOR (exclusive or) gate, constructed of commonplace optical elements, which met all criteria except entanglement (accomplishing this would be possible, but more costly and time consuming). Theoretically, using large numbers of similar gates in conjunction would allow the construction of a working quantum computer.

**Scott Tolliver, ’02** Ashland, WI

Majors: Physics and Computer Science

Sponsor: Derin Sherman