NONLOCALITY IN QUANTUM COMPUTING

The operation of a quantum computer is inherently nonlocal due to the entanglement of separated quantum gates. This paper is concerned inste ad with the use of nonlocal effects to construct the quantum gates the mselves. A nonlocal interaction in which pairs of atoms exchange two p hotons is expected to produce a large nonlinear phase shift. An intere sting feature of this effect is that energy is not conserved at the lo cation of an individual atom but it is conserved overall. The prelimin ary results from a series of experiments in a sodium vapor cell are in apparent agreement with the predictions of the theory. These nonlinea r phase shifts can be used to construct quantum logic gates, such as a Controlled-NOT.