Experimental Demonstration of a Quantum Circuit using Linear Optics   Gates
  One of the main advantages of an optical approach to quantum computing is the fact that optical fibers can be used to connect the logic and memory devices to form useful circuits, in analogy with the wires of a conventional computer. Here we describe an experimental demonstration of a simple quantum circuit of that kind in which two probabilistic exclusive-OR (XOR) logic gates were combined to calculate the parity of three input qubits. 
T.B. Pittman, B.C Jacobs, and J.D. Franson