Dear fellows, please help me to imagine the physical working of a quantum computer (QC). I have read here ( http://www.cs.rice.edu/~taha/teaching/05F/210/news/2005_09_16.htm ) that the basic idea behind it is the phenomenon that you can find in the Mach–Zehnder interferometer But how come this two together exactly? A computer have (say) 3 parts: input, a processing apparatus, and output. Consider the following schema of a 1 qbit QC (on the picture: two inputs, one output and a black box in the middle) I'd like to outline the simplest task possible. Let's say that the I1 and I2 are 1 bit "numeric" inputs ( 0 or 1 ) and the task of the QC is to tell which number is bigger, and tell "1" as answer on the "A1" if the I1 is the greater. Since it is a QC, the inner state of the 1 qbit will represent all of the possible answers at once. The task of the black box is to make the inputs on the left to fit to the system, allow the quantum states to process and read out somehow the correct answer and put it on the output line. I think that this task should be easy to implement. (If I'm wrong, I accept any other tasks as example) Would someone be so kind and draw a simple schema, with beamsplitters (or any kind of apparatus that is use to be set up in a system like this -- for example bbo-s, mirrors, etc) that implements the task of the black box described above? It would be very effective and enjoyable to see a complete schema that represents a QC for a specific simple task, from the input to the output. I'd love it. Thank you very much!