# Week 4 Day 2

Published on: Tue Jun 28 2011

The morning started off with working on Shor’s Algorithm, as usual. I was writing a new section on the Controlled-U gate. There was an excellent question, “What is a logic gate?”  I took off explaining how binary works, which lead to how binary addition works. At which point another student wandered over and asked, “Have you ever build an adder circuit?” Which lead to quite an excited discussion about the plan to build an optical Turing machine that became a project to build an optical AND gate and reprised the difficulty of actually creating one. Then it was time for the lunch meeting.

The lunch meeting was on heat conductivity, and I had the chance to hold a diamond chip and ‘cut’ ice. It went right through the chuck of ice, but it quickly cooled down to. One thing that stuck with me is that solids are really gases, except they are composed of two different gases. Phonons and Electrons. Fascinating point of view.

When we came back from lunch I was talking with another student about circular polarization of light. We did a miniature experiment, where we verticality polarized light, and then measured the intensity. Next we added a quarter-wave plate and measured the intensity. It remained the same, except for a small drop due to reflection off the wave-plate. Next we inserted a horizontal polarizer, and the intensity continued to remain the same. As we rotated the polarized it continued to remain nearly the same, except for some minor oscillations, which we attributed to reflections from the polarizer.