Friday, October 9, 2009

Quantum Foundation Lecture part 2

Today's lecture was more like a question answer session. It was natural that students will come up with many doubts after yesterday's overdose..:P. Most of the time Prof Roy had to answer very basic doubts raised by the students. He started with two comments regarding yesterday's class: Bell's inequality is fully relativistic and violation of local reality by Quantum Mechanics does not mean that information can carried from one place to another with speed more than the speed of light in vacuum. Then he gave an introduction to density matrix for pure and mixed states. Then he talked about separable pure states. These states are basically non-entangled and obeys local reality, Bell's inequality. He then talked about N-particle correlation function and how difficult it is to find out whether the N particle states are entangled or not. Since violation of local reality grows exponentially with number of particles and so does entanglement, hence it can speed-up quantum computation very efficiently. He skipped the latter half of the lecture since he ran out of time answering the doubts of the students and will probably talk about that in the next lecture which is on 12th October.

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