# Bit corresponds to postion? Sign corresponds to mometum?

Hi! I was going through the lectures on Quantum Mechanics and Quantum Computation by Umesh Vazirani. In one of his lectures he defines the quantum state of a two energy level system in |0> , |1> basis where |0> corresponds to ground state and |1> corresponds to excited state. Then he defines another orthonormal basis |+> | – > where |+> equals (1/sqrt2) |0 > + (1/sqrt2) |1> and | – > equals (1/sqrt2) |0 > – (1/sqrt2) |1>. He goes on saying that when measurement is made **in |0> |1> basis we are** **measuring the BIT** and when measurement in done** in |+> | – > basis we are measuring** **SIGN**. Then he adds that ” **in a sense BIT corresponds to position and SIGN corresponds** **to momentum**“, which left me confused. What does he mean by that? Was it just meant as an analogy to Heisenberg’s Uncertainty principle?

When I looked up these lectures, I found this link https://www.classcentral.com/course/edx-quantum-mechanics-and-quantum-computation-613.

To help us out, **can you tell us where in the lectures he makes this specific statement? ** The Heisenberg Uncertainty Principle is usually introduced in the form of it being “impossible to know both the position and the momentum of a particle with absolute accuracy”. However, many systems of interest for quantum computing are not based on moving particles, but on the spin of particles, where the uncertainty principle manifests itself a different way.

This article in Scientific American may interest you: https://www.scientificamerican.com/article/atomic-spins-evade-heisenberg-uncertainty-principle/