valid bit
1.In the Information theory investigation for the quantum cryptography, how we compute the quantity of information that the eavesdropper Eve and legal receiver Bob acquire, and the characteristic of the quantity of information, the boundary of quantity of information, the containing quantity of information in a parity bit etc, are the key problems to quantum cryptography. Only the one know the quantity of information Eve acquiring, then legal correspondent can adopt the valid measurement and guarantee the correspondence safety.
