In classical mechanics, Bertrand's theorem states that among central force potentials with bound orbits, there are only two types of central force potentials with the property that all bound orbits are also closed orbits: (1) an inverse-square central force such as the gravitational or electrostatic potential V ( r ) = − k r , {\displaystyle V(\mathbf {r} )={\frac {-k}{r}},} and (2) the radial...

In computational complexity theory and quantum computing, Simon's problem is a computational problem conceived to showcase the efficiency increase a quantum algorithm could have over a classic one. Although the problem itself is of little practical value, it is interesting because it provides an exponential speedup over any classical algorithm (in a black box model). The problem deals with the model of decision tree complexity or query complexity and was conceived by Daniel Simon in 1994. Simon exhibited a quantum algorithm, usually called Simon's algorithm, that solves the problem exponentially...