Hilbert space quantum mechanics is noncontextual

It is shown that quantum mechanics is noncontextual if quantum properties are represented by subspaces of the quantum Hilbert space (as proposed by von Neumann) rather than by hidden variables. In particular, a measurement using an appropriately constructed apparatus can be shown to reveal the value of an observable A   possessed by the measured system before the measurement took place, whatever other compatible ([B,A]=0[B,A]=0) observable B may be measured at the same time.

► Idea that quantum mechanics is contextual comes from using hidden variables. ► Hilbert subspaces are the proper way to represent quantum properties. ► Using subspaces one can demonstrate that quantum mechanics is noncontextual.