In principle, acoustic waves can be used for computing. However, as they are difficult to manipulate when propagating through air, one usually uses phonons, which are their counterpart in solids. In detail, a phonon is a wave which results from the movement of atoms in a solid. In more detail, in a solid the atoms are located on fixed positions forming a regular lattice. When one of them is moved out of its equilibrium position, it affects the position of the neighbouring atoms due to their interaction. Thus, the distortion can propagate through the solid in form of a wave, which can be longitudinal or transversal. The physical assumption of periodicity for the lattice then leads to a quantization condition for the possible energy levels.
For computing purposes devices based on phononic metameterials were supposed. Based on them, simple logic gates were constructed like AND, OR, XOR and NOT were constructed. To realize them, two signals were combined such that they interfer in a constructive and destructive way due to their phase difference. By defining threshold values for the amplitude, one can define waves as coputational binary states 0 and 1.
Variables of Phonons
- amplitude
- phase
- wavelength / frequency