Page "Superluminal communication" Paragraph 6

According to the currently accepted theory, three of those four phenomena do not produce superluminal communication, even though they may give that appearance under some conditions.

The third, tachyons, arguably do not exist as their existence is hypothetical ; even if their existence were to be proven, attempts to quantize them appear to indicate that they may not be used for superluminal communication, because experiments to produce or absorb tachyons cannot be fully controlled.