Attempts have been made to assess the physical mass of information by estimating the mass of electrons feeding the power-guzzling computers and devices making up the Internet, the result being around 50 g. One cannot store information with photons, but it is possible to communicate information with them, either through an optical fiber or via free space. In an exploration of the fundamental lower limits of the transferred mass related to information, it is, therefore, more proper to use photons than electrons. In an ideal case, a single photon can carry one bit of information, for example, by using the two orthogonal polarization modes to represent the two bit values. Finally, one should note that it is possible to communicate without emitting any signal energy into the communication channel, namely, by modulating the statistical properties of its thermal noise or quantum noise.
