Quantum communication involves communication via individual quantum states, most often photon states. Quantum communication methods allow opportunities to compress large amounts of data into a small number of photons, as well as to evade disruption by disruptive effects such as turbulence. In addition, quantum cryptography (or more precisely quantum key distribution (QKD)) allows greatly enhanced communication security. Although there are a number of practical problems in the way before quantum communication becomes an everyday process, advantages have spurred a large influx of funding into the field from both government and industry. At least one commercially available smartphone already uses weak Poisson pulses to generate single-photon random number generation for QKD, in order to improve data security. This chapter gives an introduction to quantum cryptographic protocols.