Quantum computing has been slowly progressing both as a technology and potential new platform business (see my previous column, "The Business of Quantum Computing," Communications, Oct. 2018). But another application of quantum mechanics that has attracted increasing attention is quantum communications.12 In fact, the 2022 Nobel Prize in Physics was awarded last October to three scientists for their experiments proving the reality of quantum entanglement, which is fundamental to quantum cryptography and secure communications.11 How did we get from quantum computing to quantum communications, and what is the business potential?
The same two physical phenomena that inspired quantum computing motivate quantum communications. The first is superposition. A quantum bit or "qubit" can behave as a wave as well as a discrete particle and exist in "super-positions" of states. That turns out to be the equivalent of 0, 1, or both simultaneously, rather than just 0 or 1, as in a digital computer. This characteristic as well as quantum interference (similar to how waves can amplify or "interfere" with each other) are fundamental to how quantum computers can potentially achieve exponential increases in computing power. The second is entanglement. This is the ability of two quantum particles (such as one photon split into two) to become connected and form a "system." The system pair can retain the specific correlations of the individual particles (such as a positive or negative spin in their energy states, which can translate into 0 or 1), even when physically separated.