Qubit, a quantum bit, or qubit (sometimes qbit) is a unit of quantum information
The concept of the qubit was unknowingly introduced by Stephen Wiesner in 1983, in his proposal for unforgeable quantum money, which he had tried to publish for over a decade.
Hence, followed Einstein, Podolsky, and Rosen in 1935 in their famous "EPR paper", there is something missing in the description of the qubit pair given above—namely this "agreement", called more formally a hidden variable.
Research to improve these technologies ultimately led to our understanding the essentially digital nature of information, quantized down to the unit of the bit (or qubit).
In 2005, Sankar Das Sarma, Michael Freedman, and Chetan Nayak proposed a quantum Hall device which would realize a topological qubit.