A computer that harnesses phenomena from quantum mechanics in order to perform much more efficient computations than older, classical computer technologies are capable of.
Quantum computing is the study of how to use phenomena in quantum physics to create new ways of computing. The basic unit of information in quantum computing is a qubit. Unlike a traditional computer bit, which is a binary digit characterized as either 0 or 1, a qubit can be a coherent superposition of both 0 and 1. The power of a quantum computer increases with each qubit that is added. However, adding more transistors will not add power linearity, as it would with traditional computers.
Superposition and entanglement are the two features of quantum mechanics used for quantum computations. These features empower quantum computers to handle operations at speeds that are exponentially higher as compared to traditional computers, while also consuming a lot less energy in the process.
A very simple definition of a quantum computer is a computer that harnesses phenomena from quantum mechanics in order to perform much more efficient computations than older, classical computer technologies are capable of.
The field of quantum computing originates in the 1980s, when it was discovered that certain computational problems can better be tackled using quantum algorithms than with the classical counterparts in use at the time.
Quantum computing could significantly contribute to the fields of finance, military affairs, artificial intelligence, big data, etc.
In the cryptocurrency sector, there has been some debate about how the advent of quantum computing will affect the security of networks such as Bitcoin (BTC) by posing a threat to the resilience of their cryptography. Developers and mathematicians are therefore working to investigate how it might be possible to create quantum-resistant cryptography that could future-proof these networks.