Quantum computersQuantum computers work with quantum entanglement to solve problems exponentially faster than any other kind of computer.
Recent experiments have shown how to entangle several bits together.
Specific problems to be solved are factoring of large numbers, which is very important to cryptography, and optimization and solution of NP-Complete problems.
Quantum computers may not be practical, because of the energy needed to keep it together. Some critics have suggested that they cannot scale to useful sizes.