*Quantum computing* is one of the holy-grails and the most-spoken about application of modern [[Quantum Technologies|quantum technology]]. The idea is to build a universal quantum processing device that can solve practically relevant problems faster than any classical computing device.  Building a quantum computer is a balancing act between isolation and control. ![[isolation_vs_control.excalidraw.light.svg]] On the one hand, [[Qubit|qubits]] should be well isolated from their surroundings to avoid [[decoherence]]. [[Quantum Information|Quantum information]] is difficult to store and it gets lost over time, even on the best quantum devices. Thus, the information must be periodically corrected. This is the role of [[Quantum Error Correction|quantum error correction]]. The basic idea is to combine many noisy (bad) qubits into one [[ Logical Qubit|logical (good) qubit]]. On the other hand, we cannot fully isolate the *quantum computer*, since we would like to apply [[Quantum Gates|quantum gates]] on the [[Qubit|qubits]] to manipulate the stored [[Quantum Information|quantum information]]. Most modern quantum devices are running without error correction, they are so called [[Near-Term Quantum Device| near-term devices]]. Most quantum algorithms with a provable advantage, however, need [[Fault-Tolerant Quantum Computer| fully error-corrected quantum computers]]. Thus, there is still some way to go until we see a practical advantage of quantum computers. >[!read]- Further Reading >- [[Quantum Technologies]] >[!ref]- References