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Entanglement The phenomenon by which two or more qubits share the same quantum states and are correlated regardless of distance from each other is called entanglement . A change to one of the entangled qubits directly impacts the other ’ s behavior .
Superposition and entanglement enable quantum computers to perform computations simultaneously rather than sequentially or in parallel . This ability is a key difference between classical and quantum machines .
The engineering challenge
Quantum computers are susceptible to noise and this causes them to decohere . Decoherence is the collapse of the quantum state . It is a loss of information and a corruption of the calculations being performed .
Since quantum computers work at the atomic or subatomic level , the control and measurement signals within them are tiny . Because of this , minimizing environmental noise becomes critical .
Qubits in a superconducting quantum computer
Superconducting quantum computers , one type of quantum computer , use the properties of superconducting materials to create a circuit that acts like an artificial atom . These circuits are built using a process similar to that used for manufacturing semiconductors .
The state of these qubits is controlled with microwave radiation and entangled using electronic coupling . As you might imagine , the energy levels in these circuits are very small and require isolation from the external environment . For this type of quantum computer , special cooling technology is used to maintain coherence .
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