The '''Bell measurement''' is an important concept in [[quantum information science]]: It is a joint quantum-mechanical measurement of two [[qubit]]s that determines in which of the four [[Bell state]]s the two qubits are in.
If the qubits were not in a Bell state before, they get projected into a Bell state (according to the projection rule of [[quantum measurement]]s), and as Bell states are [[entanglement|entangled]], a Bell measurement is an entangling operation.
It is the crucial part of [[quantum teleportation]] (see there).
In current experiments which use [[photon]]s as qubits, Bell measurements can only be partly realized as two of the Bell states cannot be distinguished with optical techniques. In Bell measurements of [[ion]] qubits in [[ion trap]] experiments, the distinction of all four states is possible.
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[[Category:Evolutions and Operations]]
