What is quantum entanglement?
A link between qubits in which their measurement results are correlated in a way no prearranged plan could produce.
Two entangled qubits can share one state, such as “both 0 or both 1, equally likely”. Measure either and you get a random result, and the other one, measured later, matches it, even if they are far apart.
Matching results alone would be easy to fake: put one red and one blue card in two envelopes, and opening one tells you the other. Entangled qubits go further. When each is measured in different ways, the results agree more often than any envelope-style plan can manage. Experiments testing this won the 2022 Nobel Prize in Physics.
Entanglement can’t send a message. Each side’s results look random on their own, and the correlation only shows up when the two lists are compared, which takes an ordinary signal.
Related
- QubitThe basic unit of a quantum computer: it can be 0, 1, or a blend of both until it is measured.
- MeasurementReading a qubit. It returns 0 or 1 at random, with chances set by the squared amplitudes, and ends the blend.
- Quantum gateAn operation that changes the amplitudes of one or more qubits, the quantum version of a logic gate.
- No-cloning theoremThe rule that an unknown quantum state can't be copied.