Idea Ripper // ArchiveCards: 1555 [Live] | Updated: 2026-10-14
Card #c102IR // #c102Synthesis

Whereas if Alice has measured her qubit, then Bob's qubit has collapsed – it is either in state 0, or state 1 (each with probability 1/2).

— In our words · Source: Quantum Computing (S. Herbert)

[Use when]

When someone claims spooky action equals a phone.

[Why it matters]

Entanglement plus local measurement does not give Bob Alice's message — only shared randomness after collapse.

More from Quantum Computing

#c98The qubit can then optionally be measured, in which case either of the states |0⟩ and |1⟩ is observed, as the measurement apparatus detects…When "observe" is used as if it were free. #c99If a measurement is not taken, the qubit will be in a superposition of |0⟩ and |1⟩, and its onward evolution can involve the interference…When explaining why you cannot peek mid-algorithm without killing the advantage. #c100Together, postulates 1 and 4 state that an n-qubit quantum state is represented by a 2^n-element complex unit vector.When classical intuition expects linear growth in bits.