Bell state

Meaning

Noun

• One of a set of four entangled states, namely $|\backslash Phi^+\backslash rangle\; =\; \{1\backslash over\; \backslash sqrt\{2\}\}\; (\; |00\backslash rangle\; +\; |11\backslash rangle\; )$, $|\backslash Phi^-\backslash rangle\; =\; \{1\backslash over\; \backslash sqrt\{2\}\}\; (|00\backslash rangle\; -\; |11\backslash rangle\; )$,    $|\backslash Psi^+\backslash rangle\; =\; \{1\backslash over\; \backslash sqrt\{2\}\}\; (|01\backslash rangle\; +\; |10\backslash rangle\; )$, and $|\backslash Psi^-\backslash rangle\; =\; \{1\; \backslash over\; \backslash sqrt\{2\}\}\; (|01\backslash rangle\; -\; |10\backslash rangle\; )$, where $|xy\backslash rangle\; :=\; |x\backslash rangle\; \backslash otimes\; |y\backslash rangle$; these are the simplest examples of entangled states.

Origin

• Named after John Stewart Bell (1928–1990), Irish physicist.