a trapped-atom quantum memory (PDF) - MIT

ROTATE SUPERPOSITION-BASIS BELL STATES INTO PURE-BASIS BELL STATES
π/2 pulses
a
b
a
b
c
d
c
d
2
2
OLD BELL STATES
|A + >=|c 2 >+|b 2 >
|A - >=|c 2 >-|b 2 >
|B + >=|d 2 >+|a 2 >
|B - >=|d 2 >-|a 2 >.
NEW BELL STATES
|a + >=|c 2 >
|a - >=|b 2 >
|b + >=|d 2 >
|b - >=|a 2 >.