TY  - JOUR
PB  - American Physical Society
ID  - 10.1103/PhysRevFocus.19.12
TI  - Four States are Better than Two
JF  - Physical Review Focus
JA  - Phys. Rev. Focus
J1  - FOCUS
VL  - 19
IS  - 
SP  - 12
EP  - 
PY  - 2007/04/20/
UR  - http://link.aps.org/doi/10.1103/PhysRevFocus.19.12
A1  - Sherwood, Jonathan
ER  -