Macroscopic Quantum Jumps from a Two-Atom System
We present an analysis of the macroscopic quantum jumps (MQJ) [1,2,4] that can be produced when two identical two-level atoms separated by a distance d are irradiated by a laser having wavelength λ0, with λ0 » d. The laser is resonant with the same ground to excited-state transition in each atom. The problem is conveniently described in terms of the eigenstates  of the two-atom system in the absence of any applied field (Fig.1). Denoting the ground and excited states of atom i(i = 1,2) by | gi > and | e i >, respectively, the appropriate eigenstates are given by | E >=| e 1 e 2 >, | S >= 1/\(\sqrt 2 \) (|e 1 g 2 > + | g 1 e 2 >), | G >=| g 1 g 2 > and | A> = 1\(\sqrt 2 \) (| e 1 g 2 > − | g 1 e 2 >); states | E >, | S > and | G > are symmetric and state | A > is antisymmetric on interchange of the atoms. Energy levels of states | S > and | A > are shifted from those of the non-interacting two-atom system by an amount V. For λ0 » d, the antisymmetric state has a small, but nonvanishing decay rate, Γ A ≅ (2πd/ λ0)2 Γ/5 while the symmetric state decays with a rate Γ S ≅ 2Γ (Γ = decay rate of a single atom). For the level scheme of Fig. 1, such decay rates lend themselves to the possibility of observing MQJ when the system is pumped by an external field.
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