“…Notice that |n 1 , n 2 , n 3 is eigenstate of the Penning trap Hamiltonian with eigenvalue E n 1 ,n 2 ,n 3 = ω 1 (n 1 + 1/2) − ω 2 (n 2 + 1/2) + ω 3 (n 3 + 1/2) ≡ E(n 1 , n 2 , n 3 ). In particular, the extremal state |0, 0, 0 has eigenvalue E 0,0,0 = (ω 1 − ω 2 + ω 3 )/2, i.e., it is neither a ground nor a top state since its energy is "in the middle" of the spectrum of H. Following [15], it is seen that there is an intrinsic algebraic structure for our system, which is characterized by a linear relationship between the Penning trap Hamiltonian H and the three number operators N k :…”