Using the technique of integration within an ordered product of operators we present a convenient approach for introducing the squeezing operator for the entangled states of two entangled particles with different masses. We also introduce one-sided squeezing operators.
For two unequal-mass particles, we construct the entangled state representation and then derive the corresponding squeezing operator. This squeezing operator has a natural realization in the entangled state representation, which exhibits the intrinsic relation between squeezing and quantum entanglement. This squeezing operator involves both two-mode squeezing and the direct product of two single-mode squeezings. The maximum squeezing occurs when the two particles possess equal mass. When the two particles' mass difference becomes large, the component of the two single-mode squeezings becomes dominant.
We introduce the three-mode entangled state and set up an experiment to generate it. Then we discuss the three-mode squeezing operator squeezed | p , χ 2 , χ 3 ⟩ → μ -3/2 | p /μ, χ 2 /μ, χ 3 /μ ⟩ and the optical implement to realize such a squeezed state. We also reveal that c -number asymmetric shrink transform in the three-mode entangled state, i.e. | p , χ 2 , χ 3 ⟩ → μ -1/2 | p /μ, χ 2 , χ 3 ⟩, maps onto a kind of one-sided three-mode squeezing operator exp {iλ/3 (∑ i =1 3 P i ) (∑ i =1 3 Q i ) − λ/2}. Using the technique of integration within an ordered product (IWOP) of operators, we derive their normally ordered forms and construct the corresponding squeezed states.