All quantum states of light exhibit field fluctuation even in the vacuum state. There are many physical phenomena which result from vacuum fluctuation. The most prominent example is the spontaneous radiation. In quantum optics and laser physics people have succeeded in producing theoretically even a squeezed state of light that fluctuates at a lower noise level than the vacuum fluctuation. The application of squeezed light will provide new opportunities for high precision measurements. In the present work we consider the quantum superposition of state 0 1 01 y =a + b and work out the variances of the quadrature operators 1 ˆX and 2 ˆX . We have shown that for some values of parameters α and β, the quadrature variances become less than the vacuum fluctuation. This indicates the principle of manipulating vacuum.
