Accurate measurement method for refractive index in a high efficiency interaction-free measurement system

The state of the quantum system will inevitably be disturbed and changed in the testing process. Using interaction-free measurement (IFM), the information can be extracted without any interaction between objects and photons or particles. Here we present a novel approach that the refractive index can be measured accurately with "no-touch" measurement between testing materials and light beam. The design system is a non-traditional model of interaction-free measurement with an unbalanced Mach-Zehnder interferometer (UMZI), which is combined with the chain quantum Zeno effect and the technique for spatial separation of light field. We select two beams with different intensity distribution in cross-section and different frequency as the transmission source, and the refractive index of samples can be obtained from the contrast degree of two beams under the condition of a few beam splitters existing. The scheme could prevent the damage to the radiation-sensitive optical materials, and provide a new idea for the research and application of precision measurement.