| Summary: | 碩士 === 國立清華大學 === 物理系 === 104 === Generating and detecting single photons are important research topics in the field of quantum information. We carry out the experiment in an atomic vapor cell at the room temperature, filled with rubidium atoms consisting of only one stable isotope Rb-87. Our goal is to produce a pair of time-correlated single photons, called biphotons, for the experiments of quantum information manipulation in our lab. Atomic systems at room temperature are much simpler than those at low temperature. In practical applications, these systems have relatively high feasibility. Furthermore, our system adopts a continuous wave (continuous-wave) laser, which can produce single photons continuously. These single photons can carry quantum information. And this technique is widely used in quantum communication and quantum computation.
We use four-wave mixing, a nonlinear optical mechanism, to generate a single photon. Experimentally, two strong lights are shined into the rubidium vapor chamber, which are called pump field and coupling field. At the same time, the system spontaneously radiates two single photons, which are called signal and probe fields. The four lights mentioned above are overlapped in space and travel in the same direction. Due to the high powers of the pump field and the coupling field (both are about 2×〖10〗^16count/s), extracting the signal of single photons is extremely difficult. Therefore, reducing the background (pump and coupling) noises is a very important work. If signal and probe photons loss that is eliminated, reducing the production rate. This thesis aims to discuss how to get rid of the large noises of the strong lights without eliminating the single photons. We use birefringent crystal polarizers and etalon filters to achieve the best signal-noise ratio. Currently, we can reduce the background noise to about ten thousand photons per second. Our goal is to lower this value to around one thousand photons per second.
|
|---|
