Research On Laser Pulse Generation For Quantum Teleportation

As a key technology in photonic quantum information technology,independent photon source interference plays a substantial role in quantum teleportation and entanglement swapping,and also has a high requirement on the pulsed light sources used in it,i.e.,faster modulation rate,smaller time jitter,and narrower pulse width are required.This thesis proposes and demonstrates a narrow pulse generation scheme for quantum teleportation,based on combing semiconductor lasers,gain-switching,and injectionlocking technologies.Such a scheme could effectively suppress the inherent high time jitter of the gain-switched semiconductor laser,narrower its spectral width during dynamic modulation,and improve the visibility of interference between independent photon sources,finally improving the system performance of quantum teleportation.This thesis introduces the application of pulsed laser generation technology in quantum key distribution,quantum random number generations,and quantum teleportation systems,with the basic principle of quantum teleportation system described detailly.The mechanisms of gain-switching and injection-locking technologies are analyzed based on the rate equations of semiconductor laser,with numerical simulations.In experiment,hundred-picosecond laser pulses are generated by gain-switching technology,and their output power,time jitter,and spectral width are further optimized by the injection-locking technology.The main contents of this thesis are as follows:（1）Firstly,based on the rate equations of the semiconductor laser,the theoretical analysis of the gain-switching process in semiconductor laser is carried out.Numerical simulations are performed to reveal the time-evolution of injection current,carrier density,and photon number density during a single gain switch process.（2）Secondly,a semiconductor laser is made based on a homemade driving circuit and commercial laser diode,and its I-V characteristic curve,as well as the working wavelength versus injection current intensity have been measured.A digital driving circuit is designed and developed,and a wavelength-tunable narrow-pulse gain-switched laser is further realized.The pulse width,time-domain waveform,spectral characteristics,and time jitter of the output pulses from this laser have been measured.The results show that the pulse can be as narrow as 120 ps.（3）Thirdly,the working characteristics of injection-locked laser are analyzed by numerical methods,such as the bathochromic shift of the resonator cavity and the frequency-locking range of the injection-locked laser.An injection-locking system is established by injecting direct current（DC）laser into a gain-switched semiconductor laser,and the variations of the spectrum,power,and frequency detuning before and after injection have been measured.Based on the experimental results with DC laser injectionlocked laser,the experimental study of pulse injection-locking is carried out.The measured results show that the spectral width can be narrowed by 0.02 nm,while the time jitter of pulse period can be reduced by 60 ps.