Study In The Quantum Measurement Of Frequency Entangled Photon Source

Time and frequency is strategically important national resources, one of itsessential part is the clock synchronization system. Modern clocks have been improvedto such a level, that the resolution and accuracy of the comparison techniques havebecome the limiting factors to determine the accuracy of positioning and timing. Forclassical clock synchronization methods, their accuracy is limited by the shot noiselimit. However, in recent years, quantum clock synchronization technique based onthe nonlocal correlations of quantum entanglement state can potentially break throughthis limit and achieve the Heisenberg limit, reaching the timing accuracy belowsub-picosecond.High quality frequency-entangled resources play a key role in the quantum clocksynchronization systems, its characterization and measurement method has a directeffect on the final synchronization accuracy. In this thesis, we demonstrated thegeneration and characterization of a coincident-frequency-entangled photon source.Experimental setup and automation measurement system are described firstly. Thenthe generation and quantum coincidence measurement of the frequency entangledphotons are addressed, where both the direct time coincidence measurement and theseconder-order quantum interference measurement results are shown. The theoreticalstudy on the visibility of HOM dip and the best working temperature of thedown-convert crystal are further performed and compared with the experimentalresults. The agreement implied the effect of the spectral bandwidth of the pump on theinseparability of the generated coincident-frequency entanglement. In summary, astudy in the generation and measurements of entangled photons was present in thisthesis, the results constitutes a solid basis for the demonstration and apply of thequantum clock synchronization algorithm.