Nanosecond Pulse Laser System For A Triggered Single-photon Source Based On A Trapped Single Atom

With the rapid development of quantum information,as the representative of the quantum systems,photons almost are involved in any quantum information processing.The quantum information can be encoded in the photons state,such as frequency,polarization,wave profile and orbital angular momentum.The photon can also be used for quantum compute,flying qubit in remote quantum network,media in hybrid quantum systems.In recent years,non-cloning single-photon source is considered as a key part of quantum information and widely used in quantum communication.Currently the single photon source generated from a variety of physical systems has been extensively studied,including single atom,single ion,single molecule,single NV color centers in diamond,quantum dots,spontaneous parametric down conversion,and atomic ensemble based on four-wave mixing processes.In addition,the coupling between radiation field and optical cavity has been investigated,which could increase the output efficiency of single photon.Single photon source based on neutral atoms has a narrow radiation spectrum width,which is easy to directly couple to cold atom for the memory,which has potential value for constructing quantum network.After cooling and trapping a few of cesium atom in magnetic-optical trap(MOT),we load a single atoms to a conservative potential micro optical dipole trap and then prepare the trapped atom with a specific hyperfine state or Zeeman state by optical pumping.The approximate two level system is periodically excited into the excited state by a homemade nanosecond pulse laser system.An ensemble lens with numerical aperture of 0.29 collect the spontaneous emission photons from the trapped atom.The spontaneous photons are then coupled to the optical fiber by a compound lens,which are detected by single photon detectors or subsequent application.This paper includes the following chapters:1.Recent developments and significant achievements in achieving the single-photon source are introduced.Efficient coupling light pulse to atoms requires the resonance pulse with a suitable peak intensity and the pulse duration which should be short compared to the excited state lifetime.2.For solving the problem of the unstable output power of z-cut waveguide electro-optic intensity modulator(EOIM),the precision temperature control technology is adopted to suppress laser power drift.At the OFF state,the power drift of MZ-EOIM with temperature stabilized and without temperature stabilized are 0.42?W/h and 6.35?W/h,respectively.Choosing a proper matching temperature,the symmetry of MZ-EOIM can be optimized near perfect state,and the static ON/OFF ratio can be increased from a typical default value of 20 dB to 41dB.3.The output light pulses from EOIM is injected to a DFB diode laser to achieve synchronous pulses with a high peak intensity of 50mW.Based on the dynamic procession and experimental parameters of the injection locking range,it can be inferred that the minimum injection locked time of a stable locked state is about 19ps.The threshold of injection power is about one hundred microwatt,which depends on the frequency detuning of the master laser to slave laser.For the OFF state,injection the slave is not locked and free runs with blue detuning of 32.6GHz to the atomic transition line.4.The pulse light with high ON/OFF ratio is used to excite a single neutral atom to achieve a triggered single photon source.Subtracting the background count,the two-photon probability is less than 4.2%.Actually count rate of measured single-photon on average is 636 per second.The triggered single photon source has be widely used with the applications including verification of undistinguished photons,generation of true random number,deterministic single encoded photon stored in the cold atomic ensemble for generating quantum repeater.