【作者】 王晓波；

【导师】 贾锁堂； 肖连团；

【作者基本信息】 山西大学 ， 光学， 2012， 博士

【摘要】 量子信息技术是量子物理与信息技术相结合发展起来的新学科,已成为目前最具吸引力的前沿领域之一,涉及众多学科领域,在量子信息领域开展的工作主要有量子通信、量子计算、量子成像等方面,具有经典信息技术无法比拟的优势和前景。单光子的产生、检测和操纵不断开拓光物理应用的新领域。由于在量子信息领域的广泛应用,单光子源的研究引起了人们的极大兴趣。一方面,作为一个非经典光源,单光子源可以用来演示量子力学的基本原理,展现量子物理的奇异性。另一方面,基于量子力学的量子信息技术也需要利用单光子源来实现量子保密通信和量子计算。因此,对实用、可靠的单光子源的制备、测量和操控已经成为当前量子物理学最前沿的研究内容之一。利用单量子体系产生单光子是制备单光子源的有效手段之一,我们研究了光场激发单分子单光子源,在利用单光子调制光谱研究单分子系统动力学过程中,发现了许多新奇的实验现象。在此基础上对激发光场进行强度调制,实现对单分子荧光光子的强度调制,利用锁相放大器解调后的模拟信号消除了分子荧光辐射起伏、光子计数的量子涨落,实现高清晰度的单SR分子荧光成像,给出一种有效提高信噪比的单分子荧光成像方法。利用光子计数调制的方法测量了DiD分子的荧光寿命,研究了外加电场对分子荧光强度的操控。到目前为止,还没有理想的单光子源达到商业应用状态,现有的研究中大多采用衰减相干光模拟单光子源,在这种准单光子源的测量中,灵敏度、信噪比等关键技术问题一直是很大的困扰。我们利用单光子调制光谱技术和锁相放大技术,明显改善了单光子探测器的探测效率,消除了量子涨落的影响,提高微弱信号检测中的信噪比。本论文工作的创新点：1.提出了一种可靠的单光子调制的方法,将相干光衰减至单光子量级,提高了1.55微米InGaAs单光子雪崩光电二极管的探测效率,抑制了探测背景噪声。通过对较低的甄别电压进行优化,利用单光子调制的方法可将在1.55微米波长的探测效率比传统的光子计数方法提高1.87倍。增加了在高背景噪声场合下进行高灵敏探测的可能性,这种灵敏测量可以扩展到其他波长的单光子有效检测。2.测量单光子调制吸收光谱。将1.5微米分布反馈半导体激光器的输出光衰减至单光子量级,测量得到乙炔气体v1+v3带P5e支的单光子吸收光峰。这种单光子波长高频调制吸收光谱消除了低频段较高背景的噪声,通过探测乙炔气体的单光子吸收光谱,对离散的单光子响应脉冲进行锁定放大,获得信噪比为51的激光器频率锁定的鉴频曲线,稳频后的激光在175s内频率起伏小于25MHz。3.无量子涨落的单分子荧光成像,利用声光调制器对激发光场进行强度调制,实现了对单分子荧光光子的强度调制,通过锁相放大器解调,使得只包含荧光信号的调制谐波信号成分得到了放大,其它频率的背景信号被明显抑制,显著提高了光谱成像信号的信噪比,将量子涨落由1/3压制到了1/15,实现了高清晰度的单分子荧光成像。4.单光子源的外场操控,测量了系综分子和DiD分子的荧光寿命,并研究了外加电流对荧光寿命的影响,研究发现在电流作用下,分子荧光平均寿命减小大约20%。利用外电场调制单SR分子荧光强度,实现了单分子荧光强度的外场调控。更多还原

【Abstract】 Quantum information technology is one of the most attractive frontiers, emerging interdisciplinary in recent years, involving many disciplines. For centuries, physicists have been trying to understand the nature of light. Single-photon generation, detection and manipulation as a strong technology supported several interesting photophysical new areas.Due to the wide range of applications of quantum information, the single photon sources have attracted great interest. On the one hand, as non classical light sources, single photon sources can be used to demonstrate the quantum mechanics basic principles, to show the singularity of quantum physics. On the other hand, quantum information technology also need to use the single-photon sources for quantum cryptography and quantum computing based on quantum mechanics,. Therefore, the preparation, measurement and manipulation of practical and reliable single-photon sources have become one of the forefront researches in quantum physics. Single photon prepared from a single quantum system is an effective means of single-photon source; we study single photon sources by light field excited single-molecule. Single-molecule system dynamics was studied by single photon modulation spectroscopy, we found many novel experimental phenomena. On this basis, the single molecule fluorescence photon intensity modulation achieved by lock-in amplifier and eliminated the quantum fluctuations of the molecular fluorescence radiation fluctuations. The high definition imaging for single SR molecule fluorescence gives an effective single molecule fluorescence imaging methods with hign signal to noise ratio. The fluorescence lifetime of the DiD molecule was measured by photon counting modulation, Manipulation the molecular fluorescence intensity by the electric field.So far, no ideal single photon source to the commercial application, usually, the weak coherent light were used to simulate the single photon source in most studies. The measurement of single-photon sources, including the sensitivity, signal to noise ratio and other key technologiesthe problem were a great distress. Single photon modulation spectroscopy and lock-in amplifier technology improved the detection efficiency of single photon detectors, significantly. The influence of quantum fluctuations was eliminated and the signal to noise ratio of weak signal detection was improved.The innovations of this paper:1. A reliable single-photon modulation technology was proposed, improved the detector efficiency of1.55μm InGaAs single photon avalanche photodiode, and restrained the background noise. The detection effiency of1.55μm wavelength can be increased1.87times than the traditional photon counting method by optimizing the threshold voltage of the detector using single photon locked technology. The possibility of highly sensitive detection in high background noise was improved; such sensitive measurements can be extended to other wavelengths of single photon detection.2. Measure the single-photon modulation spectroscopy. Single photon absorption peak of acetylene gas was measured by1.5-micron distributed feedback semiconductor laser. The high-frequency modulation of single-photon wavelength absorption spectra eliminates the background noise in low frequency. The error signal was obtained by Single-photon absorption spectroscopy of acetylene gas, the laser frequency stabilization in the175s frequency fluctuation less than25MHz.3. Single molecule fluorescence imaging without quantum fluctuations. The single-molecule fluorescence photon intensity modulation was achieved the intensity modulation of the excitation light field using acousto-optic modulator. The logic pulse signal output from single-photon detector was demodulated by lock-in amplifier. The background signal of other frequency was significantly inhibited, significantly. The signal to noise ratio of spectral imaging was improved, suppressed the quantum fluctuations from1/3to1/15, to achieve a high-resolution single-molecule fluorescence imaging, and achieved the high-definition single-molecule fluorescence imaging.4. External manipulation of single-photon source, measuring the fluorescence lifetime of the ensemble molecules and DiD molecules, studied the influence of impressed current on the fluorescence lifetime, the study found the average molecular fluorescence lifetime reduced about20%by current. The single-molecule fluorescence intensity control was achieved by external electric field modulation of single SR molecule fluorescence intensity.更多还原