【作者】 王涛；

【导师】 苏雪梅；

【作者基本信息】 吉林大学 ， 光学， 2017， 博士

【摘要】 量子关联虽然导致量子态的各种创新的应用,但是也对环境噪音的反应非常敏感。在常规的量子信息处理和各种量子技术中,量子态的制备需要隔绝外界的噪音。虽然在这个方向上的努力已经导致了单粒子或少粒子量子态的精确制备和控制,但是对于复杂的量子系统的制备和控制依然困难。在这种主流的研究思路之外,两种非常规的量子态制备和量子信息处理方式在最近的十年内开始得到更多人的关注。一是耗散控制设计的观念,一是弱作用过程的研究。耗散控制设计考虑把系统外的环境也看作一种资源,用来设计稳定的量子态。虽然有噪音的影响,我们依然可以通过耗散通路的设计,获得纯的纠缠态和具有高度量子关联的量子态。这些年,这个领域的基本想法和关键机制已经被广泛的讨论,并且取得了显著的成功。在弱作用过程下,作用的时间短暂,作用的强度非常弱,导致量子态的变化也非常小,但是也使得耗散过程可以被忽略,使得制备的量子态纯度很高。一种弱作用过程加后选择的想法最近得到了很多关注,称为后选择弱测量。这种观念可以看成是在传统的标准测量方案的基础上加上后选择。但是到了今天,这种观念已经突破了测量的范畴,成为量子态制备和精密测量的一个重要方案。在本论文中,我们对耗散控制设计在光力学系统中的应用做了非常有意义的探讨,我们利用腔和遂穿诱导透明设计了两种性能良好的量子器件,并且对热态的后选择问题做了开创性的研究。通过这些研究,可以看出耗散控制设计和后选择弱测量尤其非常独特的量子系统制备和控制的优点。光力学系统已经成为了实验量子光学领域的一个热点领域,也激发了许多原创性的理论研究。由于力学振子系统是一个宏观系统,所以它所能产生的量子关联对于我们理解各种量子基础问题尤为重要。在光力学系统中产生纠缠甚至强纠缠引起了很多人的关注。在本文中,我们用耗散控制设计的观念讨论了一个四模光力学系统的稳态纠缠问题。基于以前的文章中讨论问题的思路,我们首次把耗散控制设计的思想用到常温下的光力系统。在已有的工作中,光力学系统的两体纠缠的对数负性在零温时小于0.7,在常温时根本没有。王颖丹等人的工作给出产生强纠缠的方法,但是他们的工作是在零温下讨论的。我们发现,该系统在常温下也可以获得显著的纠缠,这与以前的光力学纠缠的工作是非常不同的。而且纠缠随着温度升高的变化方式也和以前的研究区别很大。同时,这个系统也是量子力学无关子空间的一个典型案例。随后我们利用同样的四模光力学系统讨论了不同波长的相干光转移的问题。在不同的频率光之间转移信息是量子网络中的基本问题。在现有的方案中,基于光力学系统的量子态转移如果要获得高的转换效率,需要两个目标腔模的驱动光的强度较大,同时也要求两个腔模的耗散几乎相等。这一方面不利于调控,过强的驱动光会导致力学振子的加热,破坏转换效率,另一方面对于两个腔的设计要求较高。我们首次提出了蓝带边驱动的耗散控制设计的想法。虽然多了一个控制模式,却可以使得相干光转移的耦合强度极大的降低,并且两个目标腔的耗散可以非常不同。尤为重要的,在这里我们揭示了模式消除的想法,可以用到许多其他的量子控制问题中。腔既可以增大也可以减少量子系统的耗散,同时可以极大的增强光与量子系统的耦合强度。而隧穿诱导透明就是设计一个共同的耗散通道,使得两个临近的量子态模式发生干涉,导致透明现象。在本文中,我们同时用这两种方法设计了两种量子器件,都是作用于中红外区的,一种可以延迟光传播的时间,另一种可以对两种频率的光进行开关控制。这两种设计都已经申请专利。后选择弱测量从一出现就引起了广泛的争议,但是其独特的弱作用反常放大能力得到了认可,并且被广泛研究。在现有的工作中,利用后选择弱测量来放大克尔介质中的单光子非线性,这个想法最近得到了极大的发展。但是在现有的工作中,他们只是讨论了相干光作为探针的现象。在我们的工作中,我们用一个热态指针来探究单光子交叉克尔效应,做了非常详细的讨论,我们发现热态指针和相干光指针的放大现象非常不同,热态指针的放大效果更加显著。我们把弱效应推广到热态指针诱导的强效应上。我们发现,对于强效应,传统弱值解释是不成立的。同时,我们也给出了后选择诱导的缩小效应和大概率的放大现象。这些结论都超出了以前的研究范围。热光交叉克尔效应进一步揭示出后选择弱放大的虚放大效应是一种纯粹的经典效应,并且和最近的平衡弱测量技术结合起来,我们给出了虚放大的一般机制。更多还原

【Abstract】 Although the quantum correlations boost various innovative applications of quantum states,it is very sensitive to any noise from environment.In usual protocols in quantum information processing and quantum technology,it is necessary for preparation of quantum state to be isolated from environmental noises.Although this endeavor has created many techniques to precisely prepare and control the quantum state of single particles or few particles,it is still difficult to deal with complex quantum systems of multi-particles.Beyond the major schemes,two unusal approaches has attracted much attention to prepare the quantum state in quantum information processing in the past decade.One is involved in reservoir engineering,and the other is about dynamics of weak interaction.Reservoir engineering regards the environments of the quantum system as resources to create a stationary state.Althrough the noise still takes effect,pure entanglement state or states with hight quantum correlations can be obtained with special choosen dissipation channel.In this field,many schemes and basic mechanisms have been fully discussed and experimentally verified.For weak interaction,the interaction time is very short,and the interaction strength is very weak,which makes quantum evolution changed very small.Thus dissipation in this weak process can be also omitted and high pure quantum state can be prepared.Recently,the idea combining the weak interaction and postselection attracts much attenstion.This is usually called postselection weak measurement.This scheme can be taken as implement of the standerd measurement in postselection of the quantum state.However,up to now,this perspective has beyond a measurement scheme to play an important role in preparation of a quantum state and to do precisemetrology.Quantum optomechanics has been a hot topic in experimental quantum optics,which stimulates many creative theoretical researches.For the mechanical oscillator in a macroscopic object,the quantum correlations introduced by it is vital to our understanding on the quantum fundamental problems.A major problem in this field is how to effectively create entanglement or even strong entanglement.Based on the existing work,we firstly use the idea of dissipative engineering to dicuss entanglement in a four-mode optomechanical system at room temperature.In the past,it is widely accepted that the entanglement between two boson modes is below 0.7,and there is none entanglement at room temperature.However,Yingdan Wang et al provided new method to generate strong entanglement.They care about situation at zero degree Kelvin but don’t discuss that at room temperature.We find that prominent entanglement can also exist at room-temperature,which can not be found before.Meanwhile this system is also a typical example without subspaces of quantummechanics.In the following,we discuss with issues of the conherent state coversion between two fields with different frequencies based on the same four-mode setup.Converting informations between different fields is a basic problem in quantum networks.In the existing scheme,if high conversion efficiency is expected,the driving strengths between two cavity modes and the two driving modes must be large enough and the losses of the two target cavities are nearly the same.However,on one hand,too large intensities of driving lights are against controlling and thus easily induce the mechanical oscillator hot,and degrade the conversion effiency.On the other hand,the qualitiy designing for the two cavites needs to be high.We proposed and analysised the idea of driving the cavity mode at blue-detuned sideband for the first time.We demonstrated that the optomechanical cooperativity can be greatly decreased and losses of the two target modes can be different.We revealed a simple mode-removing method,which can be very useful for other quantum controlling problems.In my work using semiconductor microcavity,cavity can be used to reduce thedissipation of the quantum system,and can also greatly increase the coupling strength between light fields and the quantum system.A common dissipation channel is utilized to create tunnelling induced transperancy and to interfere two adjacent quantum states,inducing transperancy.In this thesis,two quantum devices based on this microcavity system is discussed at the intermediate infrared region for lights.One can be used to postpone the propagating time,and another can used to control two color lights simultaneously.From its apperence,postselection weak measurement has caused a lot of controvers.Using this idea to amplify the single-photon cross-Kerr nonlinearity,its unexpected amplification effect has been confirmed by many experiments.Different form much existing work,that only coherent light is used to do as the probe,we study the single-photon cross-Kerr effect using a thermal light as a meter.We find the results using thermal light cross-Kerr effect different from that induced by the coherent light.We disuss the strong effect induced by the thermal meter itself,which is beyond the traditional opinions.We find the weak value is not useful to explain the strong effects.Furthermore we present the postseletion induced reduction and large probability amplification.Thermal light cross-Kerr effect also reveals that the imaginary amplification is a pure classical effect,and we give the general dynamics for it based on the balanced weak measurement.更多还原