Developing interferometers to detect electric field signals with very high sensitivity

该项目是关于开发干涉仪来检测电场信号，具有非常高的灵敏度，超出了经典力学的能力。具体地说，它旨在提高时间分辨红外和太赫兹场测量的灵敏度。在过去的几年里，干涉测量的增强导致了许多领域的基础性发现，这个特殊的项目可以揭示新的革命性的相互作用，帮助我们拓宽现实的范围，更好地理解宇宙的本质。干涉仪的灵敏度可以通过使用纠缠光子或压缩态来提高和克服标准量子极限。这确实是过去30年研究的突破之一。Carlton Caves的开创性工作：《干涉仪中的量子力学噪声》发表在《物理评论D》，23,1693(1981)上，描述了这种可能性的最显著的例子之一。我们目前仅限于可见光和近红外频率，这个项目将关于使用这些量子态来增加低频辐射的灵敏度，在光谱的红外和THZ部分。除了潜在的相关技术成果外，深入研究这一频谱中基本上未被探索的部分将带来令人兴奋的研究挑战。在太赫兹频率下，可以观察到不寻常的光与物质的相互作用，例如载流子的非微扰效应，这补充了一些有趣的应用，包括安全和质量控制。该项目的目标是利用光的量子态来提高红外和太赫兹探测器的灵敏度。将被研究的红外传感的主要方法是时间域光谱学。这是一种探测技术，涉及几十飞秒量级的短激光脉冲，由于某些非线性晶体中发生的称为电光效应的非线性过程，这些脉冲及时对未知的红外辐射进行采样。关于这项技术的详细描述可以在张晓春和徐景洲(Springer 2009)的《太赫兹波光子学导论》中找到。更多最新的研究论文将补充这一背景。该项目旨在通过应用最近发展的量子计量技术来改进这一方法。理解为什么量子态可以帮助提高测量的灵敏度的起点在几本教科书中有描述，例如G.Grynberg，A.Aspect和C.Fabre(剑桥大学出版社，2010)的《量子光学导论》。从本质上讲，时域光谱学是一种脉冲干涉仪。为了将其灵敏度提高到标准量子极限以上，将按照最初的Caves的建议，在干涉仪的开放端口注入压缩态。这种非经典状态可以通过放大飞秒光脉冲泵浦的参数放大器中的真空波动来产生。与此背景相关的非线性光与物质相互作用的参考教科书有J.-C.Diels和W.Rudolph(学术出版社，2006)的《超短激光脉冲现象》和R.Boyd(学术出版社，2008)的《非线性光学》。总体而言，该项目旨在开发新的桌面技术，以提高在飞秒和皮秒时间尺度上发生的效应的灵敏度。发展电子学和纳米工程研究提出的这项技术和推进光子学领域的影响是巨大的，因此，该领域的许多分支课题提供了无数有前途的技术和工业冒险，如果它们取得成果，可能会给现代社会带来革命性的变化。例如，可以研究其他时变效应，如与弱磁场有关的影响，或局部重力的扰动。

The project is about developing interferometers to detect electric field signals with very highsensitivity, beyond that enabled by classical mechanics. Specifically, it aims at increasing thesensitivity of time-resolved infrared and terahertz field measurements.Enhancement of interferometry in the past years has led to fundamental discoveries in numerousfields, and this particular project can reveal new and revolutionary interactions to help uswiden our scope of reality and understand the nature of the universe a little better. The sensitivity ofinterferometers can be boosted and overcome the standard-quantum limits by using entangledphotons or squeezed states. This was indeed one of the breakthroughs of the last 30 years ofresearch. One of the most remarkable examples of this possibility is described in the seminal work of Carlton Caves: "Quantum-mechanical noise in an interferometer" published in Physical Review D, 23,1693 (1981).We are currently limited to visible and near-infrared frequencies, and this project will be about usingthese quantum states to increase the sensitivity of low-frequency radiation, in the infrared and THzpart of the spectrum. Delving into this largely unexplored part of the spectrum will provide excitingresearch challenges, on top of potentially relevant technological outcomes. At terahertz frequency,unusual light-matter interactions can be observed, such as non-perturbative effects of carrierstunnelling, which complements some intriguing applications including security and quality control.The project goal is that of increasing the sensitivity of infrared and THz detectors using quantumstates of light. The primary approach for infrared sensing that will be investigated is known as timedomainspectroscopy. This is a detection technique that involves short laser pulses, in the order offew tens of femtoseconds, which sample in time the unknown infrared radiation thanks to anonlinear process called electro-optical effect that occurs in certain nonlinear crystals. A detailedaccount of this technique can be found in "Introduction to THz Wave Photonics", by X.-C. Zhang andJingzhou Xu (Springer 2009). More up to date research papers will complement this background.The project aims at improving this approach by applying the recently developed quantum metrologytechniques. The starting point to understand why a quantum state can help to improve thesensitivity of a measurement is described in several textbooks, such as "Introduction to QuantumOptics", by G. Grynberg, A. Aspect, and C. Fabre (Cambridge University Press, 2010).The time-domain spectroscopy is, in essence, a pulsed interferometer. To enhance its sensitivityabove the standard quantum limit squeezed states will be injected into the open port of theinterferometer, following the original Caves' proposal. Such nonclassical state can be generated byamplifying the vacuum fluctuations in a parametric amplifier pumped by femtosecond optical pulses.Reference textbooks that are relevant to this background on nonlinear light-matter interaction areUltrashort Laser Pulse Phenomena, by J.-C. Diels and W. Rudolph (Academic Press, 2006) andNonlinear Optics, by R. Boyd (Academic Press, 2008).Overall, the project aims at developing new, table-top technologies to improve the sensitivity ofeffects that occur at the femtosecond and picosecond time scales. The implications of developing Electronics and Nanoscale Engineering Research Proposalthis technology and advancing the field of photonics are massive, and as a result, there are a numberof topics which branch off from this field which provide numerous promising technological andindustrial ventures which could revolutionise modern day society if they were to come to fruition.For instance, other time-varying effects could be investigated, such as those associated with weakmagnetic fields, or perturbations of the local gravity.