Generation of non-classical electromagnetic field by a coherent conductor / Génération de champ électromagnétique non classique par un conducteur cohérent

微电子工业的进步使亚微米尺寸的元件的制造成为可能。已经进行了许多实验来测量这种纳米结构中的平均电流。更微妙，但更困难的是测量电流的波动，通常被称为“噪音”。电子在低温下在小导体中的行为不能用通常的物理定律来解释，在室温下的宏观世界中是有效的：相反，人们必须引用量子力学来理解这种条件下的电学定律。不仅电流如此，噪声也是如此。然而，噪声，波动的电压和电流，只不过是波动的电磁场，即光。这里考虑的是微波域和电路中的噪声，而光通常与更高的频率和自由空间中的传播有关，但它们是相同的。而量子力学应用于光是物理学的一个分支，叫做量子光学。 这项研究计划的目标正是探索和利用导体中的电子可以产生什么样的量子光信号。特别是，可以应用我们的纳米结构中的量子电子输运的知识，以产生微波辐射的量子特性有用的信息处理？虽然人们付出了巨大的努力，利用量子光学的通常原理来设计量子辐射，例如应用于超导体，但人们是否可以利用普通金属或半导体中的量子电子学原理来实现类似的目标？ 本研究计划将探讨三个主要方向： 1)光的非高斯态的产生，以量子信息处理的资源而闻名。在宏观样品中，大多数随机现象都由高斯定律描述。在量子导体中不是。它是如何影响辐射的？ 2)反馈是一种无处不在的工程技术，它包括测量系统并使用测量结果来对系统做出反应，以便控制其行为。我们能通过反馈来增强噪声的量子特性吗？ 3)当温度接近系统的相关能量标度（例如超导体中的差距）时，量子方面减弱。在正常导体中，这种能量尺度是巨大的，因此应该能够在相对较高的温度下产生非常高频率的量子信号。为此，将设计新的源和探测器。

Progress in the industry of micro-electronics have made possible the fabrication of components of submicron size. Many experiments have been performed to measure the average current in such nanostructures. More subtle, but much more difficult are the measurements of the fluctuations of the current, usually nicknamed “noise”. The behavior of electrons in small conductors at low temperature cannot be explained by usual laws of physics, valid in the macroscopic world at room temperature: instead, one has to invoke quantum mechanics to understand laws of electricity in such conditions. This is true not only for the current but also for the noise. However the noise, fluctuating voltage and current, is nothing but a fluctuating electromagnetic field, i.e. light. Noise is here considered in the microwave domain and in circuits, while light is usually associated with much higher frequencies and propagation in free space, but they are the same. And quantum mechanics applied to light is a branch of physics, called quantum optics. The goal of this research program is precisely to explore and harness what kind of quantum optical signals can be generated by electrons in conductors. In particular, can one apply our knowledge of quantum electronic transport in nanostructures to the generation of microwave radiation with quantum properties useful for the processing of information ? While there is a huge effort to engineer quantum radiation using the usual principles of quantum optics, applied for example to superconductors, can one use the principles of quantum electronics in normal metals or semiconductors to achieve similar goals ? Three main directions will be explored in this research program: 1) the generation of non-Gaussian states of light, known for being resources for quantum information processing. In a macroscopic sample, most random phenomena are described by the Gauss law. Not in quantum conductors. How does that imprint on the emitted radiation ? 2) feedback is an ubiquitous engineering technique that consist of measuring a system and use the result of the measurement to react on the system, in order to steer its behavior. Can one enhance the quantum character of noise by feedback ? 3) quantum aspects fade when the temperature approaches the relevant energy scale of a system, such as the gap in superconductors. In normal conductors, this energy scale is huge, so one should be able to generate quantum signals of very high frequency at relatively high temperature. For this, novel sources and detectors will be designed.