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Weak measurements of quantum effects in electronic nano-devices

电子纳米器件中量子效应的弱测量

基本信息

批准号：
243616108
负责人：
Dr. Alessandro Romito
金额：
--
依托单位：
Department of Physics
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/243616108?language=en
关键词：
Weak measurements quantum effects electronic

项目摘要

The measurement process is a key aspect of the actual control and manipulation of nano-size solid state systems. A description of such a process beyond the standard projection postulate is generally needed in solid state nano-devices. The measurement can then be described as a continuous acquisition of information by the detector alongside a gradual modification of the system's state, allowing for a weak regime with parametrically small back-action. A remarkable consequence appears in the case of quantum conditional measurements where the outcome of a weak measurement, conditional to a subsequent strong one (postselection), leads to the so-called weak value (WV). WVs substantially differ from standard ones and, uniquely due to the quantum correlations between the two measurements, can be negative whereas the standard outcome is positive. WVs have been experimentally observed in optical systems. They have been used in addressing fundamental problems in quantum mechanics and employed for precision measurements and classical signal amplification in optics. Related proposals exist for solid state systems as well. The potential of weak measurements and WVs in detecting quantum processes without essentially disturbing them has however not yet been exploited to get insights into systems where standard strong measurements would fail.This proposal is aimed at advancing the concept of weak measurement in this direction. It will focus on electronic nano-devices which, despite being more demanding for experimental realizations, naturally present coherent quantum dynamics and many-body effects not directly detectable by strong measurements (which would instead destroy them). Here, weak values, with their soft back-action, might uniquely provide new physical insight. The proposal will address specific cases, which might trigger experiments in the field. As a first step we will consider the weak detection of ``virtual'' cotunneling electrons and use the WV protocol to define the cotunneling time. Along the same line we will also consider the weak detection of quantum adiabatic processes, and driven quantum systems. In the latter, WVs can offer a viable way to the definition of work at a quantum level, also for systems in contact with an environment. Beyond that, as a further possible step in the project, we plan to possibly advance the concept of weak measurement to the detection of topological excitations, and their braiding, considering the specific case of Majorana end-states in 1D superconducting wires.

测量过程是纳米尺寸固态系统的实际控制和操纵的关键方面。在固态纳米器件中，通常需要对超出标准投影假设的这种过程进行描述。然后，测量可以被描述为通过检测器连续获取信息，同时逐渐修改系统的状态，从而允许具有参数小反作用的弱状态。一个显著的结果出现在量子条件测量的情况下，其中弱测量的结果，以随后的强测量（后选择）为条件，导致所谓的弱值（WV）。WVs与标准WVs有很大不同，并且由于两个测量之间的量子相关性，WVs可以是负的，而标准结果是正的。WVs已经在光学系统中被实验观察到。它们已被用于解决量子力学中的基本问题，并用于光学中的精密测量和经典信号放大。对于固态系统也存在相关的建议。然而，弱测量和WVs在检测量子过程而不干扰它们的潜力还没有被利用来深入了解标准强测量会失败的系统。它将专注于电子纳米器件，尽管对实验实现的要求更高，但自然呈现出相干量子动力学和强测量无法直接检测到的多体效应（这反而会破坏它们）。在这里，弱值及其软反作用可能会独特地提供新的物理见解。该提案将涉及可能引发实地试验的具体案例。作为第一步，我们将考虑“虚拟”共隧穿电子的弱检测，并使用WV协议来定义共隧穿时间。沿着同样的路线，我们也将考虑量子绝热过程和受驱动量子系统的弱检测。在后者中，WVs可以提供一种可行的方式来定义量子级别的工作，也适用于与环境接触的系统。除此之外，作为该项目的进一步可能步骤，我们计划可能将弱测量的概念推进到拓扑激发及其编织的检测中，考虑到1D超导导线中Majorana端态的具体情况。