微波与光恋爱的媒人


有一句话这么说,世界上最远的距离,是我跟你在一起,向你撒娇,你却在玩手机。当两个恋人的思维不在一个波段时,自然就会鸡同鸭讲,无法继续下去了。打开收音机,调整接收频率,我们可以收听很多个台。同样都是电磁波,不同波段之间可以互相穿过对方,却互不影响。要让不同波段的电磁波“谈恋爱”,我们需要一个“媒人”。电磁波的频率相差越大,越难相互影响,媒人就越难找到。通常用于通信的电磁波,波段距离最远的就是微波与可见光了。如果要让微波与可见光之间谈恋爱,能找到媒人么?答案是能找到,最好的媒人就是光力学系统。

光力学系统是过去几年量子光学领域最火爆的一个题目。一开始,人们的关注点在于如何把其中的宏观机械振子的运动用光冷却到量子基态。正当全世界众多研究机构的科学家们为此通宵达旦的做实验争取第一个达成时,在2010年UCSB的一个研究组另辟蹊径,直接把高频率(6GHz)的振子放置在低温环境(20mK)中,实现了宏观振子的量子基态冷却。最大的桃子被摘掉之后,其他人只好另辟蹊径,寻找光力学系统的应用。

最容易想到的应用就是用它来实现某些非线性光学器件。比如说,光的单向器,非经典光的光源什么的。后来,美国国家标准局的一些科学家想到了,如果我们让一个机械振子与两个不同频率的光同时耦合,是否可以通过振子作为媒介来实现两种光之间的转换呢?他们很快就把这个想法推到极致,干脆我们就研究微波与可见光之间的转换吧。理论分析表明,用机械振子做的频率转换器,效率可以做到接近1,转换过程中,光信号的相干特性也可以得到很好的保持。经过几年的努力,在今年他们终于实现了从微波到可见光的频率转换器。要实现高效且无噪声的转换器,还需要进一步的提高技术指标。

技术的发展可以解决微波与可见光波段不同无法沟通的问题,但是无法解决你需要倾诉时,你的恋人却在玩手机的问题。也许我们需要发明一个通讯器,让人与人的大脑通过无线电波直接交流。可脑电波的频率只有几赫兹,要转换为通讯用的微波频率几兆赫兹,将极为困难。也许光力学系统在这个技术上也能发挥作用?

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3 Comments

  1. “有一句话这么说,世界上最远的距离,是我跟你在一起,向你撒娇,你却在玩手机”

    typical in social science, that is why society need authoritarian politicians, democracy, market system to keep system stable, not falling apart; as witten said, system has to feed 99 potential information carriers with most of them being “fake”, so the “real” information carrier of a very few can emerge.

    in this process, obviously, those system admins of various social scientists such as politicians, wall street, manage the system’s money/fund, often with corruption problems among themselves, these are smart social scientists of various types, few of them if any know nothing about Witten or his theory.

    quantum physics breakthrough in macroscopic world, would help society to progress, much like Newton’s physics getting rid of religion: before newton era, church leaders rules the whole world;

    because of newton physics, politicians or social scientists take the system admin job from church leaders, and largely they rules the world, particularly in developing countries.

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  2. step 1.
    as witten said, system has to feed 99 potential information carriers with most of them being “fake”, so the “real” information carrier of a very few can emerge somehow;

    human social system is a dissipative system, far away from “equilibrium state” of our ideal physics model, and as such, human social system is always in urgent need of new information/energy feed, with which system to survive and grow.

    step 2
    and because the system is often far away from “equilibrium state” of our ideal physics model, we are facing information challenges everyday: what is information and how to “gauge” information?

    the only option is step 1

    and because of that, most information in terms of head counts of those 99 potential information carriers and their output=fake information, mostly noise.

    step 3
    and those social scientists as system admins often make things even worse, not better.

    step 4

    ironically, if system can survive step 1 through step 3, then system has just proven itself, and has therefore grown and progressed.

    I am a social physics modeler, making a lot of comments in your blog, delete them if you want to.

    回复

  3. “在2010年UCSB的一个研究组另辟蹊径,直接把高频率(6GHz)的振子放置在低温环境(20mK)中,实现了宏观振子的量子基态冷却。”

    not sure that is done through “cavity” or “optical dipole”, but in my social physics model, cavity=kind of like GFW, more in developing countries, “optical dipole” and competition among them=democracy/market system, typical case is US.

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