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“全光子量子中继器”为未来的量子互联网奠定基础

  工程研究人员已经证明了一种可以作为未来量子互联网中坚力量的设备的原理证明。多伦多大学(University of Toronto)工程学教授卢海光(ho - kwong Lo)及其合作者开发了一种全光子量子中继器关键元件的原型,这是长距离量子通信中的关键一步。
  量子互联网是量子信息处理的“圣杯”,它使包括信息理论安全通信在内的许多新应用成为可能。今天的互联网并不是专门为安全而设计的,它表明:黑客、入侵和计算机间谍是常见的挑战。邪恶的黑客不断地在个人、公司和政府建立的复杂防御体系中戳出漏洞。
  有鉴于此,研究人员提出了其他传输数据的方法,这些方法将利用量子物理的关键特性,提供几乎不可破解的加密。最有前途的技术之一涉及量子密钥分发(QKD)技术。QKD利用的事实是,简单的感知或测量量子系统状态的行为会干扰该系统。正因为如此,任何第三方窃听都会留下明显可检测到的痕迹,在任何敏感信息丢失之前,通信都可以中止。
  到目前为止,这种类型的量子安全已经在小规模系统中得到了证明。罗和他的团队是世界各地的一群研究人员中的一员,他们正在为未来的量子互联网奠定基础,他们致力于解决利用光纤通信远距离传输量子信息的一些挑战。
  因为光信号在经过光纤电缆的长距离传输时会失去效力,所以在线路上每隔一段时间就会插入一种称为中继器的装置。这些中继器增强和放大信号,以帮助沿线路传输信息。
  但是量子信息是不同的,现有的量子信息中继器存在很大的问题。它们需要在中继器站点存储量子态,这使得中继器更容易出错,难于构建,而且非常昂贵,因为它们通常在低温下运行。
  罗和他的团队提出了一种不同的方法。他们正在开发下一代的中继器,称为全光子量子中继器,它将消除或减少标准量子中继器的许多缺点。在大阪大学、富山大学和日本NTT公司的合作下,Lo和他的团队在最近发表在《自然通讯》上的一篇论文中证明了他们的工作理念。
  “我们已经开发了全光子中继器,允许时间反转自适应钟形测量,”Lo说。因为这些中继器是全光的,它们提供了传统的基于量子记忆的物质中继器所没有的优势。例如,这种方法可以在室温下工作。
  量子互联网可以提供在传统互联网上无法实现的应用,比如不可穿透的安全性和量子隐形传态。
  罗说:“全光网络是一种很有前途的基础设施形式,可用于未来量子互联网所需的快速、高效的通信。”“我们的工作为未来铺平了道路。”

英文版(原文)
All-photonic quantum repeaters could lead to a faster, more secure global quantum internet

Engineering researchers have demonstrated proof-of-principle for a device that could serve as the backbone of a future quantum Internet. University of Toronto Engineering professor Hoi-Kwong Lo and his collaborators have developed a prototype for a key element for all-photonic quantum repeaters, a critical step in long-distance quantum communication.
A quantum Internet is the 'Holy Grail' of quantum information processing, enabling many novel applications including information-theoretic secure communication. Today's Internet was not specifically designed for security, and it shows: hacking, break-ins and computer espionage are common challenges. Nefarious hackers are constantly poking holes in sophisticated layers of defence erected by individuals, corporations and governments.
In light of this, researchers have proposed other ways of transmitting data that would leverage key features of quantum physics to provide virtually unbreakable encryption. One of the most promising technologies involves a technique known as quantum key distribution (QKD). QKD exploits the fact that the simple act of sensing or measuring the state of a quantum system disturbs that system. Because of this, any third-party eavesdropping would leave behind a clearly detectable trace, and the communication can be aborted before any sensitive information is lost.
Until now, this type of quantum security has been demonstrated in small-scale systems. Lo and his team are among a group of researchers around the world who are laying the groundwork for a future quantum Internet by working to address some of the challenges in transmitting quantum information over great distances, using optical fibre communication.
Because light signals lose potency as they travel long distances through fibre-optic cables, devices called repeaters are inserted at regular intervals along the line. These repeaters boost and amplify the signals to help transmit the information along the line.
But quantum information is different, and existing repeaters for quantum information are highly problematic. They require storage of the quantum state at the repeater sites, making the repeaters much more error prone, difficult to build, and very expensive because they often operate at cryogenic temperatures.
Lo and his team have proposed a different approach. They are working on the development of the next generation of repeaters, called all-photonic quantum repeaters, that would eliminate or reduce many of the shortcomings of standard quantum repeaters. With collaborators at Osaka University, Toyama University and NTT Corporation in Japan, Lo and his team have demonstrated proof-of-concept of their work in a paper recently published in Nature Communications.
"We have developed all-photonic repeaters that allow time-reversed adaptive Bell measurement," says Lo. "Because these repeaters are all-optical, they offer advantages that traditional—quantum-memory-based matter—repeaters do not. For example, this method could work at room temperature."
A quantum Internet could offer applications that are impossible to implement in the conventional Internet, such as impenetrable security and quantum teleportation.
"An all-optical network is a promising form of infrastructure for fast and energy-efficient communication that is required for a future quantum internet," says Lo. "Our work helps pave the way toward this future."

关键词:量子互联网