Researchers at Toshiba design quantum network for secure communications

Sep 05, 2013 by Bob Yirka report
Downstream and upstream quantum access network. a, In a downstream configuration the quantum transmitter is positioned at the network node. The transmitted quantum key is randomly directed to one of the quantum receivers by a passive optical splitter. Each user needs a single-photon detector, and the key is not distributed deterministically. b, The upstream configuration requires only a single detector at the network node. The quantum transmitters share this detector by ensuring that only photons from one transmitter at a time reach the receiver. Credit: Nature 501, 69–72 (05 September 2013) doi:10.1038/nature12493

( —A team of researchers at Toshiba Corporation has developed technology that allows up to 64 users to participate in a quantum key distribution (QKD) network with another single user. In their paper published in the journal Nature, the team describes how they built their network and how it might be used.

Scientists have known for years that conventional would become vulnerable as computers grew bigger, faster and more powerful. For that reason, researchers in the field have turned to QKD schemes because the say that it's impossible for such keys to be used without them being disturbed in the process. That would make them the perfect encryption scheme. Unfortunately, to date, virtually all such systems that have been built are point-to-point and only work in topographies. In this new effort, the researchers at Toshiba describe a way to allow a single transmitter to send quantum keys to 64 end users—in essence, creating a quantum key based network.

Quantum keys are based on polarized —by stringing them together in a series. But because they are photon based, they are extremely sensitive to noise. For this reason, that use them allow just a single node to communicate directly with just one other node—using very expensive transmitters and receivers on both ends. Making things even more difficult is that the lines that carry the data have to travel in a straight line. These two constraints have severely limited the ways in which the technology can be used. To date, other attempts to use quantum keys in a network have been mesh based, which means every node still only is able to send a key to one other single other node and vice-versa. To get around this problem the engineers at Toshiba built a hub device (with an expensive receiver) that could be shared by as many as 64 other people, allowing all 64 to send and receive with one other node outside of the hub. They achieved this feat by employing two types of quantum transmitters that are able to operate at variable repetition rates along with stabilization components.

The researchers report that their approach is scalable and is constrained only by the power and speed of the transmitters and receivers. Thus it's conceivable that their approach could eventually be applied to much larger networks leading to widespread use of QKD in a variety of applications.

Explore further: Quantum computer emulated by a classical system

More information: A quantum access network, Nature 501, 69–72 (05 September 2013) DOI: 10.1038/nature12493

The theoretically proven security of quantum key distribution (QKD) could revolutionize the way in which information exchange is protected in the future1, 2. Several field tests of QKD have proven it to be a reliable technology for cryptographic key exchange and have demonstrated nodal networks of point-to-point links3, 4, 5. However, until now no convincing answer has been given to the question of how to extend the scope of QKD beyond niche applications in dedicated high security networks. Here we introduce and experimentally demonstrate the concept of a 'quantum access network': based on simple and cost-effective telecommunication technologies, the scheme can greatly expand the number of users in quantum networks and therefore vastly broaden their appeal. We show that a high-speed single-photon detector positioned at a network node can be shared between up to 64 users for exchanging secret keys with the node, thereby significantly reducing the hardware requirements for each user added to the network. This point-to-multipoint architecture removes one of the main obstacles restricting the widespread application of QKD. It presents a viable method for realizing multi-user QKD networks with efficient use of resources, and brings QKD closer to becoming a widespread technology.

Related Stories

Researchers test quantum encryption hacking risk

May 28, 2013

( —Quantum communication systems offer the promise of virtually unbreakable encryption. Unlike classical encryption, which is used to send secure data over networks today and whose security depends ...

Recommended for you

Physicists solve quantum tunneling mystery

16 hours ago

An international team of scientists studying ultrafast physics have solved a mystery of quantum mechanics, and found that quantum tunneling is an instantaneous process.

How spacetime is built by quantum entanglement

16 hours ago

A collaboration of physicists and a mathematician has made a significant step toward unifying general relativity and quantum mechanics by explaining how spacetime emerges from quantum entanglement in a more ...

Experiment confirms quantum theory weirdness

16 hours ago

The bizarre nature of reality as laid out by quantum theory has survived another test, with scientists performing a famous experiment and proving that reality does not exist until it is measured.

Quantum computer emulated by a classical system

17 hours ago

(—Quantum computers are inherently different from their classical counterparts because they involve quantum phenomena, such as superposition and entanglement, which do not exist in classical digital ...

Squeezed quantum cats

May 26, 2015

ETH professor Jonathan Home and his colleagues reach deep into their bag of tricks to create so-called 'squeezed Schrödinger cats.' These quantum systems could be extremely useful for future technologies.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.