The word “quantum” often brings to mind the almost impossible; quantum physics, quantum theory, quantum mechanics – all dizzying topics understood by few.

For those of us currently without a doctorate in physics, the idea of quantum technology sounds very much like science fiction.
However, it’s very much scientific fact and boffins at Toshiba Research Europe have made a breakthrough that could see quantum technology implemented in the fight against cyber crime and hacking. Using Toshiba’s Quantum Access Network, quantum cryptography could be commercially viable. But how does it work?

“It’s a way of securing communications on fibre-optic networks,” Dr Andrew Shields, head of the research programme told Computing.
“It’s very different from the prevailing technology at the minute, and it’s very useful for sending for digital encryption keys along the fibre in a way we can test whether or not those keys are secret.”
Shields added the very nature of quantum cryptography means the method is ideal for keeping digitally encrypted files secure.
“The technology is based on sending each bit for those keys encoded on a single photon – a particle of light – because quantum physics tells us if someone tries to measure a single photon, that changes their encoding and that can be sensed by the system,” he said.
Harnessing quantum cryptography for mainstream use hasn’t been possible before, with each user requiring an elaborate – and expensive – photon detector to connect to the quantum network. Toshiba’s breakthrough means that it could be possible for up to 64 users to connect to a single detector in a Quantum Access Network, significantly increasing the technology’s potential reach.
“In the past this technology has been used for point to point links between two users, usually called Alice and Bob for A to B, Alice sends the single photons and Bob detects them,” Shields explained.
“But what we’ve shown is that you can make a point to multi-point link, so we can connect multiple senders, or multiple Alices up to a single Bob, and allow them to share a fibre and share a photon detector, which is the expensive part of the network.
“That’ll make the cost of a quantum network cheaper for each user in the future and allow us to build networks with many more users than has been possible in the past,” he said.
In essence, Shields added, it means the high-level security offered by Quantum Access Networks could become up to 64 times cheaper than it is now.
“We can combine the signals of 64 different users onto a single fibre, so the cost will be shared between 64 people rather than by a single user,” he said.
“We can think about networks which now are 64 times larger, or 64 times cheaper per person, or at least that order of magnitude, so really it’s a significant change.”
Traditionally, the technology has only been used for networks that need maximum security, such as those employed by governments or financial institutions, but Shields told Computing that Toshiba’s breakthrough could see its use become much more widespread.
“If we can make the technology more widely available, and cheaper, then it could have far wider applications – even general business use.”
Shields admitted that quantum networking still remains costly, but hopes by allowing more users to connect to a single fibre, the demand will eventually drive the costs of installing such technology down.
“Like many new areas of technology it’s a question of cost. So initially the cost is very high and it’s used in certain niche applications, but then as the cost comes down it becomes more attractive for more mainstream applications,” he said.
“So that’s what we’re trying to do with innovation, we’re allowing many users to share the cost of a fibre quantum network, that’s really the advantage of this technology.”
Toshiba’s quantum cryptography breakthrough sounds good on paper, but enterprises will only be able to reap the benefits when quantum access networks are readily available.

While Toshiba has no firm date for when it will actually release the technology, Shields told Computing that in his opinion, wider uses of quantum cryptology could be a reality in the not-to-distant future.
“I could imagine that at least the technology for a quantum access network will be ready in three to five years,” he said.
@DannyJPalmer

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