If it is ever possible to create an ultra-secure, super-fast 'quantum internet', then quantum entangled photons are absolutely essential for it – and scientists have just found a very useful new way to generate them.
Quantum entanglement is a phenomenon where two particles (like photons) are linked to each other, regardless of the physical distance between them. If something happens to one of the particles, something must happen to the other.
Although physicists still do not fully understand exactly how entanglement occurs, this phenomenon opens up the possibility of long-range communication with quantum power – where shifts in particles in one place lead to shifts in entangled particles over huge distances.
This particular study suggests that quantum entangled photons are being used as quantum key distribution (QKD), a kind of low-level quantum Internet, where classical data in the form of ones and zeros gain an extra layer of privacy and security through quantum physics.
Until now, the entangled photons used for these encryption methods have been limited to the near infrared wavelength range of 700 to 1550 nm, making them vulnerable to interference from light-absorbing gases and solar radiation.
In other words, the data connection only works at night: not ideal for what is supposedly next generation internet infrastructure.
New research shows how to generate and detect entangled photons at a longer wavelength of 2.1 micrometers that is shielded from such interference. The end result is a much more reliable and stable communication channel.
“We have demonstrated that polarization-entangled pairs of photons can be generated, controlled and detected using our approach,” the researchers write in their published paper.
“This work provides a new platform for quantum optics and paves the way for technology applications for quantum sensing and long-range quantum secure communications in this wavelength mode.”
To achieve this, the researchers used a nonlinear lithium niobate crystal: entangled pairs of photons were created using ultra-short pulses of light from a laser aimed at the crystal.
The Quantum Internet, if we can figure out how to create it, promises to be many times more powerful, more secure, and more private than anything we have today. For example, any hacking attempt would instantly sever the corresponding connection – a good security net.
We are still a long way from realizing this dream – at a distance, in stability, in practicality – but innovations like these are steadily bringing us closer and transforming quantum computing from hypothesis into reality.
“The next important step will be to miniaturize this system by converting it into integrated photonic devices, making it suitable for mass production and for use in other applied scenarios,” says quantum physicist Michael Kues of the University of Hannover. Leibniz in Germany.
The study was published in the journal Science Advances.
