Israeli, German researchers find breakthrough in quantum data security

A new breakthrough in quantum technology brings us closer to secure, efficient quantum computing.

 Conceptual illustration of quantum dots in action. (photo credit: Lars Lüder)
Conceptual illustration of quantum dots in action.
(photo credit: Lars Lüder)

Researchers from the Hebrew University of Jerusalem and the University of Tübingen in Germany have achieved a breakthrough that could provide a device for secure and reliable quantum computing, with the two universities publishing their findings in the peer-reviewed journal ACS Nano.

While quantum computing will revolutionize how we use computers, conducting tasks much faster with less electricity than today's computers, and will also provide tools that will easily crack most of the encryption codes currently used to protect the data we store on computers.

Most computer security available today relies on mathematical manipulations that, while highly effective today, could be easily cracked by a quantum computer. New methods of encryption that rely on the laws of physics will need to be developed to combat this, the researchers explained. 

One such method is to use the quantum properties of single photons (particles of light) to encrypt a message so that any attempt to hack it would be immediately detectable by both the sender and recipient, though getting a suitable source of single photons has been a challenge.

Professor Ronen Rapaport and Dr. Hamza Abudayyeh of the Racah Institute of Physics at the Hebrew University and Professor Monika Fleischer, Annika Mildner and others at the University of Tübingen in Germany have achieved a significant breakthrough which brings us closer to a simple, efficient method of quantum encryption.

 Professor Ronen Rapaport's lab (credit: YITZ WOOLF) Professor Ronen Rapaport's lab (credit: YITZ WOOLF)

While banks and governments are already investing in quantum encryption that relies on laser beams, laser beams often release several photons at once or none at all. In order to achieve optimum security, a source that can emit a fast but steady stream of singly photons, in one direction and at room temperature, is required.

The research team developed a system that uses fluorescent crystals in the form of specks, known as quantum dots, small enough that special microscopes are needed to see them. Each dot is less than a thousandth of the width of a human hair. A laser beam shone at the dot causes it to light up and emit a stream of single photons.

The dots are mounted individually on golden pinheads which are a hundred-thousandth the size of a regular pinhead. These pinheads, called nanocones, can increase the quantum dot emission of photons by 20-fold. The stream of photons is then shot off in a single direction by a Bragg grating, a transparent device that can be used to regulate the wavelength of lasers.

The device can be used not just for quantum encryption, but also in other situations that rely on quantum bits to encode information, such as quantum computation.

"At present, we have a good prototype that has the potential for commercialization in the near future," said Rapaport.

"Laws of science cannot be broken—a single photon cannot be split, no matter how hard one tries.  Mathematical complexities might be very difficult to solve, however they are vulnerable to attack and breaches unlike quantum-based security systems," said Abudayyeh.

The team is working to improve the device so it can provide an even more reliable and efficient stream of single photons for a wide range of quantum technologies.