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Quantum Cloning Machine Could Prevent Hacking

Photonics Spectra
May 2017
OTTAWA, Ontario — Universal optimal quantum cloning of high-dimensional photonic states has been achieved using the symmetrization method. The work has led to the discovery of information that could help system administrators protect quantum computing networks from external attacks.

Researchers at the University of Ottawa demonstrated the feasibility of high-dimensional optimal cloning of orbital angular momentum (OAM) states of single photons and used their discovery to perform a cloning attack to a secure quantum channel. The team cloned the qubits of a secure quantum message as well as the no-cloning theorem allowed — meaning that the team’s clones were almost exact replicas of the original information. The no-cloning theorem, a fundamental law of quantum physics, prohibits perfect copies and is the backbone of security for quantum communications.

The team showed the universality of their technique by cloning several arbitrary input states and characterized the cloning machine by performing quantum state tomography on cloned photons. They experimentally demonstrated a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol to show the robustness of high-dimensional states in quantum cryptography.

But in addition to undermining what was previously thought to be a perfect way of securely transmitting information, the researchers’ analyses revealed promising clues about how to protect against such hacking.

Ebrahim Karimi and Frederic Bouchard of University of Ottawa

Professor Ebrahim Karimi, a member of the University of Ottawa's Department of Physics and holder of the Canada Research Chair in Structured Light, and doctoral student Frédéric Bouchard observe the setup they used to clone the photons that transmit information, called qudits. Courtesy of University of Ottawa.

"What we found was that when larger amounts of quantum information are encoded on a single photon, the copies will get worse and hacking even simpler to detect," said researcher Frédéric Bouchard. "We were also able to show that cloning attacks introduce specific, observable noises in a secure quantum communication channel. Ensuring photons contain the largest amount of information possible and monitoring these noises in a secure channel should help strengthen quantum computing networks against potential hacking threats."

"Our team has built the first high-dimensional quantum cloning machine capable of performing quantum hacking to intercept a secure quantum message," said professor Ebrahim Karimi. "Once we were able to analyze the results, we discovered some very important clues to help protect quantum computing networks against potential hacking threats."

The team hopes that their quantum hacking efforts could be used to study quantum communication systems and how quantum information travels across quantum computer networks.

The open access article was published in Science Advances (doi: 10.1126/sciadv.1601915).  

GLOSSARY
quantum
Smallest amount into which the energy of a wave can be divided. The quantum is proportional to the frequency of the wave. See photon.
Research & TechnologyAmericasopticsdefensequantumquantum cloningorbital angular momentumoptical angular momentumTech Pulse

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