December 20, 2016

Recap | Quantum Puzzles, Quantum Randomness and Quantum Teleportation

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Quantum teleportation may sound like a futuristic means of travel, but it occurs at the particle level. It can enable encryption that is essentially unbreakable.

As part of the physics department’s Fall 2016 Bethe Lecture, Prof. Anton Zeilinger, physics, University of Vienna, discussed concepts in quantum theory that could revolutionize information technology.

The Bethe Lectures is a lectureship endowed by Cornell University to honor Hans Albrecht Bethe, who led the physics department and was awarded the 1967 Nobel Prize in physics for his contributions to the theory of nuclear reactions.

Quantum physics describes the nature of matter on the atomic and subatomic scale. A key concept is that of superposition. Compared to conventional bits which can either take on 1s or 0s, qubits, their quantum counterparts can be superimposed, i.e.: take on 1s and a 0s.

However, our observations affect superposition in such a way that a particle can be observed to be in a single state, not both. On average, equal observations of each state are made.

“There is no cause to go one way over the other,” Zeilinger said.

This choice, or quantum randomness, affects a particle’s interaction with other particles.

Zeilinger and his colleagues conducted experiments to demonstrate the existence and behavior of quantumly entangled photons.

“Two separate quantum systems are separated, but are still described with a common state,” Zeilinger said.

Once photons are entangled, they have identical features, regardless of the distance separating them. Thus, when the state of one photon is determined, the other instantly obtains that same state, a phenomenon known as quantum teleportation. Using the concept of superposition and entanglement, information can be transferred between two entangled particles without any intermediary process, preventing a leak of information during its travel.

A quantum satellite was launched and is designed to shoot a beam of entangled photons toward two data collection sites. The satellite will test quantum encryption techniques. Current encryption involves a key to decode data after transmission. Since quantum teleportation is instantaneous, a more complex key can be involved. With enough entangled photons on the transmitting and receiving end, a key so complex can be applied that the encryption cannot be decoded. If the photon beam through which the key is delivered is intercepted, such an observation would affect the state of the two entangled photons, so that a breach would be immediately detected.