Skip to main content

What Are Quantum Communications?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

Quantum communications are the future of current technological seedlings, but getting effective results has been challenging. This shouldn’t be a surprise, for quantum mechanics has never been described as a simple enterprise. Yet headway is being made in the field, often with surprising results.

Let’s take a look at a few of these and contemplate this new quantum future that is slowly working its way into our lives.

Massive Entanglement

One common quantum mechanical feature that seems to defy physics is entanglement, the “spooky action at a distance” that seems to instantly change the state of a particle based on changes to another one over large distances. This entanglement is easy to produce atomically because we can generate particles with some features dependent on one another, hence the entanglement, but to do so with larger and larger objects is a challenge tied to the unification of quantum mechanics and relativity.

Some headway was made when scientists from Oxford’s Clarendon Laboratory were able to entangle diamonds with a square base of 3 mm by 3 mm and a height of 1 mm. When laser pulses of 100 femtoseconds were fired at one diamond, the other responded even though being separated by 6 inches. This worked because diamonds are crystal in structure and so display great phonon transmission (which is a quasiparticle that is representational of a displaced wave) that became the entangled information transmitted from one diamond to the other (Shurkin).

Working Better

Many people may wonder why we would want to develop quantum transmissions in the first place, for their use in quantum computers seems limited to very precise, difficult circumstances. If a quantum communication system could achieve better results than a classical one, that would be a huge plus in its favor.

Jordanis Kerenidis (Paris Diderot University) and Niraj Kumar first developed a theoretical scenario that allowed for quantum information to be transmitted at a better efficiency than a classical setup. Known as the sampling matching problem, it involves a user asking if a subset pair of data is the same or different.

Traditionally, this would require us to narrow down our groupings via a square root proportion but with quantum mechanics, we can use an encoded photon that is split via a beam splitter and one state sent to the receiver and the other to the holder of the data. The phase of the photon will carry our information. Once those recombine, it interacts with us to reveal the state of the system. This means we only need 1 bit of information to solve the problem quantumly as opposed to potentially way more in the classical approach (Hartnett).

Extending the Range

One of the issues with quantum communications is distance. Entangling information over short distances is easy but to do it over miles is challenging. Maybe instead we could do a hop-scotch method, with steps of entanglement that get transmitted. Work from the University of Geneva (UNIGE) has shown such a process is possible with special crystals that “can emit quantum light as well as store it for arbitrary long times.” It is capable of storing and sending entangled photons with great precision, allowing for our first steps towards a quantum network! (Laplane)

Hybrid Quantum Network

As the above hinted at, having these crystals allows for a temporary storage of our quantum data. Ideally, we would want to have our nodes be similar to ensure that we are accurately transmitting our entangled photons, but limiting ourselves to just a single type also limits its applications.

That is why a “hybrid” system would allow for more functionality. Researchers from ICFO were able to accomplish this with materials that respond differently depending on the wavelength present. One node was “a laser-cooled cloud of Rubidium atoms” while the other was “a crystal doped with Praseodymium ions.” The first node generated a photon of 780 nanometers was able to be converted to 606 nanometers and 1552 nanometers, with a storage time of 2.5 microseconds accomplished (Hirschmann).

This is merely the start of these new technologies. Pop by again every once and a while to see the latest changes we have found in the ever-intriguing branch of quantum communications.

Works Cited

Hartnett, Kevin. “Milestone Experiment Proves Quantum Communication Really is Faster.” Quanta, 19 Dec. 2018. Web. 07 May 2019.

Hirschmann, Alina. “Quantum internet goes hybrid.” innovations report, 27 Nov. 2017. Web. 09 May 2019.

Laplane, Cyril. “A network of crystals for long-distance quantum communications.” innovations report, 30 May 2017. Web. 08 May 2019.

Shurkin, Joel. “In the Quantum World, Diamonds Can Communicate With Each Other.” American Institute of Physics, 01 Dec. 2011. Web. 07 May 2019.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Leonard Kelley