Physics

Quantum Switches Controlled By Single Photons

May 6, 2014 | by Lisa Winter

Photo credit: NASA/Goddard Space Flight Center

Quantum computing has the potential to revolutionize computing by exponentially increasing speed, computing power, and security as single atoms would be capable of performing tasks. Though quantum computing is probably overkill for the typical person, it holds a great deal of promise for researchers and others who need ramped up computing. A team of researchers led by Mikhail Lukin of Harvard University have demonstrated an ability to use single atoms as gates that can block the flow of electrons and can be operated with one photon. The details of the research have been described in Nature

“Conceptually, the idea is very simple,” Lukin told the Harvard Gazette. “Push the conventional light switch to its ultimate limit. What we’ve done here is to use a single atom as a switch that, depending on its state, can open or close the flow of photons … and it can be turned on and off using a single photon.” When many switches are added together, it could essentially act like a computer.

Lukin is currently eyeing the possibility of putting this technology into fiber-optic cables, which would offer maximum security through encryption. While there are short-range possibilities with this technology, the quantum switches could increase the distance by which information could be securely transmitted from tens of kilometers up to thousands of kilometers.

The researchers developed a system that combined the photon switches with traditional vacuum tubes. “Conventional computers were initially built using vacuum tubes, and people eventually developed integrated circuits used in modern computers,” Lukin went on to say in the Harvard Gazette. “Where quantum systems stand today, the best systems are still analogous to vacuum tubes. They typically use vacuum chambers to isolate and hold single atoms using electromagnetic fields.”

Once the atoms have been captured in the vacuum tubes, lasers act like optical tweezers to hold one and then chill it nearly to absolute zero. The atom is then moved near the chip before it is blasted with microwaves and enters a state of quantum superposition. This state is so delicate that getting hit with even a single photon is capable of changing it. 

These switches probably won’t see action inside a quantum network for about another decade, as there are different approaches that are more advanced, according to Jeff Thompson; a grad student who is co-author of the paper. However, these single-atom switches can interact with light that travels through optical fibers, making this next-generation computing possible.

[The main image is credited to NASA/Goddard Space Flight Center and has been used in accordance with CC BY 2.0]

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