| Researchers have developed a new method of trapping rubidium atoms in a lattice of light, which could help the development of quantum computing. |
By manipulating a laser to place individual rubidium atoms near the surface of a lattice of light, researchers at MIT and Harvard University have developed a new method for connecting particles that could help in the development of powerful quantum computing systems.
As described in a paper published in the journal Nature, the new technique allows researchers to bind a lone atom of the metal rubidium with a single photon.
This pairing allows both the atom and photon to switch the quantum state of the other particle, providing a mechanism through which quantum-level computing operations could take place.
"We have demonstrated basically an atom can switch the phase of a photon. And the photon can switch the phase of an atom." |
“This is a major advance of this system,” says Vladan Vuletić, a professor in MIT’s Department of Physics and Research Laboratory for Electronics (RLE), and a co-author of the paper. “We have demonstrated basically an atom can switch the phase of a photon. And the photon can switch the phase of an atom.”
The photons can have two polarization states, and interaction with the atom can change the photon from one state to another. Also interaction with the photon can change the atom’s phase, which is equivalent to changing the quantum state of the atom from its “ground” state to its “excited” state.
In this way the atom-photon coupling can serve as a quantum switch to transmit information — the equivalent of a transistor in a classical computing system. By placing many atoms within the same field of light, the researchers may be able to build networks that can process quantum information more effectively.
“You can now imagine having several atoms placed there, to make several of these devices — which are only a few hundred nanometers thick, 1,000 times thinner than a human hair — and couple them together to make them exchange information,” Vuletić adds.
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However, researchers are in the early stages of determining which materials best allow for quantum-scale computing. The MIT and Harvard researchers have been examining photons as a candidate material, since photons rarely interact with other particles. For this reason, an optical quantum computing system, using photons, could be harder to knock out of its delicate alignment. But since photons rarely interact with other bits of matter, they are difficult to manipulate in the first place.
In this case, the researchers used a laser to place a rubidium atom very close to the surface of a photonic crystal cavity, a structure of light. The atoms were placed no more than 100 or 200 nanometers — less than a wavelength of light — from the edge of the cavity. At such small distances, there is a strong attractive force between the atom and the surface of the light field, which the researchers used to trap the atom in place.
Other methods of producing a similar outcome have been considered before — such as, in effect, dropping atoms into the light and then finding and trapping them. But the researchers found that they had greater control over the particles this way.
“For me what is still amazing, after working in this for 20 years,” Vuletić says, “is that we can hold onto a single atom, we can see it, we can move it around, we can prepare quantum superpositions of atoms, we can detect them one by one.”
SOURCE MIT
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