Princeton University Physicists Managed To Pass Information From An Electron To Photon

Quantum computers are the future of computing. Instead of working with one state at a time (0 and 1), they use qubits – the quantum analogue of a bit – that are capable of having two states (o and 1) at the same time. This means that a quantum computer is capable of calculating immensely complex stuff, like worldwide weather models, much faster than standard computers (or supercomputers) with just a couple of hundreds of qubits.

The problem, however, is programming a quantum computer so it can actually solve complex problems. Scientists had no luck in coming up with the solution, but one recent study maybe managed to make the problem a bit easier, since the scientists who conducted the study managed to pass quantum information from a single electron to a photon, the first step in making quantum computers a reality.

The research was published in Science, it was conducted at Princeton University by a group of physicists who made a device allowing for a quantum state to be passed from one particle to another.

Xiao Mi, a graduate student in Princeton’s Department of Physics and one of the physicists involved in the research stated that “We now have the ability to actually transmit the quantum state to a photon,” explaining that  “This has never been done before in a semiconductor device because the quantum state was lost before it could transfer its information.”

Image Credit: Princeton University

The research lasted for five years, with the results published recently. Scientists managed to pass the quantum state information by trapping an electron and a photon inside a device constructed by HRL laboratories (owned by General Motors and Boeing). The device is a classic semi-conductor chip made from silicon and silicon-germanium, two commonly used materials.

The chip is made out of layers of silicon, with a number of nanowires (thinner than a single human hair) placed at the top. Nanowires are used for powering the chip, and the energy from them was used to trap an electron in between two silicon layers, inside quantum dots ( microscopic structures able to trap single electrons).

The problem with quantum information is that it is extremely brittle, even measuring it can corrupt the information (a strange phenomenon found in quantum mechanics) so the main goal was finding out a way of passing quantum state between two particles without messing it up.

Jason Petta, a professor of physics at Princeton tried to explain the process. He said that “In our device, the state of the qubit is encoded in the position of the electron. The electron is trapped in a double well potential where the electron can occupy the left well, the right well, or be in a superposition state: both left and right at the same time. The information is therefore stored in the position of a single electron.”

Image Credit: Princeton University

The physicists used photons as a medium for exchanging quantum information between electrons. They used photons because they are less sensitive to disruption and can travel through optic cables, as well as through photonic circuits that could be used when constructing a quantum supercomputer. For instance, they can carry information between two quantum chips, potentially forming the circuits that could carry quantum info between one electron to another.

Jason Petta said that “Just like in human interactions, to have good communication a number of things need to work out —it helps to speak the same language and so forth,” continuing by saying that “We are able to bring the energy of the electronic state into resonance with the light particle, so that the two can talk to each other.”

Next step is making the device able to influence the spin of electrons, a first step towards enabling actual quantum programming. “Our next step is to couple spin to light,” said Petta. “The spin of the electron, or its magnetic moment, has some advantages, as the spin state of an electron in silicon can remain coherent for a much longer time. So in principle, one can perform many gate operations electrically before the spin superposition state collapses.”

In other words, we may see a working quantum computer in the next decade or so. There are still many obstacles to pass, but this research is an important step in our path to learn secrets of quantum computing.


Source: Princeton University

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