Experiment Demonstrates Possibility of Quantum Internet
A new breakthrough demonstrates how quantum computers could network with each other in the same way that traditional computers connect across the Internet. Quantum computers are machines that exploit different physical properties of atoms than modern PCs for much faster computing speeds.
For the most part, connectivity has taken a back seat in quantum computing research to experiments that focus on creating reliable components for quantum processors or memory. Considering the connectivity is the main driver of traditional computing technology, this omission highlights how far quantum computers have to go before they can be as robust functionality of regular desktops.
Using diamond impurities linked to photons, a team of physicists and computer scientists has engineered a breakthrough that might rectify that imbalance.
Writing in the August 5 issue of the journal Nature, the scientists described how linking a piece of solid-state quantum memory to an easily transmittable particle like a photon created the foundations of what one day might become a quantum computing Internet .
“It’s a building block, a first step towards connecting distant quantum registers,” said Mikhail Lukin, a professor of physics at Harvard University and coauthor of the Nature paper. “It’s a quantum analog of the Internet.”
Quantum computers use the weird tricks of quantum mechanics to solve certain computing problems faster than a traditional computer is physical capable of operating.
To do those fast calculations, quantum computers use a characteristic of particles called spin. Like positive and negative electric charge, the particle characteristic that regular computers use to store information as bits, quantum computers use spin to store multiple kinds of information as qubits. Qubits are linked together using a physics trick called entanglement.
In this case, the qubits are stored in loose electron inside the impurity of a diamond. Then, in the breakthrough described in the Nature paper, the scientists entangled a photon, the particle that makes up visible light, to that qubit by bombarding the diamond with microwave radiation.
Entanglement is the phenomenon wherein two particles change their spin relative to each other instantaneously, regardless of the distance between the two particles.
Once entangled, that photon can potentially transmit the information stored in the qubit through a fiber optic cable, and communicate with a similar photon/diamond array on the other side, thus creating a quantum computing network.
“The entanglement acts as a quantum wire,” said Liang Jiang, a theoretical physics researcher at the California Institute of Technology, and another coauthor of the Nature paper.
Importantly, the qubit in this experiment was held in a solid-state medium. Usually, qubits are stored in gaseous ions isolated in vacuum chambers. While much more stable, gas qubit technology offers no easy solutions for scaling up to the size of a useful computer. By contrast, solid state qubits, such as the diamond, can easily fit together to form larger, working machines.
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