“In a classical computer, if you need to store information to process later — you can take the data from your CPU and copy it in your RAM or hard drive and fish it back up later,” Morello told Seeker. “You can’t do this in quantum mechanics.”
That’s because of the “no-cloning theorem,” which states that you can never make a copy of quantum information. Instead, you must transfer it from one particle to another, essentially erasing the original. Morello’s demonstration proved that it can be done. This first round of experiments only had an 81 percent success rate, but the team is continuing to refine the process.
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Why is memory an important component of the coming quantum computing revolution? Technically, memory isn’t required to run quantum algorithms in a closed system, and the first large-scale quantum computers may not include any memory capabilities.
But things get trickier if you want to create a quantum network of multiple machines in different locations. You could link quantum computers through the conventional internet, but then you would lose the quantum advantage, namely the incredible speed and virtually unhackable security afforded by the quantum phenomenon of entanglement.
“Having quantum computers connected quantum mechanically is one of the holy grails of our field,” said Morello. To create such a quantum network, information would be sent from machine to machine via photons traveling at the speed of light. When a photon arrives, the computer would need to store the new data temporarily before the qubits process it. That’s where quantum memory comes in.
The next step for Morello and his team is to demonstrate the full chain of quantum networking and storage — photon to electron to nucleus and back again. The recent paper was just a “first embryonic demonstration of nuclear quantum memory,” said Morello, not that it was a piece of cake. His team at UNSW is the only group of quantum physicists in the world that has successfully built silicon quantum devices out of notoriously sensitive subatomic particles.
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How far away are we from the first truly large-scale quantum computer? The largest current machine has 10 qubits. The goal is to build a system running on a million qubits. Scalability is paramount, and that’s where Morello believes his method has the greatest advantage. His single-atom system runs on silicon, the same semiconducting material used by the trillion-dollar microchip industry, which can already squeeze a billion transistors onto a $50 chip.
“Our goal over the next five years is to demonstrate a 10-qubit quantum computer that has all the functionality you need for a universal quantum computer,” Morello said. “The idea is that if we manage to demonstrate all the basic functionalities of quantum bits in silicon at atomic scale, then it should be possible to use the highly controlled, highly reproducible, and highly manufacturable technologies of the silicon microchip industry to scale that up to millions of qubits.”
The potential impact of such a large-scale computer is impossible to predict, not only because we’ve never had a chance to test it, but because we still need to develop the quantum algorithms and quantum software to run these exponentially more powerful machines. One of Morello’s initiatives at UNSW is to develop a quantum engineering curriculum to train future quantum programmers.
“Quantum computing is a truly transformational technology,” Morello said. “It’s not just a faster car or a better airplane. It’s a different object that’s never existed before, and we’re only starting to grasp the power and the capabilities of it.”
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