Subatomic quantum memories in semiconductors demonstrated
They were able to use this control to create an “entangled state,” representing a connection between the quantum memories and electrons trapped in the semiconductor material. This, say the researchers, effectively shows how one could encode and write quantum information onto the core of a single atom, unlocking the potential for building qubits that can remain operational – or “coherent” – for extremely long times, which could hold major implications for quantum computing.
“Just like a desktop computer has different types of memory for various purposes, we envision quantum technologies will have similar needs,” says Alexandre Bourassa, a graduate student at the Pritzker School of Molecular Engineering at the University of Chicago and co-first author of a study on the research. “Our trapped electron is like a CPU, where different nuclear spins can effectively be used as a quantum RAM and hard-drive to provide both medium- and long-term storage of quantum information.”
Semiconductor materials are arrangements of atomic nuclei held together by electronic bonds. Some, but not all, of these nuclei possess a property called “spin,” which enables them to behave as tiny quantum magnets. Nuclei that do have spin can be used to encode quantum information, say the researchers.
“The spins of atomic nuclei are one of the most robust quantum systems we know of,” says co-first author Chris Anderson, a UChicago postdoctoral scholar. “Their quantum state can last for hours or even days. This makes them ideal for building quantum memories. In a world where most quantum technologies can only retain their information for a fraction of a second, this is an eternity.”
To interact with these nuclei, the scientists used techniques similar to those used in magnetic resonance imaging (MRI), but replaced the bulky magnetic chamber with just a single electron. Using this “atomic scale MRI,” the scientists were able to address and control the nuclei that form the core of individual atoms.
“The trick is to precisely control the number of nuclei carrying the desired spin,” says graduate student Nikita Onizhuk, a co-author who developed a theoretical model to interpret and guide the experimental breakthroughs. “If there are too few, one will not have enough available memories in the device, but if there are too many, it won’t be possible to isolate and control them independently.”
Working with theory and materials growth collaborators, the researchers showed that it’s possible to optimize these quantum memories.
“We believe that we can develop materials that have tens of high-quality quantum memories within a smaller footprint than a single state-of-the-art transistor you’d find in today’s integrated circuits,” says David Awschalom, the Liew Family Professor in Spintronics and Quantum Information in the Pritzker School of Molecular Engineering.
This work, say the researchers, establishes the key components necessary for creating quantum technologies in semiconductor devices and will be an important platform for a future quantum internet. For more, see “Entanglement and control of single nuclear spins in isotopically engineered silicon carbide.”
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