Superconducting Whirlpool Stores a Bit at Five Times the Physical Energy Floor
Hebrew University researchers measured a single magnetic vortex flipping between two positions and found it needs only about 5 times Landauer's limit, a million times less than a modern computer.
Every time a computer stores or erases information it spends energy. The amount is tiny for one operation, but billions of operations happen every second, and for decades scientists have asked how little energy a memory device could use before hitting the limit set by the laws of physics. Researchers at the Hebrew University of Jerusalem now report that they have come close.
Their study, published in Nature Communications, demonstrates a superconducting memory bit that operates at about five times Landauer's limit, the theoretical minimum energy needed to erase one bit of information. Instead of conventional electronic components, the team stored the bit in a superconducting vortex, a tiny magnetic whirlpool that forms inside certain materials when they are cooled to extremely low temperatures. They trapped a single vortex between two stable positions, and, like the zeros and ones in every digital computer, those two positions represented one bit.
"Our work measures the energy required to operate a superconducting vortex-based memory bit," said Dr. Yonathan Anahory, who led the study with Nofar Fridman. "We found that it can run at approximately five times Landauer's limit, bringing it remarkably close to the minimum permitted by physics." For perspective, a modern computer typically needs more than a million times more energy to perform the same operation.
Measuring such a small amount of energy was the hard part. Rather than trying to detect the minute heat released as the vortex moves, the researchers tracked its magnetic response using an ultrasensitive SQUID-on-tip microscope, a sensor built on the tip of a probe. "A vortex is an exceptionally small and delicate object, so measuring the energy dissipated by its motion is a major experimental challenge," Fridman said. "By following its magnetic response, we were able to compare its energy cost with the fundamental limits of information processing."
The researchers stress that the device is still experimental. It runs only at around 4 kelvin, or minus 269 degrees Celsius (minus 452 degrees Fahrenheit), which makes it unsuitable for everyday computers. But quantum computers already operate at similar cryogenic temperatures, and the team says devices like this could one day offer an energy-efficient way to store classical information inside those machines.
Other physical systems have approached Landauer's limit before, but the researchers say this is the first demonstration of such low energy consumption using a single superconducting vortex. The paper, "Approaching Landauer's limit in a single superconducting vortex memory bit," is a proof of principle, and more work will be needed before the technology can be scaled into practical memory elements for cryogenic and quantum computing.
