'Remarkably close to the minimum permitted by physics': this superconducting memory bit runs at an estimated 5x the limit, but at -269°C the fridge shrinks its claimed million-fold edge over today’s chips considerably

Hebrew University physicists estimate a single superconducting vortex can act as a memory bit at about five times Landauer's limit, at 4.2 kelvin The fivefold figure is a simulation-based estimate anchored to continuous-drive measurements, not a measured erasure, however The release's million-fold edge over conventional computers disregards refrigeration costs Every time a computer erases a bit, it pays an energy toll that physics will not waive; IBM physicist Rolf Landauer pinned down the minimum in 1961: kT ln 2, a figure that scales with temperature and works out to about 2.9 zeptojoules at room temperature.

No real chip comes close, making that gap a favorite target as computing's electricity bill keeps climbing.

Physicists at the Hebrew University of Jerusalem now say they have come within about five times of that floor using a single superconducting vortex, a nanoscale whirlpool of electrical current.

Storing a bit in a whirlpool might be a slightly controversial play The work, published in Nature Communications on September 24 and publicized in a university release on October 11, is a clever measurement, but it has limitations: the device works only at liquid-helium temperatures, and one of the paper's three peer reviewers has opposed the final version.

In a thin superconducting film, a magnetic field can punch through in tiny tubes, each ringed by circulating current and carrying one quantum of flux, and these vortices snag on defects.

The team, led by Yonathan Anahory, used a 55-nanometer niobium film patterned into a strip 10 micrometers wide and cooled to 4.2 kelvin.

Sweeping a steady current through the strip nudged individual vortices into spots where the film's natural disorder offers two neighboring resting places only a few nanometers apart.

The positioning matters here, acting effectively as a store of value: left or right becomes zero or one.

They then rocked each vortex with an alternating current and tracked it with a SQUID-on-tip microscope, a magnetic sensor built onto a tapered glass probe.

The part of the motion that lags behind the push reveals how much energy is lost each cycle.

Anahory said the result puts the bit at roughly five times Landauer's limit, “bringing it remarkably close to the minimum permitted by physics.” The release covers the energy as measured for the actual test, not the cooling aspect, which could significantly reduce the efficiency story here.

The paper adds another caveat here: Its abstract concedes that “our experimental method requires a steady sinusoidal drive incompatible with Landauer’s erasure protocol” and attributes the near-limit figure to numerical analysis.