LAKE WALES Fla.—Russian scientists claim to have invented a new superconducting memory architecture that will be 100s of times faster and consume dozens of times less power than conventional memory chips. The Moscow Institute of Physics and Technology (MIPT, Russia) working with the Moscow State University (MSU, Russia) claim the architecture can also be used to perform single-flux quantum logic operations for superconducting processors, but admits that commercialization is decades away.
"What we have so far is an idea, a concept," Alexander Golubov, the head of Moscow Institute of Physics and Technology’s Laboratory of Quantum Topological Phenomena in Superconducting Systems told EE Times. "We expect its proof of principle experiment to be commenced in the near future."
After proof of principle, the researchers will begin a "construction testing stage, where the selection of materials and optimization of the topology will be made," said Golubov. "It's hard to evaluate even the approximate time of the technology's possible commercialization, but it's probably decades away."
Diagram of the junction. S – superconductor, I – insulating tunnel barrier, F – ferromagnet, N – normal metal, shaded area – potential barrier arising in the superconducting zone. (Source: Moscow Institute of Physics and Technology)
Nevertheless, at least one analyst is gung-ho on the project, which harnesses a superconducting quantum phenomenon that could be compatible with attempts to build superconducting computers at the U.S. Intelligence Advanced Research Projects Activity (IARPA) and the attempts to build working quantum computers at the National Institute of Standards and Technology (NIST) as well as at companies like D-Wave Systems Inc. (Burnaby, Canada).
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"This research as published shows great promise in the untapped potential of materials science to advance storage and computing designs," Rick Doherty, research director at Envisioneering (Seaford, N.Y.) told EE Times in an exclusive interview. "Superconducting quantum computer research and designs may get a boost in support and funding thanks to this team’s remarkable materials engineering work."
The unique part of the MIPT/MSU project is a new type of superconducting junction and memory architecture. Normal Josephson junctions use sandwiches of superconductor-insulator-superconductor such as in D-Wave's quantum computer, but MIPT/MSU's memory uses adds a normal-metal/ferromagnetic-metal (N/F) interlayer adjacent the insulator to achieve two stable conduction currents that can quickly switch between 1s and 0s. Since superconductors conduct current with zero resistance, the two stable states should take no energy to maintain, argue the scientists in their paper Superconducting phase domains for memory applications.
The MIPT/MSU researchers claim that read and write operations will be hundreds or even thousands of times faster than with conventional ferromagnetic memory technologies--depending on the final materials formulation--taking just a few hundred picoseconds to switch a 0 to a 1 or visa versa.
Josephson junctions have been used for years in sensors (superconducting quantum interference devices--Squids) and in quantum computer prototypes at NIST and in production models at D-Wave. However, even the most futuristic ferromagnet memory elements use the magnetic moment (spin direction) to switch from 0 to 1 and visa versa. This takes extra pulses of current to switch the spin, slowing down writing to the device, as well a not being able to pack them as densely as Josephson junctions can be packed, according to MIPT/MSU.
The MIPT/MSU team, rather, encodes 0s and 1s on two different stable "minimum energy" states into which their special Josephson junctions can relax. As far as they know, the MIPT/MSU team is the first to observe these two stable minima involving the longitudinal (vertical) and transverse (horizontal) dimensions of the layers of their specially prepared junction.
Superconducting currents when reading various states of the memory cell, where the greater the current, the larger the arrow.
(Source: Moscow Institute of Physics and Technology)
The scientists intent to switch between the longitudinal and transverse states using an injection current through one of the layers of the superconductor sandwich. Reading will be done with a small current that flows through the whole junction. Both writing and reading should be 100s or even 1000s of times faster than conventional spin-switching and reading, according to MIPT/MSU.
In addition, the single-layer ferromagnetic memory system can also perform single-flux quantum logic, allowing the same material to be used for processor circuits, enabling the clock speed of such processor and memory circuits to be boosted to 100s of GHz while consuming dozens of times less power, the MIPT/MSU group claimed.
How it works
Normal Josephson junctions invented in the 1960s by British physicist Brian Josephson use a superconductor-insulator-superconductor architecture which are switched by Cooper-pairs of electrons tunneling through the sandwich. For instance, the Squid uses the phenomena to make a sensor that is exceptionally sensitive to magnetic fields. D-Wave uses them to find the minima of complex linear equations using a quantum annealing algorithm. And the IARPA superconducting computer project is trying to build processors using the same architecture and algorithm. Now the MIPT/MSU group has extended the architecture, using an additional ferromagnetic layer, to invent a new superconducting memory architecture that can also perform single-flux quantum logic operations.
Funding was provided by the Russian Science Foundation of the Government of the Russian Federation.
— R. Colin Johnson, Advanced Technology Editor, EE Times