Putting the super into supercomputing
Superconducting computing promises to redefine computational power, both in the classical sense and in terms of quantum computing. However, to take on these new superpowers, the computers require fast, scalable superconducting memories. Enter the EU-funded TERASEC project. “Our goal was to help put the super into supercomputing,” says Francesco Giazotto, the project’s principal investigator. “More specifically, our aim was to demonstrate the practical possibility of the phase coherent manipulation of energy transport.”
The superconducting phase-slip memory cell
At the heart of the project is a superconducting phase-slip memory (PSM) cell. According to Delft University of Technology, phase-slip is the dual process where the difference between two superconducting regions changes by 2π in a short time. “Our PSM is able to efficiently codify the logic state in the direction of the circulating persistent current, as has been commonly defined in flux-based superconducting memories,” explains Giazotto. “But, unlike the latter, our memory scheme does not require large inductance power.” Inductance refers to the property of an electric conductor that causes an electromotive force to be generated by a change in the current flowing. The TERASEC solution also features strong activation energy for phase-slip nucleation, enabling robust topological protection against stochastic phase-slips and magnetic-flux noise. This, along with the solution’s efficient read-out scheme, makes operating the PSM extremely reliable. “These properties make our PSM a promising solution for advanced superconducting classical architectures and flux qubits.”
From flux qubits to Josephson junctions
As Giazotto explains, flux qubits play an important role in superconducting quantum computing. “They are the small, micrometre-sized loops of superconducting metal that are interrupted at several Josephson junctions,” he says. Speaking of Josephson, the TERASEC project, which received support from the European Research Council, touched on that too. The Josephson effect is what happens when a barrier is put between two superconductors placed in proximity to each other. The Josephson junction is the name given to the quantum mechanical device made of two superconducting electrodes that is separated by the barrier. “Our research paves the way for the creation of an entire family of Josephson junction-based components for advanced logical circuits,” notes Giazotto.
Opening the door to new-concept quantum devices
The TERASEC project achieved exactly what it set out to do – it demonstrated the practical possibility of phase coherent manipulation of energy transport in quantum devices. But what does this mean in a practical sense? “Our work opens the door to constructing structures where coherent control of heat transport enables the development of the thermal counterpart of electric devices,” adds Giazotto. “Examples of such devices include transistors, heat memories, and thermal logic gates – all of which could significantly advance, for example, secure technologies for detecting threats such as explosives, weapons and drugs.” Giazotto says that the project’s research also makes the creation of new-concept quantum devices, such as thermal amplifiers, non-volatile memory units, and thermoelectric motors, a real possibility. “Thanks to our research, we can now investigate chargeless modes in solid-state systems, something that was impossible using conventional electronics,” he concludes. Project researchers are now working to validate the PSM cell in relevant environments, including within a quantum computer set-up.
Keywords
TERASEC, supercomputing, energy transport, quantum devices, superconducting computing, quantum computing, phase-slip memory cell, flux qubits, Josephson junctions
