An exotic form of electronic memory made using superconductors could someday be used to make computers that work at unprecedented speeds, say researchers.
The memory cell stores binary data using the direction of an electrically generated magnetic field, representing either a 鈥�1鈥� or 鈥�0鈥�. But superconducting materials experience no electrical resistance, meaning the cell can work with extraordinary efficiency, unlike conventional electronic circuits.
The cell was developed by a team from the University of Technology Ilmenau in Germany and the University of Twente in Holland. Superconducting materials are already used to generate powerful electromagnetic fields in medical equipment and particle accelerators.
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杏吧原创s have also previously used superconducting materials to make simple transistors 鈥� the fundamental components that the control the flow of current through electronic circuits 鈥� but the new cell is the first memory device.
Quantum effects
It uses two superconducting materials that have different quantum properties. These materials are connected to form two segments of a loop, which produces a magnetic flux running in one direction through its centre. Applying second magnetic field to one of the materials then reverses this flux, instantly flipping the memory to its opposite state.
鈥淭he magnetic flux line runs through the circuit like the finger in a wedding ring,鈥� explains David Cardwell, a superconductor engineer at Cambridge University, UK, who was not a member of the team. 鈥淵ou鈥檙e changing the direction of the finger in the wedding ring, and the way it鈥檚 pointing can be used to represent the two states in your digital memory cell.鈥�
The secret to making the superconducting memory cell was to use superconductors that affect electrons differently.
Superconducting materials allow electrons to team up into so-called Cooper pairs, which are linked by vibrations within the material. These electron pairs can then travel through the material without resistance because their quantum state is 鈥渄elocalised鈥�, meaning they can exist simultaneously throughout the entire superconductor.
In the loop
The superconductors used to make the memory cell encourage electrons to move in different directions. Simply connecting them together pushes electrons around the loop to generate the magnetic flux through its centre.
Applying the second magnetic field switches the direction of the electrons, and reverses the direction of the magnetic flux. This change can also be detected in order to 鈥渞ead鈥� from the memory cell.
鈥淒evices using superconductors could be smaller than conventional electronics, and have no speed limits,鈥� Cardwell says. 鈥淏ut they would have the disadvantage of being very sensitive to magnetic fields.鈥�
The magnetic flux line that passes through the memory cell is one millionth of the strength of the Earth鈥檚 magnetic field, Cardwell explains. This means it must be carefully shielded from the outside world in order to function properly.
