Stable quantum computing closer to reality with new material
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Researchers at the University of Pennsylvania have discovered a new insulating material which could enable fault-tolerant quantum computing by stabilising quantum states.
Quantum computing harnesses the power of superposition, a common sense-defying subatomic phenomena, to perform calculations far faster than current computers.
In theory, in a quantum computer, qubits (quantum bits) can exist in both states (0 and 1) at the same moment. Information is encoded using these quantum states, although these quantum states are highly unstable and prone to collapsing with the slightest nudge.
Adding an insulator could protect these states long enough for quantum operations to be completed. This could allow for much faster and stronger encryption and decryption, and the modelling of complex scientific systems – which are currently impossible to process, in just minutes.
The research began at the University of Pennsylvania when, during his PhD, Dr Jerome Mlack was working with topological insulators (insulators which carry current only along their surfaces) and a device blew up.
“It kind of melted a little bit,” said Dr Mlack. “What we found is that, if we measured the resistance of this melted region of one of these devices, it became superconducting. Then, when we went back and looked at what happened to the material and tried to find out what elements were in there, we only saw bismuth selenide and palladium.”
Superconducting materials – which can carry current with no resistance at low temperatures – have been predicted to be useful components of fault-tolerant quantum computers when used with topological insulators. Despite this promise, it has proved extremely difficult to achieve electrical contact between insulator and superconductor, with a crack between the materials often reducing electrical contact.
Dr Mlack’s accidentally melted device, however, achieved contact between the insulator and superconductor. Using a furnace, he was able to recreate this material with no contact problems.
“The metal directly enters the nanostructure, providing good electrical contact and can be easily patterned into the nanostructure using standard lithography, allowing for easy scalability of custom superconducting circuits in a topological insulator.”
The device is potentially scalable, meaning that it could be made to fit onto a small chip capable of fitting inside a desktop computer.
“It really is a new potential way of fabricating these devices that no one has done before,” said Dr Mlack. “In general, when people make some of these materials by combining this topological material and superconductivity, it is a bulk crystal, so you don’t really control where everything is.
“Here we can actually customise the pattern that we’re making into the material itself. That’s the most exciting part, especially when we start talking about adding in different types of metals that give it different characteristics.”