Unsolvable problems will be solved by new analogue quantum computers
The most potent digital supercomputers cannot handle difficult physics problems, but physicists have developed a new kind of analogue quantum computer that can.
Researchers from Stanford University in the United States and University College Dublin (UCD) in Ireland have recently demonstrated that a novel kind of highly specialised analogue computer, whose circuits feature quantum components, can solve problems from the cutting edge of quantum physics that were previously out of reach. Their findings were published in the journal Nature Physics. Such gadgets may be able to provide insight into some of the most significant unresolved physics problems when scaled up.
For instance, superconducting materials, such as those used in MRI machines, high-speed trains, and long-distance energy-efficient power networks, currently operate only at extremely low temperatures, limiting their wider use. As a result, scientists and engineers have long sought to better understand superconductivity. Finding materials that are superconducting at room temperature, which would revolutionise their usage in a variety of technologies, is the holy grail of materials science.
The paper’s co-author and director of the UCD Centre for Quantum Engineering, Science, and Technology (C-QuEST), Dr. Andrew Mitchell, is also a theoretical physicist at the UCD School of Physics.
He stated: “Even the most advanced digital classical computers cannot answer some issues because they are simply too complex. This kind of calculation is well above existing capabilities due to the exponential processing time and memory needs needed to replicate the features of realistic models, such as the high-temperature superconductors, which is a particularly important example.”
“However, the digital revolution’s technological and engineering advancements have made it possible to govern matter at the nanoscale in a way that has never before been possible. This has made it possible for us to create specialised analogue computers known as “Quantum Simulators,” which use the innate quantum mechanical features of their tiny components to solve particular quantum physics models. Even while we haven’t yet been able to create a powerful enough general-purpose programmable quantum computer, we can already create custom analogue devices with quantum components that can address particular quantum physics challenges.”
Researchers from Stanford, UCD, and the Department of Energy’s SLAC National Accelerator Laboratory developed the nanoelectronic circuit that serves as the architecture for these new quantum devices (located at Stanford). The gadget was constructed and operated by Stanford’s Experimental Nanoscience Group under the direction of Professor David Goldhaber-Gordon, while Dr. Mitchell of UCD handled the theory and modelling.
We constantly create mathematical models that we hope will capture the essence of the phenomena we are interested in, but even if we believe they are accurate, they frequently cannot be solved in a reasonable amount of time, according to Prof. Goldhaber-Gordon, a researcher with the Stanford Institute for Materials and Energy Sciences.
According to Prof. Goldhaber-Gordon, “we have these knobs to turn that no one has ever had before” with a quantum simulator.
Why analogue simulation of quantum materials?
According to Goldhaber-Gordon, the fundamental concept behind these analogue devices is to create a sort of hardware approximation to the issue at hand rather than creating computer code for a programmable digital computer. Let’s take the scenario if you wanted to forecast the date of eclipses as well as the motions of the planets in the night sky. You may achieve this by building a mechanical model of the solar system, in which the motion of the moon and planets is represented by revolving, interlocking gears, which are turned by a crank.
A shipwreck from more than 2000 years ago off the coast of a Greek island actually included such a system. One could consider this gadget to be a very early analogue computer.
Analog machines were still utilised in the late 20th century to perform mathematical operations that were too complex for even the most sophisticated digital computers at the time.
However, the gadgets must incorporate quantum components in order to address challenges in quantum physics. The features of the electronic circuits with nanoscale components used in the new Quantum Simulator architecture are subject to the principles of quantum physics. Importantly, a large number of these components may be produced, and they all function essentially the same way.
This is essential for analogue simulation of quantum materials because each electronic component in the circuit acts as a stand-in for an atom being simulated. The various electronic parts of the analogue computer must behave exactly the same, much as different atoms of the same sort do in a substance.
As a result, the novel architecture presents a special means to advance technology from isolated units to vast networks that can simulate bulk quantum matter. The researchers also demonstrated how these devices may manufacture novel microscopic quantum interactions. A new generation of scalable solid-state analogue quantum computers is being developed as a result of the work.
The first step toward solving the most difficult problems
The researchers first looked at a straightforward circuit made up of two connected quantum components to show the potential of analogue quantum computation utilising their novel Quantum Simulator platform.
The apparatus reproduces a model of two atoms connected by an odd quantum interaction. The researchers were able to create a novel state of matter known as “Z3 parafermions” in which electrons appear to have only a third of their normal electrical charge. These elusive states, which have not yet been produced in a lab using an electrical device, have been proposed as the foundation for upcoming topological quantum computation.
We want to model much more complex systems that existing computers are unable to handle by scaling up the Quantum Simulator from two to numerous nano-sized components, according to Dr. Mitchell. This might be the first step toward solving some of our quantum universe’s most difficult problems.
This work was published in: Pouse, W., Peeters, L., Hsueh, C.L. et al. Quantum simulation of an exotic quantum critical point in a two-site charge Kondo circuit. Nat. Phys. (2023). https://doi.org/10.1038/s41567-022-01905-4
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