New analog quantum computers to solve problems that previously had no solution

Physicists have invented a new type of analog quantum computer that can tackle difficult physical problems that the most powerful digital supercomputers can’t solve.

New research published in physics of nature by collaborating scientists from Stanford University in the US and University College Dublin (UCD) in Ireland has shown that a novel type of highly specialized analog computer, whose circuits feature quantum components, can solve problems in quantum physics. cutting edge that were previously beyond reach. When scaled up, these devices can shed light on some of the most important unsolved problems in physics.

For example, scientists and engineers have long wanted to gain a better understanding of superconductivity, because superconducting materials—such as those used in MRI machines, high-speed train and long-distance energy-efficient power grids—currently operate only at extremely low temperatures, limiting their wider use. The holy grail of materials science is finding materials that are superconducting at room temperature, which would revolutionize their use in a host of technologies.

Dr Andrew Mitchell is Director of the UCD Center for Quantum Engineering, Science and Technology (C-QuEST), a theoretical physicist in the UCD School of Physics and co-author of the paper.

He said: “Certain problems are simply too complex for even the fastest digital classical computers to solve. Precise simulation of complex quantum materials such as high temperature superconductors is a really important example: that kind of computing is way beyond current capabilities because of the exponential computing time and memory requirements needed to simulate realistic model properties.”

“However, technological and engineering advances driving the digital revolution have brought with them the unprecedented ability to control matter at the nanoscale. This has allowed us to design specialized analog computers, called ‘Quantum Simulators,’ that solve specific models in physics. by taking advantage of the inherent quantum mechanical properties of its nanoscale components.While we have not yet been able to build an all-purpose programmable quantum computer with enough power to solve all open problems in physics, what we can do now is build analog devices at with quantum components that can solve specific problems in quantum physics.”

The architecture of these new quantum devices involves hybrid metal-semiconductor components embedded in a nanoelectronic circuit, devised by researchers at Stanford, UCD, and the Department of Energy’s SLAC National Accelerator Laboratory (located at Stanford). Stanford’s Experimental Nanoscience Group, led by Professor David Goldhaber-Gordon, built and operated the device, while theory and modeling was done by Dr Mitchell at UCD.

Professor Goldhaber-Gordon, a research fellow at the Stanford Institute of Materials and Energy Sciences, said: “We are always creating mathematical models that we hope capture the essence of the phenomena we are interested in, but even if we believe they are correct, often they don’t. can be resolved in a reasonable amount of time.

With a quantum simulator, “we have these knobs to turn that no one has ever had before,” said Professor Goldhaber-Gordon.

Why analog?

The essential idea of ​​these analog devices, Goldhaber-Gordon said, is to build a kind of hardware analogy for the problem you want to solve, rather than writing computer code for a programmable digital computer. For example, suppose he wants to predict the movements of the planets in the night sky and the timing of eclipses. You could do this by building a mechanical model of the solar system, where someone turns a crank and interlocking spinning gears represent the movement of the moon and planets.

In fact, such a mechanism was discovered in an ancient shipwreck off the coast of a Greek island that dates back more than 2,000 years. This device can be seen as a very early analog computer.

Not to be scorned, analog machines were even used at the end of the 20th century for mathematical calculations that were too difficult for the most advanced digital computers at the time.

but to solve quantum physics problems, the devices must involve quantum components. The new architecture of Quantum Simulator implies electronic circuits with nanoscale components whose properties are governed by the laws of quantum mechanics. It is important to note that many of these components can be manufactured, each of which behaves essentially identically to the others.

This is crucial for the analog simulation of quantum materials, where each of the electronic components in the circuit is a representative of an atom being simulated and behaves like an “artificial atom”. Just as different atoms of the same type in a material behave identically. , so must the different electronic components of the analog computer.

Therefore, the new design offers a unique path to scale the technology from individual units to large networks capable of simulating bulk quantum matter. Furthermore, the researchers demonstrated that new microscopic quantum interactions can be engineered into such devices. The work is a step toward developing a new generation of scalable solid-state analog quantum computers.

quantum scoops

To demonstrate the power of analog quantum computing using their new Quantum Simulator platform, the researchers first studied a simple circuit comprising two coupled quantum components.

The device simulates a model of two atoms joined by a peculiar quantum interaction. By adjusting the electrical voltages, the researchers were able to produce a new state of matter in which electrons appear to have only a fraction of 1/3 of their usual electrical charge, so-called “Z3 parafermions.” These elusive states have been proposed as the basis for future topological quantum computation, but they have never before been created in the laboratory in an electronic device.

“By expanding the Quantum Simulator from two to many nanometer-sized components, we hope to be able to model much more complicated systems that current computers cannot handle,” said Dr. Mitchell. “This could be the first step in finally unraveling some of the most perplexing mysteries of our quantum universe.”