New quantum simulator might probe the exotic effects of quantum criticality between two states

A new simulator may be the breakthrough that allows scientists to probe strange quantum phenomena.

Among the most exciting and intriguing areas of investigation in modern physics are the  exotic effects seen when quantum objects “hover” between two quantum states. Fields which exist in this “quantum critical” regime include high-temperature superconductors and some quantum computing research.

Exciting as quantum criticality is, its complexity is a major drawback. The mathematics is often too difficult to solve and conventional modern computers not powerful enough to simulate the systems, particularly those with more than just a couple of atoms.

Researchers at Stanford University and the US Department of Energy are attempting to build a quantum simulator to probe quantum criticality.

“We’re always making mathematical models that we hope will capture the essence of phenomena we’re interested in, but even if we believe they’re correct, they’re often not solvable in a reasonable amount of time,” says Stanford physics professor David Goldhaber-Gordon.

Goldhaber-Gordon likens a quantum simulator to a mechanical solar system model. The model-maker turns a crank which, through a series of interlocked gears, gives a representation of the motion of the planets and moons and can be used as a predictive tool.

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Only, Goldhaber-Gordon’s team is seeking to simulate the highly probabilistic and exotic effects of quantum critical points.

They begin by thinking of these systems as a lattice of atoms in a sea of electrons.

To be useful, a quantum simulator needs to have stand-ins for the atoms that are near-identical and interact with each other as well as the electron reservoir. The simulator also needs to be tunable so that its parameters can be altered to gain insight into the physical effects.

This is easier said than done with most quantum simulators.

The researchers hit the jackpot based on the work of French physicist Frédéric Pierre. They developed a quantum simulator built on so-called “metal islands” sitting in specially-designed pools of electrons known as two-dimensional electron gas.

“They’re very difficult to make,” according to  graduate student Winston Pouse. But make them they did. The team was successful in creating a two-atom quantum criticality simulator.

“While we have not yet built an all-purpose programmable quantum computer with sufficient power to solve all of the open problems in physics, we can now build bespoke analogue devices with quantum components that can solve specific quantum physics problems,” says team member Dr Andrew Mitchell from University College Dublin.

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The team hopes to build more efficient devices by reducing the size of the metal islands. They also believe their work can be readily scaled up to simulate larger systems.

The research is published in Nature Physics.

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