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Physicists have built the world's fastest quantum simulator

Atomic level inquiry

The world’s fastest quantum simulator models an interaction between a many-body system of more than 40 atoms within one billionth of a second, according to research published on Wednesday.

Replicating a many-body system experimentally is a lively area of research, as it gives scientists a way to study quantum mechanical phenomena such as superconductivity, magnetism and quantum computing.

To build a quantum simulator, a system of particles must be mutually interacting to create a strongly correlated system.

By trapping ultracold, slightly radioactive rubidium (87Rb) atoms with a magneto-optical trap (MOT), which slows the atoms down with a laser beam, a team of researchers has created a quantum simulator.

First, the rubidium atoms are chilled to 70 microkelvin – a smidgen above absolute zero – and trapped and excited with a laser till they reach “Rydberg states.” The outer electron moves in an orbital size from sub-micrometre to several tens of micrometres to create a large dipole moment.

These dipole moments allow a strong interaction to develop between a pair of Rydberg atoms, creating a strongly correlated system.

The results, published in Nature Communications [paywalled], show that a pulsing laser beam makes the interaction occur within picoseconds, making it the world’s fastest quantum simulator, the researchers claim.

The motion between the electrons can be controlled by changing the strength of the interactions between the Rydberg atoms, which are controlled with a laser.

One of the main motivations behind building a quantum simulator is that it allows researchers to study the reactions behind quantum mechanics that are too complex for a supercomputer to handle.

Japan is currently building a post-K supercomputer under its Flagship 2020 project in partnership with Fujitsu. Although Post-K will be one of the world’s fastest supercomputers operating at exaflops – or a quintillion (1018) floating point operations per second – it’s not powerful enough to calculate the energy of a strongly correlated system when it contains more than 30 particles.

Quantum simulators have known properties and can be controlled, making them easier to study. Many countries including China, the US, Russia, and the UK have invested in constructing quantum simulators in a bid to be the first to build an advanced quantum computer. ®

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