Researchers have hit a new speed limit on the movement of quantum information

With the advances made in quantum physics in recent years, more and more people are becoming interested in quantum computers, especially the quantum internet. The latter is considered to be more secure compared to the Internet protocol currently in use and is based on qubit exchange.

In contrast to a classic bit, which works like a switch, ie has to be on (1) or off (0), the qubits overlap. They can therefore be 0 and 1 at the same time. But how fast can atoms move in the quantum world? To answer this question, an international group of scientists led by Dr. Andrea Alberti from the University of Bonn carried out an unprecedented experiment.

Cooled cesium atoms

To make it easier for us to understand the basics of her studies, Alberti took the example of a waiter who has to serve a tray filled with champagne a few minutes before midnight on New Year’s Eve. This serves each guest by moving quickly. Thanks to his technique, which has been perfected over time, he still manages not to spill a drop of the precious liquid.

To make this possible, the server tilts the tray slightly to prevent the drink from overflowing. Halfway across the table, he tilts it in the opposite direction and slows down. Only when he comes to a standstill does he straighten it. The researchers only used cooled cesium atoms as part of their experiment, but not champagne.

Move atoms around in no time

The bowl has been replaced by an optical trap consisting of two laser beams. As Science Alert explains, this trap, known as an optical grid, appears when two laser beams meet. This creates interference from superimposed beams. The stratification creates a stationary wave of light in the form of mountains and valleys.

Close up on a quantum computer. Photo credit: Shutterstock / Bartlomiej K. Wroblewski

Atoms were placed in these valleys and the two-dimensional lattice set in motion to determine the maximum speed with which charges could be moved. “Our goal was to get the atom to its destination as quickly as possible without it coming out of the valley, so to speak,” says Alberti in the research results published in the journal Physical Review X.

A distance of 0.5 micrometers

The Soviet physicists Leonid Mandelstam and Igor Tamm had theoretically proven the existence of a speed limit in the quantum universe more than 60 years ago. In particular, the duo showed that the maximum speed of a quantum process depends on the uncertainty of the energy, more precisely on the degree of freedom of the controlled particle in relation to its possible energy states.

During their experiment, Andrea Alberti and his colleagues discovered that the diffusion of the energies of quantum states in this valley is greater the deeper the valley in which the cesium atom is enclosed.

Finally, the particle could be moved quickly. If the researchers behind this study are to be believed, the speed limit in the quantum domain is 17 millimeters per second to move at least one atom without losing its original state. To get this result, they moved cesium atoms a distance of 0.5 micrometers.

Back to top button