Giant atoms ‘trapped’ for record time at room temperature

Giant atoms just got a boost as contenders for making the best quantum simulators and computers, as researchers controlled them for an unprecedentedly long time for a room-temperature experiment.

Grab an atom, tune its quantum properties with electromagnetic pulses or laser light – changing the energies of its electrons – and you can use it to encode information. Do this with thousands of atoms and you have a quantum computer or a simulator for exotic quantum materials. However, after a while, atoms can spontaneously change their state, which introduces errors. They are only controllable, and therefore useful, during a finite “lifetime”, which was previously a maximum of 1400 seconds for room-temperature experiments. Scientists have been able to trap atoms for longer, but those approaches required the whole setup be placed in a giant fridge, posing logistical challenges.

Zhenpu Zhang and Cindy Regal at the University of Colorado Boulder and their colleagues have now shattered that room-temperature record. They used Rydberg atoms, which are super-sized in diameter because some of their electrons are far from their nuclei. The team loaded the atoms into a container that had been emptied of all air particles which could disturb them, then grabbed each atom with lasers or “optical tweezers”. This is a standard way of controlling Rydberg atoms, which are extremely sensitive to electromagnetic fields and light.

The researchers also added a layer of copper to the container’s sides, then cooled the coating to -269°C (-452°F). This protected the atoms from heat, which can change their states. Additionally, Zhang says any stray air particles got stuck to the copper siding, similar to how warm water droplets condense on a cold surface, thus improving the vacuum inside the container. Consequently, the team could keep the atoms trapped and well-controlled for about 50 minutes – 3000 seconds, or roughly twice as long as similar past experiments.

Zhang started building this setup about five years ago from near-scratch, says Regal. “This is like a total revamp of how you think about making these experiments,” she says.

Clément Sayrin at the Kastler Brossel Laboratory in France says the new approach could make it possible to manipulate more atoms, which would increase the computational power of any computer or simulator made from them. “Three thousand seconds is very long. You have to work hard to have these long lifetimes for these atoms,” he says. However, having more atoms in the chamber would also mean having to use more lasers to control them, which could decrease the atoms’ lifetimes, so more engineering challenges remain, says Sayrin.