Rare form of quantum matter created with molecules for the first time

Scientists have produced a rare form of quantum matter known as a Bose-Einstein condensate (BEC) using molecules instead of atoms.

Made from chilled sodium-cesium molecules, these BECs are as chilly as five nanoKelvin, or about -459.66 °F, and stay stable for a remarkable two seconds.

“These molecular BECs open up an new research arenas, from understanding truly fundamental physics to advancing powerful quantum simulations,” noted Columbia University physicist Sebastian Will. “We’ve reached an exciting milestone, but it’s just the kick-off.”

Understanding Bose-Einstein Condensate (BEC)

A Bose-Einstein Condensate (BEC) represents a state of matter that occurs when a collection of bosons, particles that follow Bose-Einstein statistics, are cooled to temperatures very close to absolute zero.

Under such extreme conditions, a significant fraction of the bosons occupy the lowest quantum state, resulting in macroscopic quantum phenomena.

This means that they behave as a single quantum entity, effectively “collapsing” into a single wave function that can be easily described using the principles of quantum mechanics.

The fascinating aspect of BECs stems from their superfluid properties — exhibiting zero viscosity as they flow, which allows them to move without dissipating energy.

This unique property enables BECs to simulate other quantum systems and explore new realms of physics.

For instance, studying BECs can provide insights into quantum coherence, phase transitions, and many-body interactions in quantum gases.

The creation of molecular BECs, like those involving sodium-cesium molecules, extends this exploration even further, potentially leading to breakthroughs in quantum computing and precision measurements.

Ultracold BEC odyssey

The journey of BECs is a long and winding one, dating back a century to the works of physicists Satyendra Nath Bose and Albert Einstein.

They prophesied that a cluster of particle cooled to the brink of standstill would merge into a singular macro-entity, governed by the dictates of quantum mechanics. The first true atomic BECs emerged in 1995, 70 years after the original theoretical predictions.

Atomic BECs have always been relatively simple – round objects with minimal polarity-based interactions. But the scientific community came to crave a more complex version of BECs compiled of molecules, albeit with no avail.

Finally, in 2008, the first breakthrough came when a duo of physicists chilled a gas of potassium-rubidium molecules to about 350 nanoKelvin. The quest for achieving an even lower temperature to cross the BEC threshold continued.

Microwaves: The chilling solution

In 2023, the initial step towards this goal was achieved when the research group created their desired ultracold sodium-cesium molecule gas using a blend of laser cooling and magnetic manipulations. To further decrease the temperature, they decided to introduce microwaves.

Microwaves can construct small shields around each molecule, preventing them from colliding and leading to a drop in the overall temperature of the sample.

Propelling into quantum control era

The group’s achievement of creating a molecular BEC represents a spectacular accomplishment in quantum control technology.

This brilliant piece of scientific work is bound to impact a multitude of scientific fields, from the study of quantum chemistry to the exploration of complex quantum materials.

“We really have a thorough understanding of the interactions in this system, which is vital for the subsequent steps, like exploring dipolar many-body physics,” said co-author and Columbia postdoc Ian Stevenson.

The research team developed schemes to control interactions, tested these from a theoretical angle, and executed them in the actual experiment. It’s truly wondrous to witness the realization of these microwave ‘shielding’ concepts in the lab.

Unfurling a new canvas in quantum physics

The creation of molecular BECs enables the fulfilment of numerous theoretical predictions. The stable nature of these molecular BECs allows extensive exploration of quantum physics.

A proposition to build artificial crystals with BECs held in a laser-made optical lattice might provide a comprehensive simulation of interactions in natural crystals.

On switching from a three-dimensional system to a two-dimensional one, new physics is expected to emerge. This area of research opens up a plethora of possibilities in the study of quantum phenomena, including superconductivity and superfluidity, amongst others.

“This feels like a whole new universe of possibilities unveiling itself,” Sebastian Will concluded, summing up the enthusiasm in the scientific community.

BECs: From atoms to molecules

In summary, this research chronicles the successful creation of a Bose-Einstein Condensate (BEC) using ultracold sodium-cesium molecules, reaching a stable state at five nanoKelvin for two seconds.

Leveraging a combination of laser cooling, magnetic manipulations, and innovative microwave shielding, the research group and their theoretical collaborator achieved unprecedented control over molecular interactions at quantum levels.

This milestone enables comprehensive exploration of quantum phenomena such as coherence, phase transitions, and many-body interactions, potentially unlocking new avenues in quantum simulations, quantum computing, and precision measurements.

The full study was published in the journal Nature.

Special thanks to Ellen Neff from Columbia University.

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