Scientists have produced a rare form of quantum matter known as a Bose-Einstein condensate (BEC), which uses molecules instead of atoms.
These BECs consist of cooled sodium-cesium molecules and are as cold as five nanoKelvin (approximately -459.66 °F). They remain stable for as long as two seconds.
“These molecular BECs open up new areas of research, from understanding truly fundamental physics to developing powerful quantum simulations,” noted physicist Sebastian Will of Columbia University. “We have reached an exciting milestone, but it is just the beginning.”
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 bosons are in the lowest quantum state, resulting in macroscopic quantum phenomena.
This means that they behave like a single quantum entity and actually ‘collapse’ into a single wave function that can easily be described using the principles of quantum mechanics.
The fascinating aspect of BECs comes from their superfluid properties: they exhibit zero viscosity during flow, allowing them to move without dissipating energy.
This unique property allows BECs to simulate other quantum systems and explore new areas of physics.
For example, studying BECs can provide insights into quantum coherence, phase transitions, and many-body interactions in quantum gases.
The creation of molecular BECs, such as 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 long and winding, dating back a century to the works of physicists Satyendra Nath Bose and Albert Einstein.
They predicted that a cluster of particles cooled to a standstill would coalesce into a single 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 began to yearn for a more complex version of BECs composed of molecules, although without success.
Finally, in 2008, the first breakthrough came when a pair of physicists cooled a gas of potassium-rubidium molecules to about 350 nanoKelvin. The search for an even lower temperature to exceed the BEC threshold continued.
Microwaves: the cooling solution
In 2023, the first step towards this goal was taken when the research group created their desired ultracold sodium-cesium molecular gas using a mix of laser cooling and magnetic manipulations. To further reduce the temperature, they decided to introduce microwaves.
Microwaves can create small shields around each molecule, preventing collisions and keeping the overall temperature of the sample from dropping.
Towards the age of quantum control
The group’s achievement in creating a molecular BEC is a spectacular feat in the field of quantum control technology.
This brilliant scientific work will undoubtedly have an impact on a wide range of scientific fields, from the study of quantum chemistry to the exploration of complex quantum materials.
“We really have a deep understanding of the interactions in this system, which is vital for next steps such as exploring dipolar many-body physics,” said co-author and Columbia postdoc Ian Stevenson.
The research team developed schemes to control interactions, tested them from a theoretical perspective, and implemented them in the actual experiment. It is truly amazing to witness the realization of these microwave “shielding” concepts in the laboratory.
Unfolding a new canvas in quantum physics
The creation of molecular BECs allows the fulfillment of numerous theoretical predictions. The stable nature of these molecular BECs enables extensive exploration of quantum physics.
A proposal to build artificial crystals with BECs in a laser-made optical lattice could provide a comprehensive simulation of interactions in natural crystals.
When moving from a three-dimensional system to a two-dimensional system, 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.
“This feels like a whole new universe of possibilities unfolding,” Sebastian Will concluded, summing up the excitement in the scientific community.
BECs: from atoms to molecules
In summary, this study describes the successful creation of a Bose-Einstein condensate (BEC) using ultracold sodium-cesium molecules, achieving a steady state at five nanoKelvin for two seconds.
By using 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 the quantum level.
This milestone enables a comprehensive exploration of quantum phenomena such as coherence, phase transitions and many-body interactions, potentially opening up new avenues in quantum simulations, quantum computing and precision measurements.
The full study was published in the journal Nature.
Special thanks to Ellen Neff of Columbia University.
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