In 2018, Kang-Kuen Ni and her lab, with an impressive feat, earned the cover of Science magazine: they took two separate atoms, sodium and caesium, and forged them into one dipole, sodium caesium.
Sodium and caesium usually ignore each other in the wild; but in the lab's carefully calibrated vacuum chamber, she and her team captured each atom with lasers and then made them react, an ability that gave scientists a new method to study one of the most basic and ubiquitous processes on Earth: the formation of a chemical bond. With Ni's invention, scientists could not only learn more about our chemical foundations, but they could also start creating custom-made molecules for new applications, like qubits for quantum computers.
But there was one flaw in their original sodium caesium molecule: "This molecule was lost soon after it was made," said Ni, Morris Kahn associate professor of chemistry and chemical biology and physics. Now, in a new study published in Physics Review Letters, Ni and her team report a new feat: they gave their molecule a long lifespan of up to almost three and a half seconds – a luxury of time in the quantum realm-by controlling all the degrees of freedom (including its motion) of a single dipole molecule for the first time. During these precious seconds, researchers can maintain the full quantum control needed for stable qubits, the building blocks for a wide range of interesting quantum applications.
According to the paper, " these long-term, fully quantum states of controlled individual dipole molecules provide a key resource for molecule-based quantum modeling and information processing." For example, such molecules can accelerate progress towards quantum modeling of new phases of matter (faster than any known computer), high-precision quantum information processing, precision measurements, and fundamental research in cold chemistry (one of Ni's specialties).
And by forming docile molecules in their quantum states of the earth (basically, their simplest, most malleable form), the researchers have created more robust qubits with electric knobs that, like the magnetic knobs of a magnet, allow researchers to interact with them in new ways (such as with microwave and electric fields).
Next, the team works on scaling its process: they plan to assemble not just one molecule from two atoms but to force large collections of atoms to interact and form molecules in parallel. In doing so, they can also begin to perform long-term entanglement interactions between molecules, the basis for information transfer in quantum computing.
"With the addition of a microwave oven and electric field control," Ni said, " molecular qubits for quantum computing applications and simulations that further our understanding of the quantum phases of matter are within experimental reach."