Understanding Quasiparticles

A quasiparticle is a concept of a state or phenomena that occurs in many-body systems or solid-state materials — like when an electron moves through a solid and polarizes its environment, generating a "polarization cloud" that moves together with the electron. This "dressed electron" is a quasiparticle also known as a polaron.

Scientists have been struggling to actually observe and measure quasiparticles. "The nonequilibrium dynamics of many-body quantum systems are tricky to study experimentally or theoretically," according to a study published in Science by a team of theoretical physicists led by Rudolf Grimm.

"These processes last only attoseconds, which makes a time-resolved observation of their formation extremely difficult," Grimm explains. An attosecond is one-quintillionth of a second — that's very fast.

Fermi polaron. Credits: MIT-Harvard, CUA

The researchers were able to create an environment that slowed the process down a bit, enabling them to observe the birth of an actual quasiparticle called a Fermi polaron (essentially, potassium atoms embedded in a lithium cloud).

To do so, they created an ultracold quantum gas, made up of lithium atoms and a small sample of potassium atoms in the middle, using laser trapping techniques inside a vacuum chamber. Then, they applied magnetic fields to tune particle interactions that formed the Fermi polaron.

The Future of Electronics

Now that a quasiparticle has been observed in real time, the next step is to actually measure it. That remains to be a challenge. However, this development is a step towards making actual quantum processors, a feat that continues to elude many quantum computation researchers.

"We developed a new method for observing the 'birth' of a polaron virtually in real time," says Grimm. Looking into the future, he says: "This may turn out to be a very interesting approach to better understand the quantum physical properties of ultrafast electronic devices."

This major breakthrough in physics could lead to huge leaps in quantum computing and ultra-fast electronics.

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