Synopsis: Fermionic Switch

Interacting atoms mimic the behavior of identical fermions.
Synopsis figure
G. Zürn et al., Phys. Rev. Lett. (2012)

Whether particles in a many-body quantum system are bosons or fermions determines its fundamental properties. For identical fermions, the probability to occupy the same point in space has to vanish. However, simulating the emergence of this effect is challenging, since the fermionic nature of a particle can’t be slowly turned on. Now, a group in Germany has designed a cold-atom experiment where they can adjust the interactions between two distinguishable fermions so they mimic identical fermions.

Gerhard Zürn and his colleagues at Heidelberg University prepared two experiments in which an optical potential confined a pair of fermionic lithium-6 atoms in a long, cigar-shaped volume. In one experiment, the atoms were identical; in the other, the two atoms had opposite spin. The group used an external magnetic field to tune the interaction strength between the distinguishable atoms, but this field had no effect on the identical fermions.

A quirk of this one-dimensional system is that if both two-particle systems have the same energy, they must be described by the same spatial probability distribution. The authors determined the energy of each two-particle system by creating a “leak” in the optical potential and measuring the rate at which a particle tunneled out. By tuning the repulsive interaction between the distinguishable atoms, Zürn et al. were able to bring this system to a point where the probability that the particles overlap is zero, as for two identical fermions.

The ability to simulate the wave function of identical fermions in a two-particle system such as this could eventually allow the study of more complex many-bodied quantum systems. – Jessica Thomas


More Announcements »

Subject Areas

Atomic and Molecular PhysicsQuantum Physics

Previous Synopsis

Biological Physics

Double, Double…Bubble

Read More »

Next Synopsis

Particles and Fields

Going the Distance

Read More »

Related Articles

Viewpoint: New Entry in the Thermodynamic Rulebook for Quantum Systems
Quantum Physics

Viewpoint: New Entry in the Thermodynamic Rulebook for Quantum Systems

Thermodynamic laws that are unique to quantum systems in a superposition of states have been derived using an information-theory approach. Read More »

Viewpoint: Cool Physics with Warm Ions
Atomic and Molecular Physics

Viewpoint: Cool Physics with Warm Ions

Ultrafast laser pulses can be used to control and characterize the quantum motion of a single trapped ion over 5 orders of magnitude in temperature. Read More »

Synopsis: Quantum Rocking Motion in Molecular Rotors
Quantum Physics

Synopsis: Quantum Rocking Motion in Molecular Rotors

A type of quantum oscillation—known to occur for electrons in a crystal—has now been observed in a gas of molecular rotors that are spun around by laser pulses. Read More »

More Articles