Direct observation of second-order atom tunnelling.

Area of Science:

• Quantum physics
• Atomic physics
• Condensed matter physics

Background:

• Quantum tunneling is a fundamental phenomenon where particles pass through classically forbidden barriers.
• Interactions between particles can lead to complex dynamics, deviating from independent tunneling behavior.
• Coulomb blockade in electronic systems demonstrates how particle interactions influence tunneling.

Purpose of the Study:

• To directly observe and characterize the correlated tunneling of two interacting ultracold atoms.
• To investigate the influence of inter-atomic interactions on tunneling dynamics in a double-well potential.
• To explore novel quantum phenomena arising from particle correlations during tunneling.

Main Methods:

• Time-resolved observations of ultracold atoms in a double-well potential.
• Measurement of both atom position and phase coherence over time.
• Experimental manipulation of interaction strengths between atoms.

Main Results:

• Observed independent atomic tunneling in the weak interaction regime, analogous to Josephson junctions.
• Demonstrated correlated, pair tunneling of two interacting atoms in the strong interaction regime via a second-order co-tunnelling process.
• Identified a conditional tunneling regime where a single atom's tunneling depends on the presence of a second particle.

Conclusions:

• Correlated tunneling events, particularly second-order co-tunnelling, are significant in strongly interacting ultracold atom systems.
• These findings provide direct experimental evidence for phenomena relevant to quantum magnetism and superexchange interactions.
• The study offers a new platform for exploring quantum dynamics and control in interacting many-body systems.