Correlation between two distant quasiparticles in separate superconducting islands mediated by a single spin

Area of Science:

• Quantum physics
• Condensed matter physics
• Quantum information science

Background:

• Controlled coupling of distant quantum particles is crucial for quantum information technologies.
• Hybrid systems of quantum dots and superconducting islands offer tunable properties and macroscopic coherence.
• Electrons in quantum dots are typically screened into singlet states, hindering long-distance spin alignment.

Purpose of the Study:

• To investigate the overscreening mechanism in hybrid quantum dots.
• To demonstrate the creation of ferromagnetic correlations between superconducting islands.
• To explore a novel platform for controllable large-scale spin coupling.

Main Methods:

• Experimental realization of hybrid systems with semiconducting quantum dots and superconducting islands.
• Utilizing the overscreening effect of two quasiparticles to stabilize a doublet state.
• Proposing and investigating alternating chains of quantum dots and superconducting islands.

Main Results:

• Experimental evidence of a stabilized overscreened state in a hybrid quantum dot system.
• Demonstration of correlated quasiparticles over micrometer distances.
• Observation of ferromagnetic correlations between superconducting islands mediated by the quantum dot.

Conclusions:

• The overscreening of quantum dots by multiple quasiparticles can lead to controllable ferromagnetic correlations.
• Hybrid quantum dot-superconductor systems can overcome the limitations of electron screening for long-distance spin alignment.
• Alternating chains of quantum dots and superconducting islands represent a promising platform for scalable quantum information processing.