Experimental realization of on-chip few-photon control around exceptional points

Area of Science:

• Quantum Physics
• Condensed Matter Physics
• Superconducting Circuits

Background:

• Non-Hermitian systems exhibit unique properties near exceptional points (EPs), where eigenvalues and eigenstates coalesce.
• Phase transitions in these systems can lead to phenomena like unidirectional wave transmission.
• Extending these properties to the quantum regime remains an active area of research.

Purpose of the Study:

• To investigate quantum phase transitions and exceptional points in non-Hermitian systems.
• To demonstrate unidirectional microwave transmission in the quantum regime.
• To explore potential applications in quantum devices.

Main Methods:

• Utilized a non-Hermitian on-chip superconducting quantum circuit.
• Observed phase transitions and exceptional points.
• Demonstrated unidirectional microwave transmission in the few-photon regime.

Main Results:

• Successfully observed a phase transition and its associated exceptional point in the superconducting circuit.
• Achieved unidirectional microwave transmission even in the few-photon regime.
• The broken symmetry phase near the exceptional point facilitates this unidirectional transmission.

Conclusions:

• This study confirms the existence of quantum phase transitions and exceptional points in non-Hermitian superconducting circuits.
• Unidirectional microwave transmission is achievable at the quantum level, opening possibilities for few-photon devices.
• Non-Hermitian systems offer a promising platform for fundamental physics exploration and practical quantum device development.