Cooling and Autonomous Feedback in a Bose-Hubbard Chain with Attractive Interactions

Area of Science:

• Quantum physics
• Condensed matter physics
• Superconducting circuits

Background:

• Bose-Hubbard models describe interacting bosons on a lattice.
• Controlling quantum states in such systems is crucial for quantum technologies.
• Previous methods struggled with efficient cooling and dark state preparation.

Purpose of the Study:

• To engineer a quantum bath for entropy and energy exchange with a 1D Bose-Hubbard lattice.
• To achieve efficient cooling and particle number-preserving state preparation.
• To demonstrate autonomous feedback for stabilizing quantum eigenstates.

Main Methods:

• Implementation using an array of three superconducting transmon qubits coupled to a cavity mode.
• Utilizing the transmon qubits as lattice sites and excitation quanta as bosonic particles.
• Applying continuous microwave radiation for autonomous feedback control.

Main Results:

• Successful engineering of a quantum bath enabling controlled interactions.
• Demonstration of particle number-preserving cooling, realizing a canonical ensemble.
• Efficient preparation of dark states not accessible via coherent drives.
• Indefinite stabilization of specific array eigenstates using autonomous feedback.

Conclusions:

• The developed quantum bath is a powerful tool for controlling quantum many-body systems.
• This approach offers new pathways for quantum simulation and quantum information processing.
• The demonstrated feedback mechanism provides robust stabilization of quantum states.