Stabilization and operation of a Kerr-cat qubit

Area of Science:

• Quantum Information Science
• Superconducting Circuits
• Quantum Optics

Background:

• Schrödinger cat states, quantum superpositions of distinct classical states, are crucial for quantum metrology, communication, and computation.
• Encoding qubits in superpositions of coherent states offers protection against phase-flip errors, but practical implementation faces challenges in state stabilization and fast control.

Purpose of the Study:

• To experimentally demonstrate a method for generating and stabilizing Schrödinger cat states.
• To improve the robustness and control of error-protected qubits encoded in these states.

Main Methods:

• Utilized the interplay between Kerr nonlinearity and single-mode squeezing in a superconducting microwave resonator.
• Implemented stabilization techniques to maintain the integrity of highly excited Schrödinger cat states.

Main Results:

• Achieved a significant increase (over one order of magnitude) in the transverse relaxation time of the stabilized qubit compared to single-photon Fock-state encoding.
• Demonstrated single-qubit gate operations on timescales over sixty times faster than the shortest coherence time.
• Successfully performed single-shot readout of the protected qubit under stabilization.

Conclusions:

• The demonstrated method effectively generates and stabilizes Schrödinger cat states, enhancing qubit coherence and enabling fast quantum control.
• These stabilized macroscopic states offer a promising platform for robust quantum information processing, combining speed and error resilience.