Coherent quantum state storage and transfer between two phase qubits via a resonant cavity

Area of Science:

• Quantum Information Science
• Superconducting Quantum Computing
• Quantum Communication

Background:

• Quantum information processors require addressable qubits, memory, and a quantum communication bus.
• Superconducting qubits are promising for large-scale quantum processors but lack demonstrated quantum bus communication.
• Previous experiments showed coherent coupling for up to four qubits.

Purpose of the Study:

• To demonstrate coherent quantum state transfer between two superconducting qubits via a quantum bus.
• To investigate the potential of superconducting cavities as quantum memory elements.

Main Methods:

• Utilized two superconducting Josephson phase qubits.
• Employed a resonant cavity formed by an open-ended superconducting transmission line as a quantum bus.
• Prepared an initial quantum state, transferred it through the cavity, and retrieved it with the second qubit.

Main Results:

• Successfully demonstrated coherent transfer of quantum states between two superconducting qubits through the quantum bus.
• Showcased the transfer of quantum information into a nonclassical photon state within the cavity.
• Indicated that high-quality superconducting cavities can serve as short-term quantum memory.

Conclusions:

• The developed architecture enables coherent quantum state transfer between superconducting qubits.
• This work is a critical step towards building scalable quantum information processors.
• The findings suggest potential for advanced quantum communication and memory applications using superconducting circuits.