Logical states for fault-tolerant quantum computation with propagating light.

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum Error Correction

Background:

• Quantum computing requires robust quantum information encoding for error correction.
• The Gottesman-Kitaev-Preskill (GKP) qubit is a leading candidate for quantum error correction.
• Previous GKP qubit demonstrations were limited to mechanical and microwave frequencies.

Purpose of the Study:

• To realize a GKP qubit state in propagating light at telecommunication wavelengths.
• To verify the GKP state using homodyne measurements without loss corrections.
• To establish a foundation for quantum computation with light.

Main Methods:

• Generation of GKP states through the interference of cat states.
• Verification of GKP states using homodyne measurements.
• Characterization of nonclassicality and non-Gaussianity in the generated states.

Main Results:

• Successfully realized GKP states in propagating light at telecommunication wavelengths.
• Verified GKP states via homodyne measurements, demonstrating nonclassicality and non-Gaussianity.
• Observed characteristic trident shapes in faint GKP state instances.

Conclusions:

• This work presents the first optical-frequency GKP qubit, a significant step for quantum error correction.
• The demonstrated method provides a pathway for developing brighter, multi-peaked GKP qubits.
• This advancement is crucial for enabling practical quantum computation with light.