Fully Arbitrary Control of Frequency-Bin Qubits

Abstract

Accurate control of two-level systems is a longstanding problem in quantum mechanics. One such quantum system is the frequency-bin qubit: a single photon existing in superposition of two discrete frequency modes. %and a potential building block for scalable, fiber-compatible quantum information processing. In this work, we demonstrate fully arbitrary control of frequency-bin qubits in a quantum frequency processor for the first time. We numerically establish optimal settings for multiple configurations of electro-optic phase modulators and pulse shapers, experimentally confirming near-unity mode-transformation fidelity for all fundamental rotations. Performance at the single-photon level is validated through the rotation of a single frequency-bin qubit to 41 points spread over the entire Bloch sphere, as well as tracking of the state path followed by the output of a tunable frequency beamsplitter, with Bayesian tomography confirming state fidelities ${\mathcal{F}}_{\rho }>0.98$ for all cases. Such high-fidelity transformations expand the practical potential of frequency encoding in quantum communications, offering exceptional precision and low noise in general qubit manipulation.

9 pages, 7 figures

References in corpus (5)

• Optical frequency comb technology for ultra-broadband radio-frequency photonics
• Frequency-encoded photonic qubits for scalable quantum information processing
• Quantum Frequency Translation of Single-Photon States in Photonic Crystal Fiber
• Electro-Optic Modulation of Single Photons
• High-dimensional frequency-bin entangled photons in an optical microresonator on a chip