Photonic qubits, qutrits and ququads accurately prepared and delivered on demand

TL;DR

This paper demonstrates the deterministic generation and manipulation of photonic qubits, qutrits, and ququads with high fidelity, enabling scalable quantum information processing using narrowband photons from an atom-cavity system.

Contribution

It introduces a method to encode and prepare high-dimensional photonic states deterministically with high fidelity, advancing quantum communication and computing capabilities.

Findings

Deterministic emission of narrowband photons from an atom-cavity system.

High-fidelity encoding of qubits (>95%) verified by quantum-homodyne.

Successful subdivision into multiple time bins for encoding qudits.

Abstract

Reliable encoding of information in quantum systems is crucial to all approaches to quantum information processing or communication. This applies in particular to photons used in linear optics quantum computing (LOQC), which is scalable provided a deterministic single-photon emission and preparation is available. Here, we show that narrowband photons deterministically emitted from an atom-cavity system fulfill these requirements. Within their 500 ns coherence time, we demonstrate a subdivision into d time bins of various amplitudes and phases, which we use for encoding arbitrary qu-d-its. The latter is done deterministically with a fidelity >95% for qubits, verified using a newly developed time-resolved quantum-homodyne method.