Generation of Fully Phase-Controlled Two-Photon Entangled States

Phys. Rev. Lett. 137, 103604 (2026) · DOI: 10.1103/4gnb-y56d · arXiv: 2601.16875

License: CC BY 4.0.

Abstract

Control over the internal states of trapped ions makes them the ideal system to generate single and two-photon states. Coupling a single ion to an optical cavity enables efficient emission of single photons into a single spatial mode and grants control over their temporal shape, phase, and frequency. Using the long coherence time of the ion’s internal states and employing a scheme to protect the coherence of the ion-cavity interaction, we demonstrate the generation of a two-photon entangled state with full control over the phase. Initially, ion-photon entanglement is generated. A second photon is subsequently generated, mapping the ion’s state onto the second photon. By adjusting the drive field the phase of the entangled state can be fully controlled. We implement this scheme in the most resource efficient way by utilizing a single ⁴⁰Ca⁺ ion coupled to an optical cavity and demonstrate the generation of a two-photon entangled stated with full phase control with a fidelity of up to 82%.

Figures

5 panels with data across 2 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

Illustrative figure, no extractable data. Shown in the paper PDF. Page 1 of the PDF.

Fig. 2

Illustrative figure, no extractable data. Shown in the paper PDF. Page 2 of the PDF.

Fig. 3

• panel (1): Photon Amplitude against arrival time ($\mu$s) for the two polarization channels, Detector 1 and Detector 2, with error bars. The dashed line separates the Photon 1 window (left) from the Photon 2 window (right). The solid curves are Gaussian fits to each window made for this panel; the caption does not name the printed curves. data.csv

Fig. 4

• panel (a): Detection Probability of the twelve detection outcomes, HH to LL, for the $|\Psi^-\rangle$ Bell state, as three bar series, one per measurement basis: XX (H/V), YY (D/A) and ZZ (R/L), with error bars. The black outline of the perfect Bell state in the print is not drawn, and the gaps between the three groups of bars are not reproduced. data.csv
• panel (b): Detection Probability of the twelve detection outcomes, HH to LL, for the $|\Psi^+\rangle$ Bell state, as three bar series, one per measurement basis: XX (H/V), YY (D/A) and ZZ (R/L), with error bars. The black outline of the perfect Bell state in the print is not drawn, and the gaps between the three groups of bars are not reproduced. data.csv
• panel (c): Contrast measurement in the X basis: $\langle XX\rangle$ against phase (degrees) as the phase is scanned, with error bars. The black curve is a fit of the caption's form $A \sin(x + \phi)$ to these points, made for this panel in place of the printed fit. data.csv
• panel (d): Contrast measurement in the X basis: $\langle XX\rangle$ against phase (degrees) as the phase is scanned, with error bars. The black curve is a fit of the caption's form $A \sin(x + \phi)$ to these points, made for this panel in place of the printed fit. data.csv

Cite

Ian Ford, Adrien Amour, Matthias Keller. Generation of Fully Phase-Controlled Two-Photon Entangled States. Phys. Rev. Lett. 137, 103604 (2026). https://doi.org/10.1103/4gnb-y56d

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