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Fiber-Based Frequency Conversion of Single Photons via Intermodal Four-Wave Mixing

Thjalfe Ulvenberg, Kasper Alexander, Paweł Wyborski, Claudia Piccinini, Niels Gregersen, Battulga Munkhbat, Michael Galili, Lars Søgaard Rishøj, Karsten K. Rottwitt

Published Jan 1, 2025• 0 citations
Publisher

Abstract

Using intermodal four-wave mixing in an optical step-index fiber, we demonstrate tunable low-noise frequency conversion of single photons emitted from a InAs/GaAs quantum dot with peak conversion efficiency of -0.6 dB.
DOI
10.1364/cleo_fs.2025.ff107_3

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Optical frequency conversion plays a key role in realizing large-scale quantum networks, including multi-qubit discrete-variable quantum computers and quantum communication links where photons serve as the fundamental qubits. However, achieving efficient conversion via nonlinear optical processes for specific target wavelengths remains a significant challenge, as precise dispersion control is essential to satisfy phase-matching conditions across specific frequency ranges. An intriguing approach to solve this challenge is leveraging the modal degree of freedom in spatially multimoded waveguides and realizing intermodal nonlinear interaction. Following this approach, we present the experimental demonstration of tunable, number-state-preserving frequency conversion of true single photons emitted from a quantum dot. The conversion is achieved in a multimode fiber and exhibits a peak internal efficiency of 85% while retaining single photon purity of 99% during conversion. Our results show that the intermodal platform presents a promising and versatile approach for overcoming phase-matching limitations in quantum frequency conversion, thus allowing the efficient interfacing of different optical quantum devices.
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Large-scale quantum networks comprise various components such as photon sources and transmission lines, which operate at diverse wavelengths. The optimal transmission window through solid silica optical fibre is around 1.55 μm while efficient single-photon sources based on InAs quantum dots (QDs) operate in the range of 900–950 nm [1]. High indistinguishability between photons is also required to realise many quantum information technologies but any two dots seldom emit at the same exact wavelength [2] and sending photons through a quantum network may distort their spectra. Parametric nonlinear processes, such as Bragg-Scattering four wave mixing (BS-FWM), enable frequency conversion of photons while preserving their quantum properties [3],[4].