Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optics Express

Efficient quantum frequency conversion for networking on the telecom E-band

S. M. Patomäki, Maxim A. Sirotin, Dirk Englund, Franco N. C. Wong

Published Feb 2, 2026• 0 citations
Publisher

Abstract

High-efficiency quantum frequency conversion (QFC) for group-IV color centers, such as silicon vacancies (SiV), is required for long-distance quantum networking protocols. Performance of QFC depends on the choices of network and pump wavelengths and the choice between bulk crystal and waveguide, since these directly determine the dominant noise processes. These furthermore lead to fiber-based or free-space, single- or multi-pass setups with different complexities, power requirements, losses, and hence, external efficiencies. Here, we present a QFC device design for SiV QFC with simultaneous state-of-the-art performance and simple setup. Namely, by choosing the C-band pump wavelength of λ p = 1561 nm, which leads to an E-band network wavelength of λ n = 1398 nm, we remain in the anti-Stokes noise regime in a one-stage, single-pass conversion scheme. The high-quality erbium-doped fiber amplifiers in this band aid in maximizing the internal nonlinear process. We measure an external (internal) photon conversion efficiency of 44.5 ± 1.8 % (8.5 ± 1.8 %) at an external (internal) pump power of 1.51 W (0.97 W), limited by fiber coupling efficiencies. This is an increase in efficiency by 9 % (25 %) compared to prior demonstrations for SiV QFC, which were limited by factors such as internal device efficiencies, limited available pump power, and losses. We measure a pump-generated noise spectral density of 4913 counts/s/nm, which can be attributed to the anti-Stokes Raman scattering, in line with other one-stage demonstrations, though higher by an order of magnitude than that obtained in two-stage conversion. Without extra filtering, we expect this to lead to a networking photon signal-to-noise ratio of above 7000 for cavity-integrated SiVs in emission-based schemes.

DOI
10.1364/oe.583551

Related papers

Quantum frequency conversion for networking via the telecom E-band

Sofia Patomäki, S. M. Patomäki, Maxim A. Sirotin +3 more

High-efficiency quantum frequency conversion (QFC) for group-IV color centers, such as silicon vacancies (SnV), is required for long-distance quantum networking protocols. SiV QFC has previously been demonstrated at external eGiciencies of 12% [1] and 30% [2], using periodically poled lithium niobate (PPLN) waveguides of lengths 3.5 and 5 mm, and with eGiciencies limited by the available pump power (120 mW and 320 mW, respectively). Here, the eGiciency scales with the square of the waveguide length. These results are also obtained with pump wavelength of 1623 nm (L-band), networking the SiV wavelength of 737 nm into the O-band (1350 nm). Here, we improve these results by replacing the pump (L-band in [1],[2]) with a pump with wavelength in the C-band (1561 nm), where (i) high-power erbium-doped fiber amplifiers (EDFAs) are available (ii) SMF-28e fibers have lower losses in the E-band than O-band. Using an EDFA and a 1.5-cm-long PPLN waveguide We measure a maximum external photon conversion eGiciency of 43±1.8% (corresponding internal eGiciency of 96±1.8%), which we reach at an external pump power of 1.51 W. The external eGiciency is limited by waveguide-fiber coupling. As such, we have demonstrated an external eGiciency for SiV-telecom quantum frequency conversion exceeding prior results from MIT, Lincoln Labs, and Harvard. To further improve these results in the future, the waveguide will be replaced with a longer one to reduce the power required to reach unit internal eGiciency, which further reduces noise. We may also optimize fiber coupling or switch to a free-space-coupled device, which we estimate to increase the external conversion eGiciency to approx. 70-80%.

•Jan 1, 2025•0 citations

Fiber-integrated Quantum Frequency Conversion for Long-distance Quantum Networking

Zhichuan Liao, Ao Shen, Lai Zhou +2 more

Signal photons emitted by quantum nodes typically fall outside the low-loss telecom window of optical fibers, leading to severe transmission losses. Quantum frequency conversion (QFC) offers an effective optical interface that bridges quantum nodes with telecom-band channels, enabling long-distance quantum communication. In this work, we demonstrate a compact, fiber-integrated QFC system with low noise and a high signal-to-noise ratio (SNR). Using a periodically poled lithium niobate (PPLN) waveguide, input photons at 637.2 nm are down-converted to telecom photons at 1588.3 nm. Our system achieves a total conversion efficiency of approximately 9%, with pump-induced noise suppressed to 154 Hz. For input photon rates of 32.7, 118.0, and 327.7 kHz, the corresponding SNRs are 12.3, 43.9, and 117.8, respectively. We further develop a theoretical model to simulate the entanglement fidelity between nitrogen-vacancy (NV) center spins and the frequency-converted telecom photons. At the emission rate of an NV center, our QFC system maintains an expected fidelity exceeding 52% over a transmission distance of 100 km. These findings highlight the potential of our QFC system for scalable, long-distance quantum networking.

quant-pharXiv:2604.23444•npj Quantum Information•Apr 28, 2026•0 citations

Two-stage, low noise quantum frequency conversion of single photons from silicon-vacancy centers in diamond to the telecom C-band

Marlon Schäfer, Benjamin Kambs, Dennis Herrmann +2 more

The silicon-vacancy center in diamond holds great promise as a qubit for quantum communication networks. However, since the optical transitions are located within the visible red spectral region, quantum frequency conversion to low-loss telecommunication wavelengths becomes a necessity for its use in long-range, fiber-linked networks. This work presents a highly efficient, low-noise quantum frequency conversion device for photons emitted by a silicon-vacancy (SiV) center in diamond to the telecom C-band. By using a two-stage difference-frequency mixing scheme SPDC noise is circumvented and Raman noise is minimized, resulting in a very low noise rate of $10.4 \pm 0.7$ photons per second as well as an overall device efficiency of $35.6\, \%$. By converting single photons from SiV centers we demonstrate the preservation of photon statistics upon conversion.

arXiv:2307.11389•Jul 21, 2023•0 citations

Efficient bidirectional quantum frequency conversion between telecom and visible bands using adaptively phase-matched III-V nanophotonic waveguides

Jierui Hu, Hao Yuan, Joshua Akin +3 more

Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional QFC between the telecom (1550-nm) and visible (780-nm) bands using unpoled indium gallium phosphide (InGaP) χ(2) nanophotonic waveguides, eliminating the need for a long-wavelength pump. Leveraging the large nonlinear susceptibility of InGaP together with adaptive phase-matching control, we obtain 27% (55%) internal efficiency in a 6-mm (2.5-mm)-long waveguide with a low pump power of 20 mW (50 mW) and a noise flux spectral density of 10−4 counts per second per hertz at signal–pump detuning of 20 nm. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks. Future quantum networks need low-noise frequency conversion. This work tackles pump-noise and phase-matching limits by using adaptively phase-matched InGaP χ(2) nanowaveguides to efficiently convert telecom and 780 nm light while preserving quantum characteristics.

Nature Communications•Apr 8, 2026•2 citations

High-Performance Quantum Frequency Conversion from Ultraviolet to Telecom Band

Yi Yang, Bin Wang, Ji-Chao Lin +10 more

Quantum frequency conversion (QFC) is essential for bridging the spectral gap between stationary qubits and low-loss optical communication channels. Practicable QFC interfaces connecting ultraviolet and telecommunication bands are of great significance but have remained elusive, constrained by the dual challenges of a high-performance frequency converter and effective noise suppression in short-wavelength pumping configurations. We address this by demonstrating the phase-matching mechanism with domain defects and differential-tuning behavior of the spontaneous parametric down-conversion noises. Based on a quantitative analysis of performance degradation induced by domain defects, we propose specific fabrication guidelines and experimentally achieve an ultrahigh normalized conversion efficiency of 839%/(W cm^{2}) for the fundamental guided mode in thin-film lithium niobate waveguides. Meanwhile, we reveal a new noise control mechanism for short-wavelength pumping by utilizing the differential-tuning behaviors of difference-frequency generation and spontaneous parametric down-conversion processes. Then a single-stage QFC from 393 nm to the telecom C band with a record-high external efficiency of 28.8% and an ultralow noise level of 35 counts per second is achieved experimentally. The proposed mechanisms would enable other QFCs with higher efficiency and lower noise, advancing the development of scalable quantum networks. Furthermore, it holds significant potential for driving progress in both classical and integrated nonlinear photonics.

Physical Review Letters•Sep 1, 2026•0 citations

Quantum frequency conversion of single photons from a tin-vacancy center in diamond

Julia M. Brevoord, Jan Fabian Geus, Tim Turan +7 more

Diamond tin-vacancy (SnV) centers are promising candidates for building quantum network nodes. However, their native photon emission at 619 nm is incompatible with metropolitan-scale networks operating at low-loss telecom wavelengths. To address this, we demonstrate highly efficient, low-noise quantum frequency conversion (QFC) of 619 nm photons to the telecom S-band at 1480 nm. The conversion process combines 619 nm photons with 1064 nm pump light in an actively stabilized cavity containing a bulk monocrystalline potassium titanyl arsenate (KTA) crystal. We achieve an internal (external) conversion efficiency of (48 ± 3) % ((28 ± 2) %) and a noise photon rate per wavelength of (2.2 ± 0.9) cts/s/pm, which is spectrally flat in the investigated frequency range of 40 GHz. Furthermore, we demonstrate that the efficiency remains above 80% of its maximum over a frequency range of 70 GHz. Finally, we generate a string of photons from a single waveguide-embedded SnV − center using a train of excitation pulses and send these through the QFC. After the QFC, we observe telecom light displaying the SnV lifetime, confirming successful conversion. These results represent a critical step towards metropolitan-scale fiber-based quantum networks using SnV − centers.

Optica Quantum•Dec 10, 2025•3 citations
High-efficiency quantum frequency conversion (QFC) for group-IV color centers, such as silicon vacancies (SiV), is required for long-distance quantum networking protocols. Performance of QFC depends on the choices of network and pump wavelengths and the choice between bulk crystal and waveguide, since these directly determine the dominant noise processes. These furthermore lead to fiber-based or free-space, single- or multi-pass setups with different complexities, power requirements, losses, and hence, external efficiencies. Here, we present a QFC device design for SiV QFC with simultaneous state-of-the-art performance and simple setup. Namely, by choosing the C-band pump wavelength of λ p = 1561 nm, which leads to an E-band network wavelength of λ n = 1398 nm, we remain in the anti-Stokes noise regime in a one-stage, single-pass conversion scheme. The high-quality erbium-doped fiber amplifiers in this band aid in maximizing the internal nonlinear process. We measure an external (internal) photon conversion efficiency of 44.5 ± 1.8 % (8.5 ± 1.8 %) at an external (internal) pump power of 1.51 W (0.97 W), limited by fiber coupling efficiencies. This is an increase in efficiency by 9 % (25 %) compared to prior demonstrations for SiV QFC, which were limited by factors such as internal device efficiencies, limited available pump power, and losses. We measure a pump-generated noise spectral density of 4913 counts/s/nm, which can be attributed to the anti-Stokes Raman scattering, in line with other one-stage demonstrations, though higher by an order of magnitude than that obtained in two-stage conversion. Without extra filtering, we expect this to lead to a networking photon signal-to-noise ratio of above 7000 for cavity-integrated SiVs in emission-based schemes.
High-efficiency quantum frequency conversion (QFC) for group-IV color centers, such as silicon vacancies (SnV), is required for long-distance quantum networking protocols. SiV QFC has previously been demonstrated at external eGiciencies of 12% [1] and 30% [2], using periodically poled lithium niobate (PPLN) waveguides of lengths 3.5 and 5 mm, and with eGiciencies limited by the available pump power (120 mW and 320 mW, respectively). Here, the eGiciency scales with the square of the waveguide length. These results are also obtained with pump wavelength of 1623 nm (L-band), networking the SiV wavelength of 737 nm into the O-band (1350 nm). Here, we improve these results by replacing the pump (L-band in [1],[2]) with a pump with wavelength in the C-band (1561 nm), where (i) high-power erbium-doped fiber amplifiers (EDFAs) are available (ii) SMF-28e fibers have lower losses in the E-band than O-band. Using an EDFA and a 1.5-cm-long PPLN waveguide We measure a maximum external photon conversion eGiciency of 43±1.8% (corresponding internal eGiciency of 96±1.8%), which we reach at an external pump power of 1.51 W. The external eGiciency is limited by waveguide-fiber coupling. As such, we have demonstrated an external eGiciency for SiV-telecom quantum frequency conversion exceeding prior results from MIT, Lincoln Labs, and Harvard. To further improve these results in the future, the waveguide will be replaced with a longer one to reduce the power required to reach unit internal eGiciency, which further reduces noise. We may also optimize fiber coupling or switch to a free-space-coupled device, which we estimate to increase the external conversion eGiciency to approx. 70-80%.
Signal photons emitted by quantum nodes typically fall outside the low-loss telecom window of optical fibers, leading to severe transmission losses. Quantum frequency conversion (QFC) offers an effective optical interface that bridges quantum nodes with telecom-band channels, enabling long-distance quantum communication. In this work, we demonstrate a compact, fiber-integrated QFC system with low noise and a high signal-to-noise ratio (SNR). Using a periodically poled lithium niobate (PPLN) waveguide, input photons at 637.2 nm are down-converted to telecom photons at 1588.3 nm. Our system achieves a total conversion efficiency of approximately 9%, with pump-induced noise suppressed to 154 Hz. For input photon rates of 32.7, 118.0, and 327.7 kHz, the corresponding SNRs are 12.3, 43.9, and 117.8, respectively. We further develop a theoretical model to simulate the entanglement fidelity between nitrogen-vacancy (NV) center spins and the frequency-converted telecom photons. At the emission rate of an NV center, our QFC system maintains an expected fidelity exceeding 52% over a transmission distance of 100 km. These findings highlight the potential of our QFC system for scalable, long-distance quantum networking.
The silicon-vacancy center in diamond holds great promise as a qubit for quantum communication networks. However, since the optical transitions are located within the visible red spectral region, quantum frequency conversion to low-loss telecommunication wavelengths becomes a necessity for its use in long-range, fiber-linked networks. This work presents a highly efficient, low-noise quantum frequency conversion device for photons emitted by a silicon-vacancy (SiV) center in diamond to the telecom C-band. By using a two-stage difference-frequency mixing scheme SPDC noise is circumvented and Raman noise is minimized, resulting in a very low noise rate of 10.4±0.710.4 \pm 0.710.4±0.7 photons per second as well as an overall device efficiency of 35.6 %35.6\, \%35.6%. By converting single photons from SiV centers we demonstrate the preservation of photon statistics upon conversion.
Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional QFC between the telecom (1550-nm) and visible (780-nm) bands using unpoled indium gallium phosphide (InGaP) χ(2) nanophotonic waveguides, eliminating the need for a long-wavelength pump. Leveraging the large nonlinear susceptibility of InGaP together with adaptive phase-matching control, we obtain 27% (55%) internal efficiency in a 6-mm (2.5-mm)-long waveguide with a low pump power of 20 mW (50 mW) and a noise flux spectral density of 10−4 counts per second per hertz at signal–pump detuning of 20 nm. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks. Future quantum networks need low-noise frequency conversion. This work tackles pump-noise and phase-matching limits by using adaptively phase-matched InGaP χ(2) nanowaveguides to efficiently convert telecom and 780 nm light while preserving quantum characteristics.
Quantum frequency conversion (QFC) is essential for bridging the spectral gap between stationary qubits and low-loss optical communication channels. Practicable QFC interfaces connecting ultraviolet and telecommunication bands are of great significance but have remained elusive, constrained by the dual challenges of a high-performance frequency converter and effective noise suppression in short-wavelength pumping configurations. We address this by demonstrating the phase-matching mechanism with domain defects and differential-tuning behavior of the spontaneous parametric down-conversion noises. Based on a quantitative analysis of performance degradation induced by domain defects, we propose specific fabrication guidelines and experimentally achieve an ultrahigh normalized conversion efficiency of 839%/(W cm^{2}) for the fundamental guided mode in thin-film lithium niobate waveguides. Meanwhile, we reveal a new noise control mechanism for short-wavelength pumping by utilizing the differential-tuning behaviors of difference-frequency generation and spontaneous parametric down-conversion processes. Then a single-stage QFC from 393 nm to the telecom C band with a record-high external efficiency of 28.8% and an ultralow noise level of 35 counts per second is achieved experimentally. The proposed mechanisms would enable other QFCs with higher efficiency and lower noise, advancing the development of scalable quantum networks. Furthermore, it holds significant potential for driving progress in both classical and integrated nonlinear photonics.
Diamond tin-vacancy (SnV) centers are promising candidates for building quantum network nodes. However, their native photon emission at 619 nm is incompatible with metropolitan-scale networks operating at low-loss telecom wavelengths. To address this, we demonstrate highly efficient, low-noise quantum frequency conversion (QFC) of 619 nm photons to the telecom S-band at 1480 nm. The conversion process combines 619 nm photons with 1064 nm pump light in an actively stabilized cavity containing a bulk monocrystalline potassium titanyl arsenate (KTA) crystal. We achieve an internal (external) conversion efficiency of (48 ± 3) % ((28 ± 2) %) and a noise photon rate per wavelength of (2.2 ± 0.9) cts/s/pm, which is spectrally flat in the investigated frequency range of 40 GHz. Furthermore, we demonstrate that the efficiency remains above 80% of its maximum over a frequency range of 70 GHz. Finally, we generate a string of photons from a single waveguide-embedded SnV − center using a train of excitation pulses and send these through the QFC. After the QFC, we observe telecom light displaying the SnV lifetime, confirming successful conversion. These results represent a critical step towards metropolitan-scale fiber-based quantum networks using SnV − centers.