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

Quantum frequency conversion for networking via the telecom E-band

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

Published Jan 1, 2025• 0 citations
Publisher

Abstract

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%.

DOI
10.1364/cleo_si.2025.ss115_2

Related papers

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

S. M. Patomäki, Maxim A. Sirotin, Dirk Englund +1 more

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.

Optics Express•Feb 2, 2026•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

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. In this work, we demonstrate a short-wavelength-pumping QFC with the first-order quasi-phase matching period of 3.07 um on thin-film lithium niobate, converting ultraviolet photons to the telecom C-band. By constructing a theoretical model that correlates the normalized conversion efficiency with domain defects in the short-period phase-matched waveguide, we found the critical tolerance of domain defects along the waveguide should be $\le 2$ (excluding the ends). Based on this, we achieved a theoretical limit normalized conversion efficiency of 839%/(W*cm^2) for the fundamental guided mode through fabrication optimization. Furthermore, we propose a robust noise suppression strategy for short-wavelength pumping by utilizing the counter-tuning behaviors of difference-frequency generation and spontaneous parametric down-conversion. By combining these advances with ultra-narrowband filtering, we achieve a record-high external efficiency of 28.8% and an ultra-low noise of 35 counts per second. This high-performance QFC connecting ultraviolet and telecom bands satisfies the stringent requirements for long-lived remote ion-ion entanglement in scalable quantum networks [W.-Z. Liu et al., Nature (2026)].

quant-pharXiv:2603.01745•Mar 3, 2026•1 citation

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

Proposal for noise-free visible-telecom quantum frequency conversion through third-order sum and difference frequency generation

Xiyuan Lu, Gregory T. Moille, Ashutosh Rao +1 more

Quantum frequency conversion (QFC) between the visible and telecom is a key to connect quantum memories in fiber-based quantum networks. Current methods for linking such widely separated frequencies, such as sum/difference frequency generation and four-wave mixing Bragg scattering, are prone to broadband noise generated by the pump laser(s). To address this issue, we propose to use third-order sum/difference frequency generation (TSFG/TDFG) for an upconversion/downconversion QFC interface. In this process, two long wavelength pump photons combine their energy and momentum to mediate frequency conversion across the large spectral gap between the visible and telecom bands, which is particularly beneficial from the noise perspective. We show that waveguide-coupled silicon nitride microring resonators can be designed for efficient QFC between 606 and 1550 nm via a 1990 nm pump through TSFG/TDFG. We simulate the device dispersion and coupling, and from the simulated parameters, estimate that the frequency conversion can be efficient (${\gt}80 \%$) at 50 mW pump power. Our results suggest that microresonator TSFG/TDFG is promising for compact, scalable, and low-power QFC across large spectral gaps.

arXiv:2010.06811•Optics Letters•Dec 7, 2020•11 citations

Efficient C-band single-photon upconversion with chip-scale Ti-indiffused pp-LiNbO3 waveguides

Zhenda Xie, Kai Luo, Kai-Chi Chang +4 more

Frequency upconversion for single photons at telecom wavelengths is important to simultaneously meet the different wavelength requirements for long-distance communications and quantum memories in a quantum nodal network. It also enables the detection for the telecom "flying qubit" photons with silicon-based efficient single-photon detectors with low dark count (DC) rates. Here, we demonstrate the frequency upconversion of attenuated single photons, using a low-loss titanium-indiffused periodically poled lithium niobate waveguide, pumped with a readily available erbium-doped fiber amplifier in the L-band. Internal and conversion efficiencies up to 84.4% and 49.9% have been achieved, respectively. The DC rates are suppressed down to 44 kHz at 13.9% end-to-end quantum efficiency (including full conversion and detection), enabled by our long-wavelength pump configuration and narrow 3.5-GHz bandpass filtering.

Applied Optics•Jul 22, 2019•7 citations
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%.
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.
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.
Quantum frequency conversion (QFC) is essential for bridging the spectral gap between stationary qubits and low-loss optical communication channels. In this work, we demonstrate a short-wavelength-pumping QFC with the first-order quasi-phase matching period of 3.07 um on thin-film lithium niobate, converting ultraviolet photons to the telecom C-band. By constructing a theoretical model that correlates the normalized conversion efficiency with domain defects in the short-period phase-matched waveguide, we found the critical tolerance of domain defects along the waveguide should be ≤2\le 2≤2 (excluding the ends). Based on this, we achieved a theoretical limit normalized conversion efficiency of 839%/(W*cm^2) for the fundamental guided mode through fabrication optimization. Furthermore, we propose a robust noise suppression strategy for short-wavelength pumping by utilizing the counter-tuning behaviors of difference-frequency generation and spontaneous parametric down-conversion. By combining these advances with ultra-narrowband filtering, we achieve a record-high external efficiency of 28.8% and an ultra-low noise of 35 counts per second. This high-performance QFC connecting ultraviolet and telecom bands satisfies the stringent requirements for long-lived remote ion-ion entanglement in scalable quantum networks [W.-Z. Liu et al., Nature (2026)].
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) between the visible and telecom is a key to connect quantum memories in fiber-based quantum networks. Current methods for linking such widely separated frequencies, such as sum/difference frequency generation and four-wave mixing Bragg scattering, are prone to broadband noise generated by the pump laser(s). To address this issue, we propose to use third-order sum/difference frequency generation (TSFG/TDFG) for an upconversion/downconversion QFC interface. In this process, two long wavelength pump photons combine their energy and momentum to mediate frequency conversion across the large spectral gap between the visible and telecom bands, which is particularly beneficial from the noise perspective. We show that waveguide-coupled silicon nitride microring resonators can be designed for efficient QFC between 606 and 1550 nm via a 1990 nm pump through TSFG/TDFG. We simulate the device dispersion and coupling, and from the simulated parameters, estimate that the frequency conversion can be efficient (>80%{\gt}80 \%>80%) at 50 mW pump power. Our results suggest that microresonator TSFG/TDFG is promising for compact, scalable, and low-power QFC across large spectral gaps.
Frequency upconversion for single photons at telecom wavelengths is important to simultaneously meet the different wavelength requirements for long-distance communications and quantum memories in a quantum nodal network. It also enables the detection for the telecom "flying qubit" photons with silicon-based efficient single-photon detectors with low dark count (DC) rates. Here, we demonstrate the frequency upconversion of attenuated single photons, using a low-loss titanium-indiffused periodically poled lithium niobate waveguide, pumped with a readily available erbium-doped fiber amplifier in the L-band. Internal and conversion efficiencies up to 84.4% and 49.9% have been achieved, respectively. The DC rates are suppressed down to 44 kHz at 13.9% end-to-end quantum efficiency (including full conversion and detection), enabled by our long-wavelength pump configuration and narrow 3.5-GHz bandpass filtering.