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arXiv:1801.03304 · Physical Review Applied

Quantum Frequency Conversion of Single Photons from a Nitrogen-Vacancy Center in Diamond to Telecommunication Wavelengths

A. Dréau, Anna Tcheborateva, Aboubakr El Mahdaoui, Cristian Bonato, Ronald Hanson

Published Jun 19, 2018• 146 citations
arXivHTMLPDF

Abstract

Entanglement-based quantum networks are strongly pursued worldwide, because of their potential impact on secure communication, distributed quantum computing, and timekeeping, for example. Among quantum emitters, the N-$V$ center in diamond is a leading candidate for implementing such networks, but high photon loss at the N-$V$ emission wavelength hinders long-distance entanglement (beyond ~1 km). The authors surmount this hurdle by down-converting single N-$V$ photons to a telecom wavelength, via nonlinear optics plus efficient filtering and excellent control of a lone emitter. This technological achievement is a critical step toward large-scale quantum networks.

DOI
10.1103/physrevapplied.9.064031

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Entanglement-based quantum networks are strongly pursued worldwide, because of their potential impact on secure communication, distributed quantum computing, and timekeeping, for example. Among quantum emitters, the N-VVV center in diamond is a leading candidate for implementing such networks, but high photon loss at the N-VVV emission wavelength hinders long-distance entanglement (beyond ~1 km). The authors surmount this hurdle by down-converting single N-VVV photons to a telecom wavelength, via nonlinear optics plus efficient filtering and excellent control of a lone emitter. This technological achievement is a critical step toward large-scale quantum networks.
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.
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 a string of telecom photons displaying the SnV lifetime, confirming successful conversion. These results represent a critical step towards metropolitan-scale fiber-based quantum networks using SnV centers.
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 networks promise secure communication, distributed sensing and modular quantum computing by interconnecting distant quantum nodes through photonic links. Extending such networks beyond metropolitan distances requires quantum repeaters to overcome the exponential attenuation of photons in optical fiber. Across all architectures, a key requirement is the indistinguishability of single photons, which directly impacts the fidelity of photonic operations based on two-photon interference, such as Bell-state measurements and fusion gates. Here, we demonstrate generation of highly indistinguishable single photons from a coherently excited tin-vacancy center in diamond, achieving raw Hong-Ou-Mandel interference visibilities exceeding 0.95. By separating intrinsic emitter properties from technical imperfections, we show that decoherence plays a negligible role and that the remaining limitations are predominantly technical in nature, arriving at an intrinsic indistinguishability of up to 0.999. We further show that quantum frequency conversion to the telecom C-band preserves the photon indistinguishability. In combination with the long-lived electron and nuclear spin coherence times, these results establish tin-vacancy centers in diamond as a competitive platform for long-distance quantum networks and photonic quantum information processing. We further substantiate this potential through Monte Carlo simulations of a quantum-repeater link, demonstrating that the SnV-center platform surpasses the bound set by direct transmission.
Abstract Solid-state spins such as nitrogen-vacancy (NV) center are promising platforms for large-scale quantum networks. Despite the optical interface of NV center system, however, the significant attenuation of its zero-phonon-line photon in optical fiber prevents the network extended to long distances. Therefore a telecom-wavelength photon interface would be essential to reduce the photon loss in transporting quantum information. Here we propose an efficient scheme for coupling telecom photon to NV center ensembles mediated by rare-earth doped crystal. Specifically, we proposed protocols for high fidelity quantum state transfer and entanglement generation with parameters within reach of current technologies. Such an interface would bring new insights into future implementations of long-range quantum network with NV centers in diamond acting as quantum nodes.
Long-distance quantum communication requires entanglement between distant quantum memories. For this purpose, photon transmission is necessary to connect the distant memories. Here, for the first time, we develop a two-step frequency conversion process (from a visible wavelength to a telecommunication wavelength and back) involving the use of independent two-frequency conversion media where the target quantum memories are nitrogen-vacancy centers in diamonds (with an emission/absorption wavelength of 637.2 nm), and experimentally characterize the performance of this process acting on light from an attenuated CW laser. A total conversion efficiency of approximately 7% is achieved. The noise generated in the frequency conversion processes is measured, and the signal-to-noise ratio is estimated for a single photon signal emitted by a nitrogen-vacancy (NV) center. The developed frequency conversion system has future applications via transmission through a long optical fiber channel at a telecommunication wavelength for a quantum repeater network.