A Telecom-Compatible Quantum Memory in the Solid-State: Single Erbium Ions Coupled to Silicon Nanophotonic Circuits

Gaia Da Prato

Ioana Craiciu, Mi Lei, Jake Rochman +5 more

Yu-Yang An, Qian He, Wenyi Xue +5 more

To realize a quantum internet, the distribution of quantum states via quantum teleportation with quantum memories is a key ingredient. Being compatible with existing fiber networks, entangled photons and quantum memories at telecom wavelength are of central interest for such a scalable quantum network. Here, we demonstrate quantum teleportation from a telecom-wavelength photonic qubit to a solid-state quantum memory based on erbium-ion ensembles, which have a native optical transition at 1.5 μm telecom C band. To accomplish this, we use chip-scale silicon nitride microresonators to generate entangled photons with narrow linewidth, compatible with the quantum memory. We confirm the quality of the quantum teleportation procedure using quantum state and process tomography techniques, in which both the quantum state and process fidelities exceeds the classical limit. These results pave the way for the realization of scalable quantum networks based on solid-state devices.

Alan Dibos, Michael T. Solomon, Sean E. Sullivan +9 more

High Resolution Image Download MS PowerPoint Slide Isolated solid-state atomic defects with telecom optical transitions are ideal quantum photon emitters and spin qubits for applications in long-distance quantum communication networks. Prototypical telecom defects, such as erbium, suffer from poor photon emission rates, requiring photonic enhancement using resonant optical cavities. Moreover, many of the traditional hosts for erbium ions are not amenable to direct incorporation with existing integrated photonics platforms, limiting scalable fabrication of qubit-based devices. Here, we present a scalable approach toward CMOS-compatible telecom qubits by using erbium-doped titanium dioxide thin films grown atop silicon-on-insulator substrates. From this heterostructure, we have fabricated one-dimensional photonic crystal cavities demonstrating quality factors in excess of 5 × 10 4 and corresponding Purcell-enhanced optical emission rates of the erbium ensembles in excess of 200. This easily fabricated materials platform represents an important step toward realizing telecom quantum memories in a scalable qubit architecture compatible with mature silicon technologies.

Alex Kaloyeros, Natasha Tabassum, Spyros Gallis

Achieving long lived (μs-scale) quantum coherence at room temperature in the telecom C band remains a central unsolved challenge for solid state quantum platforms, with coherence at this timescale previously demonstrated only under vacuum cryogenic conditions at temperatures over 600 times lower. To this end, we introduce a CMOS-compatible nanoengineering approach that deterministically controls the number of Er ions within a nanoscale volume and their electromagnetic environment using sub 5 nm silicon based hollow nanopillars, which achieves the first deterministic spatial isolation of single erbium ions. This nanostructure-enabled isolation suppresses ion-ion interactions and local electromagnetic field noise, enabling single-erbium-ion operation under ambient conditions. The resulting individually addressable single-ion devices exhibit record room temperature optical coherence times of T2* = ~32 μs in the telecom C-band (limited by the coherence of the laser) and extending to > 100 μs based on photon echo measurements. We further present the first demonstration of background free, upconversion enabled single photon emission from multilevel erbium qudits, providing high contrast coherent optical readout. Beyond these performance gains, our work, through sub-5-nm nanoscale engineering, establishes isolated single-ion environments as a viable route to room-temperature operation for solid-state quantum systems. This approach has the potential to address the long-standing barrier of room-temperature decoherence and open a manufacturable, telecom-compatible pathway toward scalable quantum networks, distributed sensing, and cryogenic-free quantum photonic integrated circuits.

Andrei Faraon