On-chip quantum memories based on erbium dopants in silicon waveguides

• Applicant: Professor Dr. Andreas Reiserer
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452035973

The realization of global quantum networks via quantum repeaters is one of the most intensely pursued topics in current quantum science. It would not only facilitate novel fundamental and precision tests of quantum theory, but also enable numerous applications in quantum information processing.To implement a large quantum network, quantum memories that fulfil stringent criteria are required. First, they need to offer sufficient storage time, on the order of 1 s. Second, they have to facilitate storage and on-demand retrieval of qubits with high efficiency and fidelity. Third, they must act as a source (or be compatible with sources) of single photons in the low-loss telecom bands. Finally, they should provide a simple strategy for efficient multiplexing, which typically requires multimode capacity, low-cost material, robustness and scalable fabrication techniques.In spite of numerous efforts in different physical platforms, the realization of such quantum memory is still an outstanding challenge. In particular, the latter two criteria have proven difficult in previous experiments. Therefore, a new technology that overcomes the bottlenecks of existing physical systems seems mandatory. To this end, we are planning to investigate erbium dopants in nanophotonic waveguides made of crystalline silicon.In general, memories based on dopants are particularly promising as they offer the longest coherence times of any quantum system – up to six hours – and they provide a clear path towards scalability. Among all dopants studied to date, erbium stands out because its emission wavelength falls within the main wavelength band of optical telecommunication between 1530 nm and 1565 nm. This has two advantages: first, the transparency of silicon in this wavelength regime ensures compatibility with the mature platform of silicon nano-photonics, providing a clear path for multiplexing. Second, the minimal loss of optical fibers at this wavelength is a key requirement for quantum networks that span global distances.Our new experimental platform builds on standard processes of the semiconductor industry, which dramatically reduces the experimental overhead compared to all other platforms under investigation. By harnessing the potential of silicon nanofabrication towards the realization of integrated nanophotonic quantum memories, we thus expect to establish a critical capability for provably-secure communication and for network-based quantum information processing.

• DFG Programme: Research Grants