Toward Practical Quantum Computing: Old Principles and New Challenges
Recently, most of the components needed for quantum information processing have been demonstrated in proof of principle experiments. Practical quantum computing adds a long list of additional requirements to the hardware, and in many cases the technology behind a proof of concept experiment cannot satisfy all of them. That calls for new, at times fundamentally new, approaches. In my talk I will cover two projects aimed at bridging the gap between earlier experiments and needs of a practical quantum computer.
- Solid-state quantum memory: Robust quantum memories to connect photonic and matter-based qubits are important for scalable quantum information protocols. Here we report our progress on developing a DLCZ-compatible memory in a solid state Pr+3:YSiO5, a rare-earth doped crystal. A solid state quantum memory would offer a low experimental overhead and long coherence times, compared with the demonstrated systems. We demonstrate recording, storage and retrieval of spin waves - a necessary preliminary step in development of such memory. We introduce a simple model that gives an upper bound of cross correlations, and demonstrate that our system performs close to its theoretical limit.
- Hybrid Quantum Interfaces: In building "quantum buses", that help exchange quantum information between the blocks of a quantum computer, it is essential to generate identical quantum states from dissimilar systems. We show that single photons created in a fundamentally different process - parametric down-conversion in a nonlinear crystal - can be manipulated to be indistinguishable from those from quantum dots.