Free lunch at 12:00

The spin of a single electron confined in a quantum dot is a promising matter qubit for quantum information processing. This spin system possesses microsecond coherence time and allows picosecond timescale control using optical pulses. It is also embedded in a host semiconductor substrate that can be directly patterned to form compact integrated nanophotonic devices for photonic interfaces.

In this talk, I will discuss our efforts to develop nanophotonic quantum interface for a single quantum dot spin qubit by strongly coupling the quantum dot to a photonic crystal cavity. I will firstly present a quantum switch between a quantum dot spin and a photon [1]. This switch realizes a transistor operating at the fundamental quantum limit, where in picoseconds timescales a single photon flips the orientation of a spin and the spin flips the polarization of the photon. This device could enable spin-photon entanglement [2], and thus plays an important role in integrated quantum networks involving multiple solid-state spin qubits interconnected by flying photons. Next I will show cavity enhanced optical readout of a quantum dot spin [3]. This approach utilizes the spin-dependent cavity reflectivity to determine the spin state, and is particularly suitable for qubits such as quantum dot spins that do not possess a good cycling transition for resonance fluorescence detection. I will conclude with a discussion of the future prospects of this technology for developing chip-integrated quantum information systems.

[1] S. Sun et. al., Nature Nanotechnology advanced online publication (2016), doi:10.1038/nnano.2015.334.

[2] S. Sun and E. Waks, Physical Review A 90, 042322 (2014).

[3] S. Sun and E. Waks, arXiv:1602.04367 (2016).