Quantum dots are nanoscale semiconductor structures that confine electrons in three dimensions. They exhibit discrete energy levels due to quantum confinement, like atoms. In the context of spin qubits, the quantum states of these confined electrons' spins (spin-up and spin-down) serve as the basis for quantum information processing [1]. The goal of controlled excitation of quantum dot spins is to achieve coherent manipulation and readout of quantum information encoded in the spin states. By confining excitation to the chip, we develop compact, scalable platforms exploiting quantum dots' unique properties for advanced technological applications. This excitation is typically achieved using optical modes confined within waveguides that are fabricated on the chip itself (Figure 1). The term "on-chip" indicates that the excitation process occurs within the same physical substrate or device where the quantum emitter is located [2]. This integration is crucial for practical devices, particularly in quantum information processing and photonics. Compared to off-chip methods, on-chip excitation enhances emitter efficiency by minimizing losses related to external coupling. Exciting quantum emitters on-chip enhances operational control and interaction with other device components, crucial for precise quantum operations. This contributes to miniaturizing quantum technologies, reducing device size for portability. On-chip excitation is vital for spin-based quantum computing architectures, impacting spintronics and quantum communication.
Figure 1: On-chip excitation of a chirally-coupled quntum dot in a symmetry-broken photonic crystal waveguide. (a) Schematic of the device layout. (b) Remote excitation of quantum dot spins using right (red) and left (blue) outcouplers positioned at the waveguide end.
References
[1] H. Siampour et al., "Observation of large spontaneous emission rate enhancement of quantum dots in a broken-symmetry slow-light waveguide," npj Quantum Information, vol. 9, no. 1, p. 15, 2023/02/22 2023, doi: 10.1038/s41534-023-00686-9.
[2] H. Siampour, S. Kumar, V. A. Davydov, L. F. Kulikova, V. N. Agafonov, and S. I. Bozhevolnyi, "On-chip excitation of single germanium vacancies in nanodiamonds embedded in plasmonic waveguides," Light: Science & Applications, vol. 7, no. 1, p. 61, 2018/09/12 2018, doi: 10.1038/s41377-018-0062-5