Abstract
Quantum photonic circuits with integrated on-demand quantum emitters can act as building blocks for photonic gates and processors with enhanced quantum functionality. To scale up such quantum devices to larger and more powerful systems, eventually reaching the quantum advantage, the scalable integration of many emitters with identical emission wavelengths is of utmost importance. Here, we report on the deterministic integration of self-assembled quantum dots (QDs) in waveguide structures by means of in situ electron beam lithography (EBL). Applying external bias voltages to the p-i-n-doped and electrically contacted quantum circuits allows for spectral fine-tuning of the QDs via the quantum confined Stark effect. We achieve a tuning range of (0.40 ± 0.16) nm, which together with a spectral pre-selection accuracy of (0.2 ± 1.6) nm in the in situ EBL process is on average large enough to tune individual QDs into resonance. Thus, deterministic QD integration with spectral pre-selection in conjunction with Stark tuning of the QD emission wavelength is an attractive combination that has high potential to enable the scalable fabrication of integrated quantum photonic circuits in the future.
Highlights
Waveguides with deterministically integrated emitters of single and indistinguishable photons are key elements of integrated quantum photonic circuits (IQPCs).1–3 In order to be able to implement a powerful optical quantum computer with these non-classical light sources, the photon-coupling efficiency of the emitters to waveguides must be maximized.4 In addition, it must be ensured that all sources emit photons of identical wavelengths in order to enable photon–photon interactions through the Hong–Ou–Mandel (HOM) effect, which is at the heart of, for instance, the boson sampling concept.5,6 Of particular interest are solid-state quantum emitters that provide single photons, in principle, on demand and with a high emission rate
A p-i-n diode sample design was developed, which allows for Stark tuning of quantum dots (QDs)-WGs and is compatible with the in situ electron beam lithography (EBL) process
We found that the emission lines of deterministically integrated QDs shift on average by Δλ = (0.2 ± 1.6) nm when compared to the spectral features during fabrication and for the final device
Summary
Waveguides with deterministically integrated emitters of single and indistinguishable photons are key elements of integrated quantum photonic circuits (IQPCs). In order to be able to implement a powerful optical quantum computer with these non-classical light sources, the photon-coupling efficiency of the emitters to waveguides must be maximized. In addition, it must be ensured that all sources emit photons of identical wavelengths in order to enable photon–photon interactions through the Hong–Ou–Mandel (HOM) effect, which is at the heart of, for instance, the boson sampling concept. Of particular interest are solid-state quantum emitters that provide single photons, in principle, on demand and with a high emission rate. The sample design must meet the following requirements: (a) enable the finetuning of the QD emission wavelength by the QCSE, (b) be compatible with the in situ EBL manufacturing process, (c) ensure high QD-waveguide coupling, and (d) provide strong wave guiding. We would like to note that our waveguide design is not optimized for strong waveguiding
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