Controlling couplings between quantum dots in a quantum dot array

Recent demonstrations using electron spins stored in quantum dot array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is, therefore, aiming at the precise control of the quantum dot parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling, and sub-Hz isolation between adjacent dots. We use this development to isolate a subpart of the array in a metastable configuration while performing charge displacement and readout in the rest of the system. The degree of control over tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation, and readout including this capability.Recent demonstrations using electron spins stored in quantum dot array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is, therefore, aiming at the precise control of the quantum dot parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling, and sub-Hz isolation between adjacent dots. We use this development to isolate a subpart of the array in a metastable configuration while performing charge displacement and readout in the rest of the system. The degree of control over tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation, and readout including this capability.

arXiv:2207.09235Applied Physics LettersAug 22, 20227 citations

Site-controlled quantum dot arrays edge-coupled to integrated silicon nitride waveguides and devices

John O'Hara, Nicola Maraviglia, Mack Johnson +7 more

The scalability of quantum photonic integrated circuits opens the path towards large-scale quantum computing and communication. To date, this scalability has been limited by the stochastic nature of the quantum light sources. Moreover, hybrid integration of different platforms will likely be necessary to combine state-of-the-art devices into a functioning architecture. Here, we demonstrate the active alignment and edge-coupling of arrays of ten site-controlled gallium arsenide quantum dots to an array of ten silicon nitride single-mode waveguides, at cryogenic temperatures. The coupling is facilitated by the fabrication of nanopillars, deterministically self-aligned around each quantum dot, leading to a high-yield and regular array of single-photon sources. An on-chip beamsplitter verifies the triggered emission of single photons into the silicon nitride chip. The low inhomogeneous broadening of the ensemble enables us to observe the spectral overlap of adjacent site-controlled emitters. Across the array of waveguides, the signal collected from each coupled quantum dot is consistently and reproducibly 0.17 relative to the free-space collection from the very same single-photon source. Comparing measurement with waveguide simulations, we infer that absolute coupling efficiencies of $\approx 5 \%$ are currently obtained between our quantum dots and the waveguides.The scalability of quantum photonic integrated circuits opens the path towards large-scale quantum computing and communication. To date, this scalability has been limited by the stochastic nature of the quantum light sources. Moreover, hybrid integration of different platforms will likely be necessary to combine state-of-the-art devices into a functioning architecture. Here, we demonstrate the active alignment and edge-coupling of arrays of ten site-controlled gallium arsenide quantum dots to an array of ten silicon nitride single-mode waveguides, at cryogenic temperatures. The coupling is facilitated by the fabrication of nanopillars, deterministically self-aligned around each quantum dot, leading to a high-yield and regular array of single-photon sources. An on-chip beamsplitter verifies the triggered emission of single photons into the silicon nitride chip. The low inhomogeneous broadening of the ensemble enables us to observe the spectral overlap of adjacent site-controlled emitters. Across the array of waveguides, the signal collected from each coupled quantum dot is consistently and reproducibly 0.17 relative to the free-space collection from the very same single-photon source. Comparing measurement with waveguide simulations, we infer that absolute coupling efficiencies of $\approx 5 \%$ are currently obtained between our quantum dots and the waveguides.

physics.opticsCross-listedarXiv:2512.07535Dec 9, 2025

\approx 5 \%

are currently obtained between our quantum dots and the waveguides.