Deterministic assembly of a spin-photon interface based on a semiconductor quantum dot

Y. L. Delley

A. Oiwa

Jyun-Jie Jiang, Pericles Philippopoulos, Félix Beaudoin +1 more

Spin-photon interfaces are essential for communications between distant spin qubits in quantum technologies, but the interband optical excitation can also damp electrically driven hole-spin Rabi oscillations in semiconductor self-assembled quantum dots (SAQDs). We report a device-level modeling workflow that integrates realistic SAQD geometry and multiband electronic-structure analysis with models of electrically driven spin control, interband optical transitions, and open-system dynamics. This workflow enables device-level estimation of Rabi-oscillation damping arising from repeated interband absorption-emission cycles. As an example, for a gated GaAs SAQD subjected to a uniform magnetic field $B_0$ along the growth direction of the SAQD, we predict the Rabi frequency of the hole spin qubit and its damping under external illumination. At $B_0=2$ T, the calculations yield a hole-spin Rabi frequency of 37.3 MHz. When the electrically driven SAQD is illuminated by a broadband LED centered at a wavelength of 790 nm, increasing the optical power from 0.3 to 1.5 mW shortens the Rabi-oscillation decay time from 90.3 to 17.5 ns. Increasing the SAQD height reduces the electron-hole overlap and thus the emission rate, but the resulting redshift moves the interband transitions into stronger spectral overlap with the LED spectrum, thereby increasing the rate of repeated absorption-emission cycles and enhancing photon-induced Rabi-oscillation damping. The results show that geometry, spin-control conditions, and illumination spectrum should be co-optimized in semiconductor spin-photon devices.

Johannes M. Michl, Reza Hekmati, Mohamed Helal +9 more

Matter qubits that maintain coherence over extended timescales are essential for many pursued applications in quantum communication and quantum computing. Significant progress has already been made on extending coherence times of spins in semiconductor quantum dots while interfacing them with photons in the near-infrared wavelength range. However, similar results for quantum dots emitting at the telecom range, crucial for many applications, have so far lagged behind. Here, we report on InAs/InAlGaAs quantum dots integrated in a deterministically placed circular Bragg grating emitting at $1.55\,μ\mathrm{m}$. We quantify the g-factors of electrons and holes from polarization-resolved measurements of a positive trion in an in-plane magnetic field and study the dynamics of the ground-state hole spin qubit. We then herald the hole spin in a pulsed two-photon correlation measurement and determine its inhomogeneous dephasing time to $T_{2}^{*}=(15.9 \pm 1.7)$ ns.

Ravitej Uppu, Leonardo Midolo, Xiaoyan Zhou +2 more

Tobias M. Krieger, Michele B. Rota, Julia Freund +4 more

Limited spatial overlap of self-assembled semiconductor quantum dots with photonic structures hinders the scalability of entangled photon sources. Here we present a marker-based cryogenic imaging system enabling strain-tunable and cavity-enhanced quantum dots emitting highly-entangled photons.