All-optical quantum coherent control of electron spin in semiconductor QDs

SJ Xu

Timothy M. Sweeney

Takahiro Inagaki, Hideo Kosaka, Yoshiaki Rikitake +3 more

M. V. Gurudev Dutt

Semiconductor quantum dots (QDs) are ideal candidates for quantum information processing, due to their strong resemblance to atomic systems. This paper will show that an optically driven approach is an attractive scheme for quantum computing with QDs. Results will be presented from the experiments with the optical Bloch vector qubit in neutral QDs, demonstrating phase‐locked single qubit rotations and two‐qubit universal control‐NOT logic gates. We will conclude by discussing how the optical approach can be extended to control the electron spin qubit in charged QDs.

Gabriela M. Slavcheva, Ortwin G. Hess

Yuxi Jiang, Amirehsan Alizadehherfati, Christine Falter +6 more

Coherent spin-photon interfaces are essential for scalable quantum networks, but their realization requires optically bright transitions, long-lived spin coherence, and complete coherent control. Donor-bound electron spins in II-VI semiconductors offer an attractive platform for optically active spin qubits because they combine strong donor-bound exciton transitions in a direct-bandgap material with a potentially nuclear-spin-free environment. However, coherent control of an individual optically active donor spin has remained elusive. Here we demonstrate optical initialization, coherent control, and readout of a single donor-bound electron spin in ZnSe. Using spin-selective donor-bound exciton optical transitions, we initialize the electron spin and directly resolve its spin-relaxation dynamics. We achieve coherent spin control with off-resonant picosecond optical pulses, as demonstrated by spin Rabi oscillations and Ramsey interference. We further coherently drive two spin-selective optical transitions and observe high-contrast coherent population trapping, demonstrating the formation of an optically controlled dark state. At higher driving strengths, multiple dark resonances reveal the hyperfine interaction between the electron and the I = 3/2 Cl nucleus. These results establish the first coherent optical control of a single donor electron spin in a II-VI semiconductor and identify isolated optical donors as a promising platform for solid-state optically active qubits.