All-electrical measurement of the relaxation time of a two-electron spin-triplet state in InAs quantum dots

Many-particle spin states in self-assembled quantum dots (QDs) could serve as qubits in quantum information processing devices. However, in optical experiments always the excitonic states are measured, hence, electrical preparation and detection of pure excited many-particle states without electron-hole interaction are still missing. We demonstrate an all-electrical spectroscopy technique on an ensemble of InAs QDs. It allows us to prepare and detect the pure many-particle electron states with their spin-singlet and -triplet configurations, using a time-resolved measurement detection scheme via a 2DEG. This all-electrical measurement scheme enables us to determine the electron spin-relaxation time without an applied magnetic field and without optical excitation to 5 ms at 4 K. The spin relaxation time is independent on the applied magnetic field (up to 2 T) and slightly decreases down to 3 ms at 50 K.