Single-electron charge sensing in self-assembled quantum dots

Abstract

Measuring single-electron charge is one of the most fundamental quantum technologies. Charge sensing, which is an ingredient for the measurement of single spins or single photons, has been already developed for semiconductor gate-defined quantum dots, leading to intensive studies on the physics and the applications of single-electron charge, single-electron spin and photon–electron quantum interface. However, the technology has not yet been realized for self-assembled quantum dots despite their fascinating transport phenomena and outstanding optical functionalities. In this paper, we report charge sensing experiments in self-assembled quantum dots. We choose two adjacent dots, and fabricate source and drain electrodes on each dot, in which either dot works as a charge sensor for the other target dot. The sensor dot current significantly changes when the number of electrons in the target dot changes by one, demonstrating single-electron charge sensing. We have also demonstrated real-time detection of single-electron tunnelling events. This charge sensing technique will be an important step towards combining efficient electrical readout of single-electron with intriguing quantum transport physics or advanced optical and photonic technologies developed for self-assembled quantum dots.

Single-charge occupation in ambipolar quantum dots

“…In the left panel of Fig. 2 Previous works have demonstrated simultaneous charge sensing in devices comprising two closely-placed electron QDs [34,35]. In the following we investigate ambipolar simultaneous charge sensing.…”

Ambipolar charge sensing of few-charge quantum dots

“…Previous works have demonstrated simultaneous charge sensing in devices comprising two closely placed electron QDs [37,38]. In the following we investigate ambipolar simultaneous charge sensing.…”

Dynamic generation of GHZ states with coupled charge qubits

“…Quantum Dots (QDs) have been defined as artificial atoms, once the spatial confinement favors the formation of a discrete spectrum of electronic levels [11]. From all the possibilities of encoding a qubit, as in the excitonic states [12][13][14] and the electronic spin [15,16], the interest on the physics of charged quantum dots has been increasing, once they are scalable systems where initialization and readout are possible through a process involving detection even of a single electron [17,18]. In this physical system, the qubits are defined based on the property of electronic tunneling [7,19], with the singlequbit operations being controlled by external gate voltages [7,19].…”