We investigate ground and excited state transport through small (d≈70  nm) graphene quantum dots. The successive spin filling of orbital states is detected by measuring the difference between ground-state energies as a function of a magnetic field. For a magnetic field in-plane of the quantum dot the Zeeman splitting of spin states is measured. The results are compatible with a g factor of 2, a...

Wilson’s Numerical Renormalization Group (NRG) is so far the only nonperturbative technique that can reliably access low–energy properties of quantum impurity systems. We present a recent extension of the method, the DM–NRG, which yields highly accurate results for dynamical quantities at arbitrary frequencies and temperatures. As an application, we determine the spectrum of a quantum dot in an...

Silicon-quantum-dot qubits must contend with low-lying valley excited states that are sensitive functions of the quantum-well heterostructure and disorder; quantifying maximizing energies these critical to improving device performance. We describe a spectroscopic method for probing in isolated $\mathrm{Si}$/$\mathrm{Si}$-$\mathrm{Ge}$ double quantum dots using standard baseband pulsing techniqu...

A highly sensitive charge detector is realized for a quantum dot in an InAs nanowire. We have developed a self-aligned etching process to fabricate in a single step a quantum point contact in a two-dimensional electron gas and a quantum dot in an InAs nanowire. The quantum dot is strongly coupled to the underlying point contact that is used as a charge detector. The addition of one electron to ...

We report on the realization of few-electron double quantum dots defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced ...

Open quantum dots provide a window into the connection between quantum and classical physics, particularly through the decoherence theory, in which an important set of quantum states are not “washed out” through interaction with the environment—the pointer states provide connection to trapped classical orbits which remain stable in the dots. Graphene is a recently discovered material with highl...

Using far-field optical lithography, a single quantum dot is positioned within a pillar microcavity with a 50 nm accuracy. The lithography is performed in situ at 10 K while measuring the quantum dot emission. Deterministic spectral and spatial matching of the cavity-dot system is achieved in a single step process and evidenced by the observation of strong Purcell effect. Deterministic coupling...