We investigate the crossover between weak localization and weak antilocalization in InAs nanowires of different diameters ͑75 nm-140 nm-217 nm͒. For a magnetic field applied perpendicularly to the nanowire axis, we extract the spin orbit and coherence lengths using a quasi-one-dimensional model of the conductance. We find a spin-orbit length inversely proportional to the width of the nanowire. When a parallel magnetic field is applied, we observe that the weak-antilocalization contribution is less affected by the magnetic field than in the perpendicular case.

We study a graphene double quantum dot in different coupling regimes. Despite the strong capacitive coupling between the dots, the tunnel coupling is below the experimental resolution. We observe additional structures inside the finite-bias triangles, part of which can be attributed to electronic excited dot states, while others are probably due to modulations of the transmission of the tunnel barriers connecting the system to source and drain leads.

The coupling between a two-level system and its environment leads to decoherence. Within the context of coherent manipulation of electronic or quasiparticle states in nanostructures, it is crucial to understand the sources of decoherence. Here, we study the effect of electronphonon coupling in a graphene and an InAs nanowire double quantum dot. Our measurements reveal oscillations of the double quantum dot current periodic in energy detuning between the two levels. These periodic peaks are more pronounced in the nanowire than in graphene, and disappear when the temperature is increased. We attribute the oscillations to an interference effect between two alternative inelastic decay paths involving acoustic phonons present in these materials. This interpretation predicts the oscillations to wash out when temperature is increased, as observed experimentally.Coherent spin manipulation has already been accomplished in AlGaAs/GaAs double quantum dots (DQDs) 1, 2 and, more recently, also in InAs nanowires (NWs) 3 . While the coherence times are usually limited by random nuclear fields 4 , also electron-phonon coupling can be a source of decoherence 5 . InAs nanowires (NW) and graphene are two alternative and promising materials for achieving coherent spin manipulation. In InAs NW DQDs, spin-orbit interactions (SOI) are very strong and enable a more efficient electron spin resonance driven by SOI compared to AlGaAs/GaAs DQDs 3 . In graphene, it is expected that hyperfine coupling as a source of decoherence is very weak compared to AlGaAs/GaAs. While electron-phonon interaction effects have been observed in carbon nanotube 6, 7 , AlGaAs/GaAs 8 , or silicon quantum dots (QDs) 9 and in AlGaAs/GaAs DQDs 10, 11 , only little is known about electron-phonon interaction in graphene and InAs nanowires.Almost 60 years ago, Dicke predicted superradiant and subradiant spontaneous emission 12 , which was observed 40 years later with two trapped ions 13 . In this experiment, the spontaneous emission rate Γ(R) of a two-ion crystal excited by a short laser pulse was studied as a function of the ion-ion separation R. Superradiant (subradiant) spontaneous emission was observed with Γ(R) > Γ 0 (Γ(R) < Γ 0 ), where Γ 0 is the emission rate of a single ion. In analogy to the Dicke subradiance phenomenon, Brandes et al. 14 later proposed an interference effect due to electronphonon interactions in a solid-state two-level system (DQD). Our experimental observations are interpreted in this framework.

In graphene-based electronic devices like in transistors, the field effect applied thanks to a gate electrode allows tuning the charge density in the graphene layer and passing continuously from the electron to the hole doped regime across the Dirac point. Homogeneous doping is crucial to understand electrical measurements and for the operation of future graphene-based electronic devices. However, recently theoretical and experimental studies highlighted the role of the electrostatic edge due to fringing electrostatic field lines at the graphene edges [P. Silvestrov and K. Efetov,

Low-temperature transport experiments on a p-type GaAs quantum dot capacitively coupled to a quantum point contact are presented. The time-averaged as well as time-resolved detection of charging events of the dot are demonstrated and they are used to extract the tunnelling rates into and out of the quantum dot. The extracted rates exhibit a super-linear enhancement with the bias applied across the dot which is interpreted in terms of a dense spectrum of excited states contributing to the transport, characteristic for heavy hole systems. The full counting statistics of charge transfer events and the effect of back action is studied. The normal cumulants as well as the recently proposed factorial cumulants are calculated and discussed in view of their importance for interacting systems.

A gate-defined quantum dot in an InAs nanowire is fabricated on top of a quantum point contact realized in a two-dimensional electron gas. The strong coupling between these two quantum devices is used to perform time-averaged as well as time-resolved charge detection experiments for electron flow through the quantum dot. We demonstrate that the Fano factor describing shot noise or timecorrelations in single-electron transport depends in the theoretically expected way on the asymmetry of the tunneling barriers even in a regime where the thermal energy kBT is comparable to the singleparticle level spacing in the dot.

We report on correlated real-time detection of individual electrons in an InAs nanowire double quantum dot. Two self-aligned quantum point contacts in an underlying two-dimensional electron gas material serve as highly sensitive charge detectors for the double quantum dot. Tunnel processes of individual electrons and all tunnel rates are determined by simultaneous measurements of the correlated signals of the quantum point contacts.

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