Charge noise acting on graphene double quantum dots in circuit quantum electrodynamics architecture

We investigate the dephasing mechanisms induced by the charge noise and microwave heating effect acting on a graphene double quantum dot （DQD） capacitively coupled to a microwave resonator. The charge noise is obtained from DC transport current, and its contribution to dephasing is simultaneously determined by the amplitude response of the microwave resonator. A lowfrequency 1/f-type noise is demonstrated to be the dominant factor of the dephasing of graphene DQD. Furthermore, when the applied microwave power is larger than -90 dBm, the dephasing rate of graphene DQD increases rapidly with the increase of microwave power, and fluctuates slightly with the applied microwave power smaller than -90 dBm. Our results can be applied to suppress the impeditive influence on the dephasing of graphene-based devices associated with microwave input in the perspective investigations.

Plasma-Enhanced Atomic Layer Deposition of Amorphous Ga_(2)O_(3) for Solar-Blind Photodetection

Wide-bandgap gallium oxide(Ga_(2)O_(3))is one of the most promising semiconductor materials for solar-blind(200 nm to 280 nm)photodetection.In its amorphous form,amorphous gallium oxide(a-Ga_(2)O_(3))maintains its intrinsic optoelectronic properties while can be prepared at a low growth temperature,thus it is compatible with Si integrated circuits(ICs)technology.Herein,the a-Ga_(2)O_(3) film is directly deposited on pre-fabricated Au interdigital electrodes by plasma enhanced atomic layer deposition(PE-ALD)at a growth temperature of 250°C.The stoichiometric a-Ga_(2)O_(3) thin film with a low defect density is achieved owing to the mild PE-ALD condition.As a result,the fabricated Au/a-Ga_(2)O_(3)/Au photodetector shows a fast time response,high responsivity,and excellent wavelength selectivity for solar-blind photodetection.Furthermore,an ultra-thin MgO layer is deposited by PE-ALD to passivate the Au/a-Ga_(2)O_(3)/Au interface,resulting in the responsivity of 788 A/W(under 254 nm at 10 V),a 250-nm-to-400-nm rejection ratio of 9.2×10^(3),and the rise time and the decay time of 32 ms and 6 ms,respectively.These results demonstrate that the a-Ga_(2)O_(3) film grown by PE-ALD is a promising candidate for high-performance solar-blind photodetection and potentially can be integrated with Si ICs for commercial production.

Quantum dot behavior in transition metal dichalcogenides nanostructures

Recently, transition metal dichalcogenides （TMDCs） semiconductors have been utilized for investi- gating quantum phenomena because of their unique band structures and novel electronic properties. In a quantum dot （QD）, electrons are confined in all lateral dimensions, offering the possibility for detailed investigation and controlled manipulation of individual quantum systems. Beyond the defini- tion of graphene QDs by opening an energy gap in nanoconstrictions, with the presence of a bandgap, gate-defined QDs can be achieved on TMDCs semiconductors. In this paper, we review the confim~ ment and transport of QDs in TMDCs nanostructures. The fabrication techniques for demonstrating two-dimensional （2D） materials nanostructures such as field-effect transistors and QDs, mainly based on e-beam lithography and transfer assembly techniques are discussed. Subsequently, we focus on electron transport through TMDCs nanostructures and QDs. With steady improvement in nanoscale materials characterization and using graphene as a springboard, 2D materials offer a platform that allows creation of heterostructure QDs integrated with a variety of crystals, each of which has entirely unique physical properties.

Effect of dispersion on indistinguishability between single-photon wave-packets

With propagating through a dispersive medium,the temporal–spectral profile of optical pulses should be inevitably modified.Although such dispersion effect has been well studied in classical optics,its effect on a singlephoton wave-packet has not yet been entirely revealed.In this paper,we investigate the effect of dispersion on indistinguishability between single-photon wave-packets through the Hong–Ou–Mandel(HOM)interference.By dispersively manipulating two weak coherent single-photon wave-packets which are prepared by attenuating mode-locked laser pulses before interfering with each other,we observe that the difference of the second-order dispersion between two optical paths of the HOM interferometer can be mapped to the interference curve,indicating that(i)with the same amount of dispersion effect in both paths,the HOM interference curve must be only determined by the intrinsic indistinguishability between the wave-packets,i.e.,dispersion cancellation due to the indistinguishability between Feynman paths;and(ii)unbalanced dispersion effect in two paths cannot be canceled and will broaden the interference curve thus providing a way to measure the second-order dispersion coefficient.Our results suggest a more comprehensive understanding of the single-photon wave-packet and pave ways to explore further applications of the HOM interference.

Visualizing nonlinear resonance in nanomechanical systems via single-electron tunneling

Numerous reports have elucidated the importance of mechanical resonators comprising quantum-dot-embedded carbon nanotubes(CNTs)for studying the effects of single-electron transport.However,there is a need to investigate the single-electron transport that drives a large amplitude into a nonlinear regime.Herein,a CNT hybrid device has been investigated,which comprises a gate-defined quantum dot that is embedded into a mechanical resonator under strong actuation conditions.The Coulomb peak positions synchronously oscillate with the mechanical vibrations,enabling a single-electron Chopper*1 mode.Conversely,the vibration amplitude of the CNT versus its frequency can be directly visualized via detecting the time-averaged single-electron tunneling current.To understand this phenomenon,a general formula is derived for this time-averaged single-electron tunneling current,which agrees well with the experimental results.By using this visualization method,a variety of nonlinear motions of a CNT mechanical oscillator have been directly recorded,such as Duffing nonlinearity,parametric resonance,and double-,fractional-,mixed-frequency excitations.This approach opens up burgeoning opportunities for investigating and understanding the nonlinear motion of a nanomechanical system and its interactions with electron transport in quantum regimes.