arXiv subjects

Guo-Ping Guo

Publications and source records attributed to Guo-Ping Guo.

At least 181 records · Page 10Linked to original sources

arXiv2011

Exciton-Plasmon-Photon Conversion in silver nanowire: polarization dependence

Polarization dependence of the exciton-plasmon-photon conversion in silver nanowire-quantum dots structure was investigated using a scanning confocal microscope system. We found that the fluorescence enhancement of the CdSe nanocrystals was correlated with the angle between the excitation light polarization and the silver nanowire direction. The polarization of the emission was also related with the nanowire direction. It was in majority in the direction parallel with nanowire.

physics.optics↗

arXiv2011

Gates controlled parallel-coupled double quantum dot on both single layer and bilayer graphene

Here we report the fabrication and quantum transport measurements of gates controlled parallel-coupled double quantum dot on both bilayer and single layer graphene. It is shown that the interdot coupling strength of the parallel double dots can be effectively tuned from weak to strong regime by both the in-plane plunger gates and back gate. All the relevant energy scales and parameters of the graphene parallel-coupled double dot can be extracted from the honeycomb charge stability diagrams revealed through the transport measurements.

quant-ph↗

arXiv2010

Tomography of the two-electron spin qubits in semiconductors

We propose an approach to reconstruct two-electron spin qubit states in semiconductor quantum dots by employing tomographic techniques. This procedure exploits the combination of fast gate operations on electron spins trapped in dots and dynamical nuclear polarization of the underlying Ga and As nuclei. The presented method can be an important tool in solid state quantum computation for complete characterization of qubit states and theirs correlations.

quant-ph↗

arXiv2010

A Graphene Quantum Dot with a Single Electron Transistor as Integrated Charge Sensor

We have developed an etching process to fabricate a quantum dot and a nearby single electron transistor as a charge detector in a single layer graphene. The high charge sensitivity of the detector is used to probe Coulomb diamonds as well as excited spectrum in the dot, even in the regime where the current through the quantum dot is too small to be measured by conventional transport means. The graphene based quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit in a nuclear-spin-free quantum world.

cond-mat.mes-hall↗

arXiv2010

Strong and Tunable Spin-Orbit Coupling of One-Dimensional Holes in Ge/Si Core/Shell Nanowires

We investigate the low-temperature magneto-transport properties of individual Ge/Si core/shell nanowires. Negative magneto-conductance was observed, which is a signature of one-dimensional weak antilocalization of holes in the presence of strong spin-orbit coupling. The temperature and back gate dependences of phase coherence length, spin-orbit relaxation time, and background conductance were studied. Specifically, we show the spin-orbit coupling strength can be modulated by more than five folds with an external electric field. These results suggest the Ge/Si nanowire system possesses strong and tunable spin-orbit interactions and may serve as a candidate for spintronics applications.

cond-mat.mes-hall↗

arXiv2010

Andreev reflection enhanced single hole tunneling in Ge/Si core/shell nanowire quantum dot

We experimentally study the electrical transport properties of Ge/Si core/shell nanowire device with two superconducting leads in the Coulomb blockade regime. Anomalous zero field magnetoconductance peaks are observed for the first time at the gate voltages where Coulomb blockade oscillation peaks present. Many evidences indicate this feature is due to Andreev reflection enhanced phase coherent single hole tunneling through the quantum dot, which can be suppressed by an external magnetic field without destroying the superconducting states in the electrodes.

cond-mat.mes-hall↗

arXiv2010

Quantum Bus of Metal Nanowire with Surface Plasmon Polaritons

We develop an architecture for distributed quantum computation using quantum bus of plasmonic circuits and spin qubits in self-assembled quantum dots. Deterministic quantum gates between two distant spin qubits can be reached by using an adiabatic approach in which quantum dots couple with highly detuned plasmon modes in a metallic nanowire. Plasmonic quantum bus offers a robust and scalable platform for quantum optics experiments and the development of on-chip quantum networks composed of various quantum nodes, such as quantum dots, molecules and nanoparticles.

quant-ph↗

arXiv2009

Coulomb blockade in graphene quantum dots

We study the conductance spectrum of graphene quantum dots, both single and multiple cases. The single electron tunneling phenomenon is investigated and the periodicity, amplitude and line shape of the Coulomb blockade oscillations at low temperatures are obtained. Further, we discuss the transport behavior when multiple dots are assembled in array and find a phase transition of conductance spectra from individual Coulomb blockade to collective Coulomb blockade.

cond-mat.mes-hall↗

arXiv2009

Transmission of doughnut light through a bull's eye structure

We experimentally investigate the extraordinary optical transmission of doughnut light through a bull's eye structure. Since the intensity is vanished in the center of the beam, almost all the energy reaches the circular corrugations (not on the hole), excite surface plasmons which propagate through the hole and reradiate photons. The transmitted energy is about 57 times of the input energy on the hole area. It is also interesting that the transmitted light has a similar spatial shape with the input light although the diameter of the hole is much smaller than the wavelength of light.

physics.optics↗

arXiv2009

Substrate Modulated Graphene Quantum Dot

We propose a new method to use gapped graphene as barrier to confine electrons in gapless graphene and form a good quantum dot, which can be realized on an oxygen-terminated $SiO_{2}$ substrate partly H-passivated. In particular, we use ferromagnetic insulators deposited on top of barrier which give rise to a spin related energy spectrum and transport properties. Compared to the complexity of etched quantum dots in graphene, the setup suggested here is a promising candidate for practical applications.

cond-mat.mes-hall↗

arXiv2009

Coupling of higher-mode-light into a single sliver nanowire

Coupling of higher-order-mode light into a single sliver nanowire and the degree of the coupling can be controlled by adjusting the light polarization, showing that nanowire waveguide has no request on the spatial mode of the input light. Photons with different orbital angular momentums (OAM) are used to excite surface plasmons of silver nanowires. The experiment indicates the propagating modes of surface plasmons in nanowires were not the OAM eignenstates.

physics.optics↗

arXiv2009

Coupling of light from an optical fiber taper into silver nanowires

We report the coupling of photons from an optical fiber taper to surface plasmon modes of silver nanowires. The launch of propagating plasmons can be realized not only at ends of the nanowires, but also at the midsection. The degree of the coupling can be controlled by adjusting the light polarization. In addition, we present the coupling of light into multiple nanowires from a single optical fiber taper simultaneously. Our demonstration offers a novel method for optimizing plasmon coupling into nanoscale metallic waveguides and promotes the realization of highly integrated plasmonic devices.

physics.optics↗

arXiv2009

Generation of quantum-dot cluster states with superconducting transmission line resonator

We propose an efficient method to generate cluster states in spatially separated double quantum dots with a superconducting transmission line resonator (TLR). When the detuning between the double-dot qubits transition frequency and the frequency of the full wave mode in the TLR satisfies some conditions, an Ising-like operator between arbitrary two separated qubits can be achieved. Even including the main noise sources, it's shown that the high fidelity cluster states could be generated in this solid system in just one step.

quant-ph↗

arXiv2009

Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dot

We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact (QPC) as a measurement device. We obtain that the QPC measurement induced decoherence is in time scales of microsecond. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with quantum Zeno effect.

quant-ph↗

arXiv2008

Quantum computation with graphene nanoribbon

We propose a scalable scheme to implement quantum computation in graphene nanoribbon. It is shown that electron or hole can be naturally localized in each zigzag region for a graphene nanoribbon with a sequence of Z-shaped structure without exploiting any confined gate. An one-dimensional graphene quantum dots chain is formed in such graphene nanoribbon, where electron or hole spin can be encoded as qubits. The coupling interaction between neighboring graphene quantum dots is found to be always-on Heisenberg type. Applying the bang-bang control strategy and decoherence free subspaces encoding method, universal quantum computation is argued to be realizable with the present techniques.

quant-ph↗

arXiv2008

Numerical Studies of Quantum Hall Ferromagnetism in Two-Subband Systems

We carry out a numerical study of the quantum Hall ferromagnetism in a two-subband system using a set of experimental parameters in a recently experiment [X. C. Zhang, I. Martin, and H. W. Jiang, Phys. Rev. B \textbf{74}, 073301 (2006)]. Employing the self-consistence local density approximation for growth direction wave function and the Hartree-Fock theory for the pseudospin anisotropy energy, we are able to account for the easy-axis and easy-plane quantum Hall ferromagnetism observed at total filling factor $ν= 3$ and $ν= 4$, respectively. Our study provides some insight of how the anisotropy energy, which highly depends upon the distribution of growth direction wave functions, determines the symmetry of the quantum Hall ferromagnets.

cond-mat.mes-hall↗

arXiv2008

Removal of surface plasmon polariton eigenmodes degeneracy

The effect of the tilt angle of metal film on the transmissivity of subwavelength holes in optically thick metal film is investigated. The transmission efficiency is found can be highly dependent on the tilt angle. It is also found that when the input photons are polarized not along the eigenmode directions of surface plasmon polariton, a birefringent phenomenon is observed when the array with periodic of subwavelength holes is tilted. Linear polarization states can be changed to elliptical polarization states and a phase can be added between two eigenmodes. The phase is changed with the tilt angle. A model based on surface plasmon polariton eigenmodes degeneracy is presented to explain these experimental results.

physics.optics↗

arXiv2008

Polarization properties of subwavelength hole arrays consisting of rectangular holes

Influence of hole shape on extraordinary optical transmission was investigated using hole arrays consisting of rectangular holes with different aspect ratio. It was found that the transmission could be tuned continuously by rotating the hole array. Further more, a phase was generated in this process, and linear polarization states could be changed to elliptical polarization states. This phase was correlated with the aspect ratio of the holes. An intuitional model was presented to explain these results.

physics.optics↗