Two‐dimensional interacting electron systems become strongly correlated if the electrons are subject to a perpendicular high magnetic field. After introducing the physics of the quantum Hall regime the incompressible many‐particle ground state and its excitations are studied in detail at fractional filling factors for spin‐polarized electrons. The spin degree of freedom whose importance was shown in recent experiments is considered by studying the thermodynamics at filling factor one and near one. 相似文献
In recent years laser light has been used to control the motion of electron waves. Electrons can now be diffracted by standing waves of light. Laser light in the vicinity of nanostructures is used to affect free electrons, for example, femto‐second and atto‐second laser‐induced electrons are emitted from nanotips delivering coherent fast electron sources. Optical control of dispersion of the emitted electron waves, and optically controlled femto‐second switches for ultrafast electron detection are proposed. The first steps towards electron accelerators and matter optics on‐a‐chip are now being taken. New research fields are driven by these new technologies. One example is the optical generation of electron pulses on‐demand and quantum degenerate pulses. Another is the emerging development of interaction free electron microscopy. This review will focus on the field of free electron quantum optics with technologies at the interplay of lasers, electron matter waves, and nanostructures. Questions that motivate their development will also be addressed.
Herein, an analysis of interference effects as a result of the electron evolution within a coherent transport medium is presented, offering a double‐dopant Coulomb potential structure. Injection of coherent electron states into the structure is used to investigate the effects on the current transport behavior within the quantum Wigner phase space picture. Quantum effects are outlined by using classical simulation results as a reference frame. The utilized signed particle approach inherently provides a seamless transition between the classical and quantum domain. Based on this the occurring quantum effects caused by the non‐locality of the action of the quantum potential, leading to spatial resonance, can be indentified. The resulting interference patterns enable novel applications in the area of entangletronics. 相似文献
The curious dual nature of the neutron, sometimes a particle, sometimes a wave, is wonderfully manifested in the various non-local
interference and quantum contextuality effects observed in neutron interferometry. Non-classical states may become useful
for novel fundamental and solid state research. Here we discuss unavoidable quantum losses as they appear in neutron phase-echo
and spin rotation experiments and we show how entanglement effects in a single particle system demonstrate quantum contextuality.
In all cases of interactions, parasitic beams are produced which cannot be recombined completely with the original beam. This
means that a complete reconstruction of the original state would, in principle, be impossible which causes a kind of intrinsic
irreversibility. Even small interaction potentials can have huge effects when they are applied in quantum Zeno-like experiments.
Recently, it has been shown that an entanglement between external and internal degrees of freedom exists even in single particle
systems. This contextuality phenomenon also shows that a quantum system carries much more information than usually extracted.
The path towards advanced neutron quantum optics will be discussed.
相似文献
The longitudinal response functions are used to generalize the dispersion properties of electron acoustic waves (EAWs) in the presence of quantum recoil, for isotropic, non‐relativistic, degenerate/non‐degenerate plasmas. In order to study the EAWs, the constituents of non‐degenerate (thermal) plasma are considered to be of two groups of electrons having different number density and temperature, namely the cold electrons and the hot electrons. Similarly in degenerate (Fermi) plasma the two population of electrons are considered to be the thinly populated and the thickly populated electrons. The sparsely populated electrons are termed as cold electrons while the densely populated ones are termed as hot electrons. The ions are stationary which form the neutralizing background. The absorption coefficients for Landau damping with the inclusion of the quantum recoil in both plasmas are calculated and discussed. The results are discussed in the context of laser‐produced plasma. 相似文献
A key resource for quantum optics experiments is an on‐demand source of single and multiple photon states at telecommunication wavelengths. This letter presents a heralded single photon source based on a hybrid technology approach, combining high efficiency periodically poled lithium niobate waveguides, low‐loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro‐optic switches. Hybrid interfacing different platforms is a promising route to exploiting the advantages of existing technology and has permitted the demonstration of the multiplexing of four identical sources of single photons to one output. Since this is an integrated technology, it provides scalability and can immediately leverage any improvements in transmission, detection and photon production efficiencies. 相似文献
Controlling spontaneous emission (SE) is of fundamental importance to a diverse range of photonic applications including but not limited to quantum optics, low power displays, solar energy harvesting and optical communications. Characterized by photonic bandgap (PBG) property, three‐dimensional (3D) photonic crystals (PCs) have emerged as a promising synthetic material, which can manipulate photons in much the same way as a semiconductor does to electrons. Emission tunable nanocrystal quantum dots (QDs) are ideal point sources to be embedded into 3D PCs towards active devices. The challenge however lies in the combination of QDs with 3D PCs without degradation of their emission properties. Polymer materials stand out for this purpose due to their flexibility of incorporating active materials. Combining the versatile multi‐photon 3D micro‐fabrication techniques, active 3D PCs have been fabricated in polymer‐QD composites with demonstrated control of SE from QDs. With this milestone novel miniaturized photonic devices can thus be envisaged. 相似文献
We proposed a simplified model to describe the excitonic effect on electron tunneling through a quantum well (QW). Using nonequilibrium-Green-function method self consistently, we calculated the dc current of electron tunneling through QW. The extra plateau in the J-V characteristics appears dearly, which shows the existence of exciton in QW. This result is in good agreement with the experiment qualitatively. We also studied the density of electrons and holes in the quantum well. 相似文献
Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi
level of the quantum dot is set by the conduction electrons of the leads, we
calculate the electron current from the left side by assuming the quantum
dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively. 相似文献
Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quantum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ??paper-cutting?? technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots. These quasi-one-dimensional (nanoribbons) and quasi-zero-dimensional (quantum dots) graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, we emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperfine interaction in graphene. 相似文献
The development of dynamic single-electron sources has made it possible to observe and manipulate the quantum properties of individual charge carriers in mesoscopic circuits. Here, we investigate multi-particle effects in an electronic Mach–Zehnder interferometer driven by a series of voltage pulses. To this end, we employ a Floquet scattering formalism to evaluate the interference current and the visibility in the outputs of the interferometer. An injected multi-particle state can be described by its first-order correlation function, which we decompose into a sum of elementary correlation functions that each represent a single particle. Each particle in the pulse contributes independently to the interference current, while the visibility (given by the maximal interference current) exhibits a Fraunhofer-like diffraction pattern caused by the multi-particle interference between different particles in the pulse. For a sequence of multi-particle pulses, the visibility resembles the diffraction pattern from a grid, with the role of the grid and the spacing between the slits being played by the pulses and the time delay between them. Our findings may be observed in future experiments by injecting multi-particle pulses into a Mach–Zehnder interferometer. 相似文献
Quantum optics plays a central role in the study of fundamental concepts in quantum mechanics, and in the development of new technological applications. Typical experiments employ sources of photon pairs generated by parametric processes such as spontaneous parametric down‐conversion and spontaneous four‐wave‐mixing. The standard characterization of these sources relies on detecting the pairs themselves and thus requires single photon detectors, which limit both measurement speed and accuracy. Here it is shown that the two‐photon quantum state that would be generated by parametric fluorescence can be characterised with unprecedented spectral resolution by performing a classical experiment. This streamlined technique gives access to hitherto unexplored features of two‐photon states and has the potential to speed up design and testing of massively parallel integrated nonlinear sources by providing a fast and reliable quality control procedure. Additionally, it allows for the engineering of quantum light states at a significantly higher level of spectral detail, powering future quantum optical applications based on time‐energy photon correlations. 相似文献
In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. (QD) which a.re necessary to the nnderstanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantmn emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as opti- cal properties of the QDs. We then review the localizatioll of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and perfornances in terms of strong coupling regime, elfieiency, directionality, and polarization control. Furthermore, we will discuss the recenl, progress on the fabrication of single photon sources, and various a.pproaehes for embedding single QDs into mieroca,vities or photonic crystal nanoeavities and show how to ex- tend the wavelength range. We focus in part;icular on new generations of electrically driven QD single photon source leading to high repetition rates, efficiencies at elevated temperature operation. Besides strong eoupling regime, and high collection new development;s of room temperature sin- gle photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for pract ical single-photon sources are also discussed. 相似文献
During the current flat-top phase of electron cyclotron
resonance heating discharges in the HL-2A Tokamak, the behaviour of
runaway electrons has been studied by means of hard x-ray detectors
and neutron diagnostics. During electron cyclotron resonance
heating, it can be found that both hard x-ray radiation intensity
and neutron emission flux fall rapidly to a very low level, which
suggests that runaway electrons have been suppressed by electron
cyclotron resonance heating. From the set of discharges studied in
the present experiments, it has also been observed that the
efficiency of runaway suppression by electron cyclotron resonance
heating was apparently affected by two factors: electron cyclotron
resonance heating power and duration. These results have been
analysed by using a test particle model. The decrease of the
toroidal electric field due to electron cyclotron resonance heating
results in a rapid fall in the runaway electron energy that may lead
to a suppression of runaway electrons. During electron cyclotron
resonance heating with different powers and durations, the runaway
electrons will experience different slowing down processes. These
different decay processes are the major cause for influencing the
efficiency of runaway suppression. This result is related to the
safe operation of the Tokamak and may bring an effective control of
runaway electrons. 相似文献