Induced Quantum Dots and Wires: Electron Storage and Delivery

Abstract

We show that quantum dots and quantum wires are formed underneath metal electrodes deposited on a planar semiconductor heterostructure containing a quantum well. The confinement is due to the self-focusing mechanism of an electron wave packet interacting with the charge induced on the metal surface. Induced quantum wires guide the transfer of electrons along metal paths and induced quantum dots store the electrons in specific locations of the nanostructure. Induced dots and wires can be useful for devices operating on the electron spin.PACS numbers: 73.21. La,73.63.Nm Planar nanodevices containing single [1,2,3,4,5,6], double [7,8,9,10], and multiple [11,12] laterally coupled quantum dots with confinement potential tuned by electrodes deposited on top of the semiconductor heterostructure are at present extensively studied in both theory and experiment in context of application for quantum gates using electron spins as quantum bits. Recent advances include demonstration that the electron spin can be set and read-out [2,4,5,6,7,8,9,13] as well as rotated [6,13]. In a quantum gate working on the electron spins [14] the single qubit operations are to be performed with an electron transfer to a high g factor region or to a ferromagnetic quantum dot where the electron spin is rotated by microwave radiation. In this letter we present an idea for the control of the electron localization and its transfer between specific locations within the nanodevice. The idea is based on the self-focusing mechanism of an electron wave packet near a conductor surface [15,16,17] which as we show below allows to exclude scattering during the electron transfer and warrants the electron delivery to a specific location in the device with a 100% probability.In the conventional planar nanodevices [1, 2] a negative potential is applied to the gate electrodes to deplete the two-dimensional electron gas underneath. In the variant of the structure proposed below the role of the electrodes is different: a single quantum-well-confined electron becomes self-trapped below the conductor by the potential of the charge that it induces on the metal surface. The response potential of the electron gas of the conductor contains a component of lateral confinement which localizes the quantum-well-confined electron in form of a wave packet that moves parallel to the metal preserving its shape as an electron soliton [15,16]. The packed was called [17] an inducton since the focusing potential stems from the charge induced in the electron gas. The inducton possesses mixed quantum and classical properties. It is described by a wave function of both spatial and spin coordinates whose time evolution is described by the Schroedinger equation. On the other hand the inducton moves as a stable wave packet of a finite size and its transition probability in transport through potential barriers is binary (0 or 1) [16]. In Ref.[16] we discussed a structure of planar infinite layers of metal, insulator (or semiconducting blocking barrier) and a quantum well in which the i...

Nanodevice for High Precision Readout of Electron Spin

“…The self-focusing effect of the wave function occurs [8]. As the result the electron is trapped beneath the metal electrode forming a stable wave packet, which exhibits finite spatial extent and conserves its shape as it travels along the path determined by the electrode [9]. Such wave packet shows features unique for a quantum particle to have, as it reflects from a potential barrier or tunnels through it with probability of 1 like a classical object.…”

Comparaison of the Optical Anisotropy of Corrugated and NonCorrugated (311) Superlattices

“…In summary, we have studied theoretically the electronic and optical properties of non-corrugated (311) (GaAs) 8 /(AlAs) 8 superlattice and corrugated (311) (GaAs) 16 /(AlAs) 16 superlattices, using the empirical tightbinding model with realistic parameters determined from the bulk bands. Then we have compared the optical anisotropy of corrugated and non-corrugated (311) superlattices…”

Spin-Orbit-Mediated Manipulation of Heavy-Hole Spin Qubits in Gated Semiconductor Nanodevices

“…It has the unique property for a quantum particle, that it reflects from a barrier or tunnels through it with 100% probability while conserving its shape, which is rather a characteristic of classical objects. This property can be used to transfer a charged particle in the form of a stable wave packet (soliton) between different locations within the nanodevice by applying static weak voltages to the electrodes only [39]. We use a system of coordinates in which the quantum well is oriented in the z[001] (growth) direction and the hole can move only in the x[100] − y[010] plane.…”

“…The potential is found by solving the Poisson equation in a three dimensional computational box containing the entire nanodevice. The detailed method was described in Refs [17,39]. Quantum calculations [41] indicate that this is a good approximation of the actual response potential of the electron gas.…”