Generation of electron entanglement in quantum dot systems

Abstract

We propose a solid-state quantum structure capable of generating EinsteinPodolsky-Rosen (EPR) electron pairs using a parametric electron pumping idea and the Coulomb blockade phenomenon. The quantum structure consists of two coupled quantum dots and four leads. Our scheme is easy to implement, and it does not impose special requirements on the leads. By employing the parametric pumping idea, harmful processes can be avoided and only two quantum dots are needed. Furthermore, the EPR electron pairs are spatially separated.(Some figures in this article are in colour only in the electronic version) Quantum entanglement is a natural resource for quantum computation and quantum information [1]. The future development of quantum information and quantum computation depends largely on how effectively one can generate and process entangled states of different objects. So far, most experiments on quantum information processes, such as quantum cryptography [2] and quantum teleportation [3], have been done by using entangled EPR photon pairs. The entangled trapped ions and atoms also provide a means for the possible realization of quantum information and quantum computation [4,5]. However, it should be more interesting and important in terms of applications to generate electron spin entanglement in solid state systems [6][7][8][9][10][11][12][13][14]. The usefulness of electron spin entanglement has been assured by the recent demonstration of long electron spin lifetime in semiconductors [15,16]. Several methods [6][7][8][9][10][11]17] for entanglement generation as well as entanglement detection in solid state systems have been proposed. Beam splitters [6], devices based on BCS superconductors [12,13], and the two-dimensional interacting electron gas [14] are some examples. There are also proposals involving quantum dots (QDs) in generating entanglement

Full counting statistics of level renormalization in electron transport through double quantum dots

“…Coupling of the double dots to an external phonon bath leads to dephasing and relaxation mechanisms, which are shown to suppress noise notably. Furthermore, double dot systems, as recently shown in [54,55], are good candidates for entanglement generation. In this context, the present full counting statistics have the potential to facilitate the identification and characterization of entanglement originating from different sources.…”

“…Furthermore, double dot systems, as recently shown in Refs. [54,55], are good candidates for entanglement generation. In this context, the present full counting statistics have the potential to facilitate the identification and characterization of entanglement originating from different sources.…”

Self-sustained current oscillations in spin-blockaded quantum dots

“…1(c), in the presence of interdot tunneling at finite external field, the spin triplets are below the singlet state |S by an energy J depending on source-drain bias. 7,13,14,20 Increasing the external field will lift the triplet degeneracy, and |S and |T − states anticross at a field B r around 0.5 T. 6 Due to the spin blockade and weak coupling of dots with two leads, a leakage current of order of 1 pA, corresponding to 100 ns electron tunneling time, exists. The current experiences a jump near B r because spin blockade is partially removed by spin flipping and the transition from configuration D to B is possible.…”

“…As shown in Fig. 1c, three triplet states (|T 0 >, |T ±1 >) are degenerated in the absence of an external magnetic field, and are below the spin singlet state |S > by an energy J [12], order of inter-dot exchange energy. Due to the spin blockade and weak coupling of dots with two leads, a leakage current of order of 1pA, corresponding to 100ns electron tunneling time, exists.…”

Cotunnelling versus sequential tunnelling in Coulomb blockade metallic double quantum dot structures

“…However, currently, its quantitative description is mostly limited to single QD structures. Recently, the double quantum dot structures have been strongly suggested as the most prospective candidate for a solid state qubit [11][12][13], and therefore have become a very attractive object of both experimental [14] and theoretical [15][16][17][18] investigations. In the structure where two quantum dots are embedded between three tunnel junctions (figure 1(a)), two dominant tunnelling processes are the ST and the two-electron cotunnelling (2ECT).…”