Spin pairing in quantum dots with many electrons

Thomas Grange, R. Ferreira, G. Bastard +4 more

G. Giavaras, J. H. Jefferson, M. Fearn +1 more

We propose a method of generating fully entangled electron spin pairs using an open static quantum dot and a moving quantum dot, realized by the propagation of a surface acoustic wave (SAW) along a quasi-one-dimensional channel in a semiconductor heterostructure. In particular, we consider a static dot (SD) loaded with two interacting electrons in a singlet state and demonstrate a mechanism which enables the moving SAW dot to capture and carry along one of the electrons, hence yielding a fully entangled static-flying pair. We also show how with the same mechanism we can load the SD with one or two electrons which are initially carried by a SAW-induced dot. The feasibility of realizing these ideas with existing semiconductor technology is demonstrated and extended to yield flying or static pairs that are fully entangled and arbitrary interconversion of static and flying electron spin qubits.

Tuukka Hiltunen

Özgür Çakır, T. Takagahara

We investigate quantum dynamics in the electron-nuclei coupled spin system in quantum dots and clarify the fundamental features of quantum correlation induced via successive electron-spin measurements. This quantum correlation leads to interesting phenomena such as the bunching of outcomes in the electron-spin measurements and the revival of an arbitrary initial electron-spin state. The nuclear spin system is also affected by the quantum correlation and is, in fact, squeezed via conditional measurements or postselection. This squeezing is confirmed by calculating the increase in the purity of the nuclear spin system. Thus, the successive electron-spin measurements provide a probabilistic method to squeeze the nuclear spin system. These new features are predicted not only for the case of double quantum dots occupied by a pair of electrons but also for the case of a single quantum dot occupied by a single electron or a pair of electrons.

Ilya V. Ponomarev, Matt Doty, Michael Scheibner +3 more

Monique Combescot, Odile Betbeder-Matibet, V. Voliotis

We here propose a mechanism to teleport electrons between quantum dots through the transformation of a virtual bright exciton into a dark exciton. This mechanism relies on the interactions of two composite bosons: a pair of electrons with opposite spins, trapped in two dots and an electron-hole pair in a free exciton coupled to an unabsorbed pump pulse, which makes it “bright” but virtual. This bright exciton first turns “dark” by dropping its electron and stealing the trapped electron with opposite spin through an exchange Coulomb process with the trapped pair. In a second step, the dark exciton “flies” with its electron to the other dot where it turns bright again, by the inverse process. The “Shiva diagrams” for composite-boson many-body effects that we have recently introduced, enlighten this understanding.