AIP conference proceedings

Spin coherent read, write, manipulation of electrons with light in solids

Hideo Kosaka, Hideki Shigyou, Takeshi J. Inagaki, Yasuyoshi Mitsumori, Keiichi Edamatsu, Takeshi Kutsuwa, M. Kuwahara, Keiji Ono, Yoshiaki Rikitake, Nobuhiko Yokoshi, Hiroshi Imamura, Timothy C. Ralph, Ping Koy Lam

Published Jan 1, 2011• 0 citations

Publisher

Abstract

Spin is a quantum property of electrons. For spin‐based quantum information technology, preparation and read‐out of the electron spin state should be spin coherent. We demonstrate that the polarization coherence of light can be transferred to the spin coherence of electrons in a semiconductor quantum nanostructure, and the prepared coherence of the electron spin can also be read out with light by the developed tomographic Kerr rotation method. We also demonstrate that a single photon is efficiently converted (∼27%) into a single electron trapped in a gate‐defined quantum dot, where the g‐factor of electrons is tuned to zero, and the charge state is detected with an adjacent quantum point contact without destructing the spin state. We further demonstrate that the spin coherence of a single electron trapped in one of double quantum dots is electrically manipulated with a microwave applied to the gate and read out via the Pauli spin blockade phenomenon. All of these functions are needed to build all semiconductor quantum repeaters and distributed quantum computers.

DOI: 10.1063/1.3630172

Related papers

Coherent spin preparation, manipulation and read-out with light and microwaves in a quantum well and dot

Hideo Kosaka, Hideki Shigyou, Takahiro Inagaki +8 more

Spin is a quantum property of electrons. For spin-based quantum information technology, preparation and read-out of the electron spin state should be spin coherent. We demonstrate that the polarization coher ence of light can be transferred to the spin coherence of electrons in a semiconductor quantum nanostructure [1], and the prepared coherence of the electron spin can also be read out with light by the developed tomographic Kerr rotation method [2]. We also demonstrate that a single photon is efficiently converted (~27%) into a single electron trapped in a gate-defined quantum dot, where the g-factor of electrons is tuned to zero, and the charge state is detected with an adjacent quantum point contact without destructing the spin state [3]. We further demonstrate that the spin coherence of a single electron trapped in one of double quantum dots is electrically manipulated with a microwave applied to the gate and read out via the Pauli spin blockade phenomenon [4]. These demonstrations were carried out in a condition where the up/down spin basis states of electrons remain ed degenerated under an in-plain magnetic field. As this condition ensures the energy conservation between photons and electrons, the entire Poincare sphere representing polarization states of photons can be mapped onto the Bloch sphere representing spin polar ization states of electrons. We theoretically showed that relative spin coherence of two electrons can be also measured with the help of spin-flip tunneling of electrons between the dots [5]. Full Bell state measurement is also possible by the single -spin manipulation and Pauli spin blockade [6]. All of these functions are needed to build all semiconductor quantum repeaters and distributed quantum computers.

Journal of Physics Conference SeriesSep 1, 20101 citation

Photon-to-electron quantum information transfer

Hideo Kosaka

Spin is a fundamental property of electrons and plays an important role in information storage. For spin-based quantum information technology, preparation and read-out of the electron spin state must be spin coherent, but both the traditional preparation and read-out of the spin state are projective to up/down spin states, which do not have spin coherence. We have recently demonstrated that the polarization coherence of light can be coherently transferred to the spin coherence of electrons in a semiconductor. We have also developed a new scheme named tomographic Kerr rotation (TKR) by generalizing the traditional KR to directly read out the spin coherence of optically prepared electrons without the need for the spin dynamics, which allows the spin projection measurement in an arbitrary set of basis states. These demonstrations were performed using g-factor-controlled semiconductor quantum wells with precessing and non-precessing electrons. The developed scheme offers a tool for performing basis-independent preparation and read-out of a spin quantum state in a solid. These results encourage us to make a quantum media converter between flying photon qubits and stationary electron spin qubits in semiconductors.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEFeb 10, 20110 citations

Photon-to-electron quantum information transfer

Hideo Kosaka

Spin is a fundamental property of electrons and plays an important role in information storage. For spin-based quantum information technology, preparation and read-out of the electron spin state must be spin coherent, but both the traditional preparation and read-out of the spin state are projective to up/down spin states, which do not have spin coherence. We have recently demonstrated that the polarization coherence of light can be coherently transferred to the spin coherence of electrons in a semiconductor. We have also developed a new scheme named tomographic Kerr rotation (TKR) by generalizing the traditional KR to directly readout the spin coherence of optically prepared electrons without the need for the spin dynamics, which allows the spin projection measurement in an arbitrary set of basis states. These demonstrations were performed using g-factor-controlled semiconductor quantum wells with precessing and nonprecessing electrons. The developed scheme offers a tool for performing basis-independent preparation and read-out of a spin quantum state in a solid. These results encourage us to make a quantum media converter between flying photon qubits and stationary electron spin qubits in semiconductors.

Journal of Applied PhysicsMay 15, 201111 citations

Free spin quantum computation with semiconductor nanostructures

Weimin Zhang, Yin‐Zhong Wu, Chopin Soo

Taking the excess electron spin in a unit cell of semiconductor multiple quantum-dot structure as a qubit, we can implement scalable quantum computation without resorting to spin-spin interactions. The technique of single electron tunnelings and the structure of quantum-dot cellular automata (QCA) are used to create a charge entangled state of two electrons which is then converted into spin entanglement states by using single spin rotations. Deterministic two-qubit quantum gates can also be manipulated using only single spin rotations with help of QCA. A single-short read-out of spin states can be realized by coupling the unit cell to a quantum point contact.

arXiv:quant-ph/0502002Feb 1, 20051 citation

Coherent transfer of spin and entanglement in optoelectronics

Verónica Cerletti

In the last few years there has been a growing interest in the possible applications of quantum properties of different physical systems in well established technologies. This was motivated by the miniaturization of electronic devices. For very small systems, the laws of quantum mechanics start to govern their behavior and it is then to expect that for instance electronic components reach their "quantum limit". A good example of the introduction of quantum properties into conventional technologies is the case of the electron spin, which offers an alternative to electron-charge for the storage and transport of information in electronics. The idea of using electron spins in electronics gave rise to the new and exciting field of spintronics and was encouraged by experiments that showed coherent spin transport over long distances (over hundred micrometers) in semiconductors and long electron spin dephasing times. In addition to its applications in conventional technologies, the use of the electron spin as information-carrier has been suggested for the new field of quantum information processing. An important advantage of the electron spin with respect to other quantum information-carriers proposed is that it can profit from the well developed semiconductor industry and its related technologies. For the long-range transport of information, however, the highly interacting environment in solid-state devices represents a difficulty to the use of electron spins. In contrast, photons are very weekly coupled to their environment, and therefore more suitable for the transfer of information over long distances (on the order of kilometers), required, for instance, in quantum communication. Furthermore, the technology needed for the transport of photons over such long distances is well developed. Thus, an efficient transfer of quantum information between electron spins and photons is highly desirable. \n \nIn this dissertation, we show that the transfer of entanglement, a quantum correlation, from electron spins to the polarization of photons is not only theoretically possible, but also feasible under realistic experimental conditions. We study the transport of an entangled pair of electron spins through Fermi leads which split them spatially until they reach spin-LEDs, semiconductor structures containing quantum dots. In these structures, the electrons optically recombine with holes, producing then photons. We analyze the polarization state of the out-coming photons and give the conditions for which the entanglement of the electron spins is fully recovered in the photon-polarizations. We further show that it is possible to produce four-photon entanglement. \n \nWe also include in this work the study of coherent spin-transfer between quantum dots layers bridged by molecules. This study was motivated by an experiment showing that the molecules act not only as binders to construct the multilayer structures, but also as "wires" for the information through electron spins in the quantum dots. We show that a two-site Hamiltonian captures some of the essential features of the experiment. We calculate the dependence of the experimentally observed Faraday rotation (FR) signal as a function of probe energy on microscopic parameters such as spin transfer probabilities. The Faraday angle is related to the difference in the dielectric response for different polarizations of the light. We calculate the dielectric response functions of coupled quantum dots and derive an analytical expression for the FR angle in terms of electron transfer probabilities and Heisenberg exchange splittings.

Jan 1, 20050 citations

Angular momentum transfer between a circularly polarized photon and an electron spin in double quantum dots

T. Asayama, T. Fujita, Haruki Kiyama +4 more

We propose an experimental scheme of photon‐spin quantum interface using a semiconductor double quantum dot. A polarized electron spin is excited by a circularly polarized photon. We detect the spin state applying Pauli spin blockade which is often employed to detect orientation of a single electron spin in double quantum dots.

AIP conference proceedingsJan 1, 20110 citations