Entanglement Between a Single Quantum Dot Spin and a Single Photon

Weibo Gao, P. Fallahi, Emre Togan +2 more

John R. Schaibley, A. P. Burgers, Greg McCracken +6 more

Leo Yu, Jason S. Pelc, Kristiaan De Greve +13 more

We report an ultrafast downconversion quantum interface, where 910-nm single photons from a quantum dot are downconverted to the 1.5-µm telecom band with sub-10 picosecond pulses at 2.2-µm, enabling the demonstration of quantum-dot spin-photon entanglement.

Gabriel González, Michael Niklaus Leuenberger, Hubert Pascal Seigneur +1 more

We review our theoretical proposal on producing a scalable quantum network inside a photonic crystal. The qubits are represented by electron spins in quantum dots, each embedded inside a nanocavity that is produced by a defect in the photonic crystal. The coupling between the qubits is governed by single photons that are guided through waveguides in the photonic crystal, thereby interacting with the quantum dots by means of the conditional single-photon Faraday rotation, which provides the basic method to entangle single spins with single photons. Unlike other schemes using virtual photons, our scheme makes use of real single photons that produce the spin entanglement. Therefore all the spin-photon interactions can be performed locally at each site of a quantum dot, which is a key ingredient for making our quantum network scalable. Copyright © 2010 American Scientific Publishers All rights reserved.

Ataç İmamoğlu

Cong-Yuan Hu, William J. Munro, Jeremy L. O’Brien +1 more

Semiconductor quantum dots (known as artificial atoms) hold great promise for solid-state quantum networks and quantum computers. To realize a quantum network, it is crucial to achieve light-matter entanglement and coherent quantum-state transfer between light and matter. Here we present a robust photon-spin entangling gate with high fidelity and high efficiency (up to 50 percent) using a charged quantum dot in a double-sided microcavity. This gate is based on giant circular birefringence induced by a single electron spin, and functions as an optical circular polariser which allows only one circularly-polarized component of light to be transmitted depending on the electron spin states. We show this gate can be used for single-shot quantum non-demolition measurement of a single electron spin, and can work as an entanglement filter to make a photon-spin entangler, spin entangler and photon entangler as well as a photon-spin quantum interface. This work allows us to make all building blocks for solid-state quantum networks with single photons and quantum-dot spins.