Quantum-Dot Spin-State Preparation with Near-Unity Fidelity

Abstract

We have demonstrated laser cooling of a single electron spin trapped in a semiconductor quantum dot. Optical coupling of electronic spin states was achieved using resonant excitation of the charged quantum dot (trion) transitions along with the heavy-light hole mixing, which leads to weak yet finite rates for spin-flip Raman scattering. With this mechanism, the electron spin can be cooled from 4.2 to 0.020 kelvin, as confirmed by the strength of the induced Pauli blockade of the trion absorption. Within the framework of quantum information processing, this corresponds to a spin-state preparation with a fidelity exceeding 99.8%.

Coherent population trapping of an electron spin in a single negatively charged quantum dot

“…We set the gate voltage at the edge of the trion charge plateau, where the optical pumping of the electron spin effect is suppressed [15,16]. The main figure in Fig respectively, which are similar to the g factors reported in the literature [5,15].…”

“…Electron spin state initialization has recently been realized in a single QD by optical spin cooling techniques with a high fidelity [15,16]. However, the limitation is that only two possible initial qubit states can be prepared, either spin up or spin down.…”

Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

“…S ignificant progress has been reported within quantum information science for quantum-dot (QD) spins as stationary qubits 1,2 , including state preparation 3,4 , long spin-coherence times 5,6 , ultrafast optical manipulation capabilities 7,8 and single-shot read-out 9 . A successful realization of a solid-state quantum network relies on scalable entangling gates between individual spins.…”

Quantum Computing with Spins in Solids

“…Depending on the particular architechture, this may take a long time or it may be inconvenient to have large magnetic fields in the region of the apparatus. Initialization could also be achieved through spin-injection from a ferromagnet, as has been performed in bulk semiconductors (Fiederling et al 1999, Ohno et al 1999, with a spin-polarized current from a spin-filter device (Prinz and Hathaway 1995, Prinz 1998, Loss and DiVincenzo 1998, DiVincenzo 1999, Recher et al 2000, or by optical pumping (Cortez et al 2002, Shabaev et al 2003, Gywat et al 2004, which has now allowed the preparation of spin states with very high fidelity, in one case as high as 99.8% (Atature et al 2006).…”