Optical Spin Echo

Introduction

Ultrafast optical pulses can be used to prevent qubit decoherence by the spin-echo pulse sequence, similar to past experiments in NMR.

This project demonstrates how the coherence time of an electron spin in a single quantum dot can be increased by 1000× by applying a pulse at an appropriate time such re-phasing (in the time ensemble) occurs. A T₂ coherence time of ~3 microseconds is measured, which means that the “memory lifetime” of the qubit is about 10⁵× longer than the time it takes to apply a single arbitrary axis rotation operation.

Figure 1. Fringe heights decay as a coarse delay between two \pi/2 pulses is increased, which is characteristic of a decoherence process. The fit of the decay yields the coherence time.

Publications

Press et al. “Ultrafast optical spin echo in a single quantum dot.” Nature Photonics 4, 367 – 370 (2010). [http://dx.doi.org/10.1038/nphoton.2010.83]

Project Members

Dr. David Press

Kristiaan De Greve

Dr. Thaddeus Ladd

Prof. Yoshihisa Yamamoto

External Collaborators

Funding Acknowledgments

Ultrafast Optical Control of Spin Qubits

Broadband optical pulses provide picosecond-scale control of a spin qubit.

Nuclear Bath Interaction with a Spin Qubit

Optical pulses show a nonlinear feedback effect between spin qubit and nuclear environment.