Improving a solid-state qubit through an engineered mesoscopic environment

Abstract

A controlled quantum system can alter its environment by feedback, leading to reduced-entropy states of the environment and to improved system coherence. Here, using a quantum dot electron spin as control and probe, we prepare the quantum dot nuclei under the feedback of coherent population trapping and measure the evolution from a thermal to a reduced-entropy state, with the immediate consequence of extended qubit coherence. Via Ramsey interferometry on the electron spin, we directly access the nuclear distribution following its preparation, and measure the emergence and decay of correlations within the nuclear ensemble. Under optimal feedback, the inhomogeneous dephasing time of the electron, $T_2^{\ast }$, is extended by an order of magnitude to $39$~ns. Our results can be readily exploited in quantum information protocols utilizing spin-photon entanglement, and represent a step towards creating quantum many-body states in a mesoscopic nuclear spin ensemble.

6 pages, 3 figures

References in corpus (6)

• Nuclear spin physics in quantum dots: an optical investigation
• Enhancing the Coherence of a Spin Qubit by Operating it as a Feedback Loop That Controls its Nuclear Spin Bath
• Dynamics of Quantum Dot Nuclear Spin Polarization Controlled by a Single Electron
• Demagnetization of Quantum Dot Nuclear Spins: Breakdown of the Nuclear Spin Temperature Approach
• Efficient dynamical nuclear polarization in quantum dots: Temperature dependence
• Nuclear Tuning and Detuning of the Electron Spin Resonance in a Quantum Dot

Cited by in corpus (1)

• Protocol for generating multi-photon entangled states from quantum dots in the presence of nuclear spin fluctuations