arXiv subjects

S. J. Boyle

Publications and source records attributed to S. J. Boyle.

7 recordsLinked to original sources

arXiv2012

Coherent optical control of the spin of a single hole in a quantum dot

We demonstrate coherent optical control of a single hole spin confined to an InAs/GaAs quantum dot. A superposition of hole spin states is created by fast (10-100 ps) dissociation of a spin-polarized electron-hole pair. Full control of the hole-spin is achieved by combining coherent rotations about two axes: Larmor precession of the hole-spin about an external Voigt geometry magnetic field, and rotation about the optical-axis due to the geometric phase shift induced by a picosecond laser pulse resonant with the hole-trion transition.

cond-mat.mes-hall↗

arXiv2011

Effect of detuning on the phonon induced dephasing of optically driven InGaAs/GaAs quantum dots

Recently, longitudinal acoustic phonons have been identified as the main source of the intensity damping observed in Rabi rotation measurements of the ground-state exciton of a single InAs/GaAs quantum dot. Here we report experiments of intensity damped Rabi rotations in the case of detuned laser pulses, the results have implications for the coherent optical control of both excitons and spins using detuned laser pulses.

cond-mat.mes-hall↗

arXiv2010

Phonon induced Rabi frequency renormalization of optically driven single InGaAs/GaAs quantum dots

We study optically driven Rabi rotations of a quantum dot exciton transition between 5 and 50 K, and for pulse-areas of up to $14π$. In a high driving field regime, the decay of the Rabi rotations is nonmonotonic, and the period decreases with pulse-area and increases with temperature. By comparing the experiments to a weak-coupling model of the exciton-phonon interaction, we demonstrate that the observed renormalization of the Rabi frequency is induced by fluctuations in the bath of longitudinal acoustic phonons, an effect that is a phonon analogy of the Lamb-shift.

cond-mat.mes-hall↗

arXiv2010

Fast high fidelity hole spin initialization in a single InGaAs quantum dot

We demonstrate fast initialization of a single hole spin captured in an InGaAs quantum dot with a fidelity F>99% by applying a magnetic field parallel to the growth direction. We show that the fidelity of the hole spin, prepared by ionization of a photo-generated electron-hole pair, is limited by the precession of the exciton spin due to the anisotropic exchange interaction.

cond-mat.mes-hall↗

arXiv2009

Towards coherent optical control of a single hole spin: Rabi rotation of a trion conditional on the spin state of the hole

A hole spin is a potential solid-state q-bit, that may be more robust against nuclear spin induced dephasing than an electron spin. Here we propose and demonstrate the sequential preparation, control and detection of a single hole spin trapped on a self-assembled InGaAs/GaAs quantum dot. The dot is embedded in a photodiode structure under an applied electric-field. Fast, triggered, initialization of a hole spin is achieved by creating a spin-polarized electron-hole pair with a picosecond laser pulse, and in an applied electric-field, waiting for the electron to tunnel leaving a spin-polarized hole. Detection of the hole spin with picosecond time resolution is achieved a second picosecond laser pulse to probe the positive trion transition, where a trion is created conditional on the hole spin to be detected as a change in photocurrent. Finally, using this setup we observe a Rabi rotation of the hole-trion transition that is conditional on the hole spin, which for a pulse-area of $2π$ can be used to impart a phase-shift of $π$ between the hole spin states, a non-general manipulation of the hole spin.

cond-mat.mes-hall↗

arXiv2008

Fast optical preparation, control and read-out of single quantum dot spin

We propose and demonstrate the sequential initialization, optical control, and read-out of a single spin trapped in a semiconductor quantum dot. Hole spin preparation is achieved through ionization of a resonantly excited electron-hole pair. Optical control is observed as a coherent Rabi rotation between the hole and charged exciton states, which is conditional on the initial hole spin state. The spin-selective creation of the charged exciton provides a photocurrent read-out of the hole spin state.

cond-mat.mes-hall↗

arXiv2008

Two qubit conditional quantum logic operation in a single self-assembled quantum dot

The four-level exciton/biexciton system of a single semiconductor quantum dot acts as a two qubit register. We experimentally demonstrate an exciton-biexciton Rabi rotation conditional on the initial exciton spin in a single InGaAs/GaAs dot. This forms the basis of an optically gated two-qubit controlled-rotation (CROT) quantum logic operation where an arbitrary exciton spin is selected as the target qubit using the polarization of the control laser.

cond-mat.mes-hall↗