Samuel Carter

Ultrafast optical control of entanglement between two quantum-dot spins

Optical control over electron spins embedded in semiconductor structures is an efficient way of manipulating quantum information. But a fully fledged quantum information processor will require control over two-spin states. This has now been demonstrated, including the implementation of ‘ultrafast’ two-qubit gate operations that take less than a nanosecond.

Optical control of one and two hole spins in interacting quantum dots

Researchers demonstrate fast, single-qubit gates using a sequence of 13 ps pulses. Two vertically stacked InAs/GaAs quantum dots were coupled through coherent tunnelling and charged with controlled numbers of holes. The interaction between hole spins was investigated by Ramsey fringe experiments, showing a tunable interaction range of tens of gigahertz.

Quantum control of a spin qubit coupled to a photonic crystal cavity

Using a long-lived quantum-dot spin qubit coupled to a GaAs-based photonic crystal cavity, researchers demonstrate complete quantum control of an electron spin qubit. By cleverly controlling the charge state of the InAs quantum dot using laser pulses, optical initialization, control and readout of an electron spin are achieved.

Spin coherence and echo modulation of the silicon vacancy in4H−SiCat room temperature

The silicon vacancy in silicon carbide is a strong emergent candidate for applications in quantum information processing and sensing. We perform room temperature optically-detected magnetic resonance and spin echo measurements on an ensemble of vacancies and find the properties depend strongly on magnetic field. The spin echo decay time varies from less than 10

Leveraging Crystal Anisotropy for Deterministic Growth of InAs Quantum Dots with Narrow Optical Linewidths

\mu

Directing nuclear spin flips in InAs quantum dots using detuned optical pulse trains.

s at low fields to 80

Spin–cavity interactions between a quantum dot molecule and a photonic crystal cavity

\mu

Strong hyperfine-induced modulation of an optically driven hole spin in an InAs quantum dot

s at 68 mT, and a strong field-dependent spin echo modulation is also observed. The modulation is attributed to the interaction with nuclear spins and is well-described by a theoretical model.

Picosecond pulse shaping of single photons using quantum dots

Crystal growth anisotropy in molecular beam epitaxy usually prevents deterministic nucleation of individual quantum dots when a thick GaAs buffer is grown over a nanopatterned substrate. Here, we demonstrate how this anisotropy can actually be used to mold nucleation sites for single dots on a much thicker buffer than has been achieved by conventional techniques. This approach greatly suppresses the problem of defect-induced line broadening for single quantum dots in a charge-tunable device, giving state-of-the-art optical linewidths for a system widely studied as a spin qubit for quantum information.

Controlling the Nuclear Polarization in Quantum Dots Using Optical Pulse Shape with a Modest Bandwidth

We demonstrate that the sign of detuning of an optical pulse train from quantum dot resonances controls the direction of nuclear spin flips. This effect can produce a narrow, precise distribution of nuclear spin polarizations.