Susan M. Clark

Quantum Computers Based on Electron Spins Controlled by Ultrafast Off-Resonant Single Optical Pulses

We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

Ultrafast Optical Spin Echo for Electron Spins in Semiconductors

Spin-based quantum computing and magnetic resonance techniques rely on the ability to measure the coherence time T(2) of a spin system. We report on the experimental implementation of all-optical spin echo to determine the T(2) time of a semiconductor electron-spin system. We use three ultrafast optical pulses to rotate spins an arbitrary angle and measure an echo signal as the time between pulses is lengthened. Unlike previous spin-echo techniques using microwaves, ultrafast optical pulses allow clean T(2) measurements of systems with dephasing times (T_{2};{*}) fast in comparison to the time scale for microwave control. This demonstration provides a step toward ultrafast optical dynamic decoupling of spin-based qubits.

Coherent error suppression in multiqubit entangling gates.

We demonstrate a simple pulse shaping technique designed to improve the fidelity of spin-dependent force operations commonly used to implement entangling gates in trapped ion systems. This extension of the Mølmer-Sørensen gate can theoretically suppress the effects of certain frequency and timing errors to any desired order and is demonstrated through Walsh modulation of a two qubit entangling gate on trapped atomic ions. The technique is applicable to any system of qubits coupled through collective harmonic oscillator modes.

Ultrafast control of donor-bound electron spins with single detuned optical pulses

A technique that controls electron spins using single optical pulses far detuned from the optical transition has been demonstrated. This approach may enable fast spin manipulation in a variety of solid-state systems.

Millisecond spin-flip times of donor-bound electrons in GaAs

We observe millisecond spin-flip relaxation times of donor-bound electrons in high-purity

Assembling a ring-shaped crystal in a microfabricated surface ion trap

n\text{\ensuremath{-}}\mathrm{GaAs}

Photon antibunching and magnetospectroscopy of a single fluorine donor in ZnSe

. This is three orders of magnitude larger than previously reported lifetimes in

Optically controlled semiconductor spin qubits for quantum information processing

n\text{\ensuremath{-}}\mathrm{GaAs}

Trapped ions for testing foundations of quantum theory

. Spin-flip times are measured as a function of magnetic field and exhibit a strong power-law dependence for fields greater than

Spin echo of electron spins in semiconductors using ultrafast, small-angle, optical pulses

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