Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Frontiers in Optics

Controlled Rotation (C-ROT) Gate in a Single Self- Assembled Quantum Dot

Stephen J. Boyle, A. J. Ramsay, A. M. Fox, Maurice S. Skolnick, Hiu Yun Liu, M. Hopkinson

Published Jan 1, 2008• 0 citations
Publisher

Abstract

We demonstrate conditional Rabi rotations on the exciton-biexciton transition in a single self- assembled InGaAs/GaAs quantum dot using picosecond optical excitation and photocurrent readout. This is an implementation of the two-qubit C-ROT quantum logic gate.
DOI
10.1364/fio.2008.ftuc5

Related papers

Controlled-rotation quantum logic gate in a single self-assembled quantum dot

S. J. Boyle, A. J. Ramsay, A. M. Fox +3 more

We demonstrate conditional exciton-biexciton Rabi rotations in a single self-assembled InGaAs quantum dot using picosecond optical excitation and photocurrent readout, thereby implementing a two-qubit controlled-rotation (C-rot) quantum logic gate. ©2008 Optical Society of America.

Conference on Lasers and Electro-Optics•May 4, 2008•0 citations

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

S. J. Boyle, A. J. Ramsay, Frank Bello +4 more

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.

arXiv:0802.4368•Physical Review B•Aug 1, 2008•63 citations

An All-Optical Quantum Gate in a Semiconductor Quantum Dot

Xiaoqin Li, Yanwen Wu, Duncan G. Steel +6 more

We report coherent optical control of a biexciton (two electron-hole pairs), confined in a single quantum dot, that shows coherent oscillations similar to the excited-state Rabi flopping in an isolated atom. The pulse control of the biexciton dynamics, combined with previously demonstrated control of the single-exciton Rabi rotation, serves as the physical basis for a two-bit conditional quantum logic gate. The truth table of the gate shows the features of an all-optical quantum gate with interacting yet distinguishable excitons as qubits. Evaluation of the fidelity yields a value of 0.7 for the gate operation. Such experimental capability is essential to a scheme for scalable quantum computation by means of the optical control of spin qubits in dots.

Science•Aug 8, 2003•899 citations

Quantum-bit rotations in single quantum dots: Rabi oscillations of excitons and biexcitons

Xiaoqin Li, Todd H. Stievater, Yanwen Wu +1 more

Summary form only given. We use transient nonlinear optical spectroscopy to demonstrate Rabi oscillations between each of the dipole coupled states, corresponding to qubit rotations. The interface fluctuation GaAs quantum dots are probed with sub-micron spatial resolution. The resonant excitation of the biexciton requires a two-color scheme in a hyper Raman gain configuration. To demonstrate exciton Rabi oscillations, the laser wavelength is fixed at the exciton resonance. Exciton and biexciton Rabi oscillations correspond to qubit rotations of the |00> to |01> or |10> state and the |01> or |10> to |11> state respectively, depending on the polarization of the excitation field.

Quantum Electronics and Laser Science Conference•Jun 25, 2003•0 citations

Optical Coherent Control of a Single Charged Indium Arsenide Quantum Dot.

Katherine Truex

Optically driven self-assembled quantum dots are leading candidates for use in quantum computers because of their potential for high speed gate operations and relatively compact design. In this approach, each dot is charged with a single electron whose spin serves as the quantum bit (qubit). This thesis addresses the need for a universal set of gates to physically implement quantum computing and discusses initial steps toward spin-photon entanglement. Both are addressed through coherent control of the spin state in a magnetic field with optical pulses. This work experimentally demonstrates coherent rotations of the electron spin. First, the electron spin is rotated at up to 0.5 terahertz about the optical axis by a detuned picosecond optical pulse. The rotation occurs via a nearly resonant stimulated spin-flip Raman process involving a negatively charged exciton (trion). Second, rotation about an orthogonal axis is demonstrated due to electron spin precession about the magnetic field between two detuned optical pulses. The magnitude of the electron g factor is measured to be 0.4, and the rotation speed is 30 gigahertz in a 6.6 Tesla field. Geometric phases are detected in quantum dots for the first time due to cyclic Rabi oscillations driven by a resonant continuous-wave laser. These geometric phases provide another method of spin rotation and can be used in a gate. Any combination of these methods that provides spin rotation about two orthogonal axes can form an arbitrary rotation and together with a phase gate can form any unitary single qubit gate. Finally, this thesis also presents a detailed experimental procedure for creating a partial entanglement of internal variables within a quantum dot spin-exciton system, as a preliminary step to spin-photon entanglement. It has been proposed that entanglement between non-adjacent qubits in a large qubit network could occur via a photon, fueling research to demonstrate spin-photon entanglement. The experiment proposed here will create the precursor state in 25 picoseconds with a predicted fidelity of 0.985, and the precursor superposition state has a theoretical entropy of entanglement of 0.92.

•Jan 1, 2011•0 citations

Optically controlled single-qubit rotations in self-assembled InAs quantum dots

Clive Emary, Lu Jeu Sham

We present a theory of the optical control of the spin of an electron in an InAs quantum dot. We show how two Raman-detuned laser pulses can be used to obtain arbitrary single-qubit rotations via the excitation of an intermediate trion state. Our theory takes into account a finite in-plane hole g -factor and hole mixing. We show that such rotations can be performed to high fidelities with pulses lasting a few tens of picoseconds.

arXiv:cond-mat/0608518•Journal of Physics Condensed Matter•Jan 17, 2007•33 citations
We report coherent optical control of a biexciton (two electron-hole pairs), confined in a single quantum dot, that shows coherent oscillations similar to the excited-state Rabi flopping in an isolated atom. The pulse control of the biexciton dynamics, combined with previously demonstrated control of the single-exciton Rabi rotation, serves as the physical basis for a two-bit conditional quantum logic gate. The truth table of the gate shows the features of an all-optical quantum gate with interacting yet distinguishable excitons as qubits. Evaluation of the fidelity yields a value of 0.7 for the gate operation. Such experimental capability is essential to a scheme for scalable quantum computation by means of the optical control of spin qubits in dots.
Summary form only given. We use transient nonlinear optical spectroscopy to demonstrate Rabi oscillations between each of the dipole coupled states, corresponding to qubit rotations. The interface fluctuation GaAs quantum dots are probed with sub-micron spatial resolution. The resonant excitation of the biexciton requires a two-color scheme in a hyper Raman gain configuration. To demonstrate exciton Rabi oscillations, the laser wavelength is fixed at the exciton resonance. Exciton and biexciton Rabi oscillations correspond to qubit rotations of the |00> to |01> or |10> state and the |01> or |10> to |11> state respectively, depending on the polarization of the excitation field.
Optically driven self-assembled quantum dots are leading candidates for use in quantum computers because of their potential for high speed gate operations and relatively compact design. In this approach, each dot is charged with a single electron whose spin serves as the quantum bit (qubit). This thesis addresses the need for a universal set of gates to physically implement quantum computing and discusses initial steps toward spin-photon entanglement. Both are addressed through coherent control of the spin state in a magnetic field with optical pulses. This work experimentally demonstrates coherent rotations of the electron spin. First, the electron spin is rotated at up to 0.5 terahertz about the optical axis by a detuned picosecond optical pulse. The rotation occurs via a nearly resonant stimulated spin-flip Raman process involving a negatively charged exciton (trion). Second, rotation about an orthogonal axis is demonstrated due to electron spin precession about the magnetic field between two detuned optical pulses. The magnitude of the electron g factor is measured to be 0.4, and the rotation speed is 30 gigahertz in a 6.6 Tesla field. Geometric phases are detected in quantum dots for the first time due to cyclic Rabi oscillations driven by a resonant continuous-wave laser. These geometric phases provide another method of spin rotation and can be used in a gate. Any combination of these methods that provides spin rotation about two orthogonal axes can form an arbitrary rotation and together with a phase gate can form any unitary single qubit gate. Finally, this thesis also presents a detailed experimental procedure for creating a partial entanglement of internal variables within a quantum dot spin-exciton system, as a preliminary step to spin-photon entanglement. It has been proposed that entanglement between non-adjacent qubits in a large qubit network could occur via a photon, fueling research to demonstrate spin-photon entanglement. The experiment proposed here will create the precursor state in 25 picoseconds with a predicted fidelity of 0.985, and the precursor superposition state has a theoretical entropy of entanglement of 0.92.