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

Journal of Physics Conference Series

Optimized dynamics of state to state transitions in 2-electron quantum dot molecules

L. Sælen, Raymond Nepstad, Ilan Degani, J. P. Hansen

Published Nov 1, 2009• 0 citations
Publisher

Abstract

We investigate optimal control strategies for state to state transitions in a model of a quantum dot molecule containing two active strongly interacting electrons. The resulting optimized electric pulses are in the THz regime and can populate combinations of states with very short transition times. The speedup compared to intuitively constructed pulses is an order of magnitude. We furthermore make use of optimized pulse control in the simulation of an experimental preparation of the molecular quantum dot system. It is shown that exclusive population of certain excited states leads to a complete suppression of spin dephasing, as predicted in Nepstad et al. [1].

DOI
10.1088/1742-6596/194/15/152006

Related papers

Optimal control strategies for coupled quantum dots

E. Räsänen, A. Putaja, Yousof Mardoukhi

Abstract Semiconductor quantum dots are ideal candidates for quantum information applications in solid-state technology. However, advanced theoretical and experimental tools are required to coherently control, for example, the electronic charge in these systems. Here we demonstrate how quantum optimal control theory provides a powerful way to manipulate the electronic structure of coupled quantum dots with an extremely high fidelity. As alternative control fields we apply both laser pulses as well as electric gates, respectively. We focus on double and triple quantum dots containing a single electron or two electrons interacting via Coulomb repulsion. In the two-electron situation we also briefly demonstrate the challenges of timedependent density-functional theory within the adiabatic local-density approximation to produce comparable results with the numerically exact approach.

Open Physics•Jan 1, 2013•6 citations

Fast optical control of a coded qubit in a triple quantum dot

Diego S Acosta Coden, Sergio S Gomez, Rodolfo H Romero +2 more

Abstract In this work, we study strategies for the optical control, within the dipole approximation, of a qubit encoded in the total intrinsic angular momentum states of three electrons confined in a triple quantum dot. The system is modeled using effective confining potentials, and its electronic structure is calculated using the configuration interaction method. Optimal control theory (OCT) was applied to design low-fluence time-dependent electric fields controlling the qubit in times shorter than a nanosecond. The resulting pulses produce transitions between the qubit states for experimentally available field amplitudes with high fidelity. Moreover, studying the dominant frequencies present in the OCT pulses, we show that the switching between the qubit states can also be achieved with simpler combinations of sinusoidal driving fields that produce transitions to intermediate states. The limitations of an extended Hubbard description for the model and its dynamic behavior are also discussed.

arXiv:1807.02006•Physica Scripta•Dec 10, 2018•2 citations

Shaped electric fields for fast optimal manipulation of electron spin and position in a double quantum dot

J. A. Budagosky, D. V. Khomitsky, Eugene Ya. Sherman +1 more

We use quantum optimal control theory algorithms to design external electric fields that drive the coupled spin and orbital dynamics of an electron in a double quantum dot, subject to the spin-orbit coupling and Zeeman magnetic fields. We obtain time profiles of multifrequency electric field pulses which increase the rate of spin-flip transitions by several orders of magnitude in comparison with monochromatic fields, where the spin Rabi oscillations were predicted to be very slow. This precise (with fidelity higher than $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$) and fast (at the time scale of the order of 0.1 ns, comparable with the Zeeman spin rotation and the interdot tunneling time) simultaneous control of the spin and position is achieved while keeping the electron in the four lowest tunneling- and Zeeman-split levels through the duration of the pulse. The proposed algorithms suggest effective applications in spintronics and quantum information devices.

arXiv:1510.04502•Physical review. B./Physical review. B•Jan 14, 2016•5 citations

Fast optical control of a coded qubit in a triple quantum dot

Diego S Acosta Coden, Sergio S. Gómez, Rodolfo H. Romero +2 more

In this work, we study strategies for the optical control, within the dipole approximation, of a qubit encoded in the total intrinsic angular momentum states of three electrons confined in a triple quantum dot. The system is modeled using effective confining potentials, and its electronic structure is calculated using the configuration interaction method. Optimal control theory (OCT) was applied to design low-fluence time-dependent electric fields controlling the qubit in times shorter than a nanosecond. The resulting pulses produce transitions between the qubit states for experimentally available field amplitudes with high fidelity. Moreover, studying the dominant frequencies present in the OCT pulses, we show that the switching between the qubit states can also be achieved with simpler combinations of sinusoidal driving fields that produce transitions to intermediate states. The limitations of an extended Hubbard description for the model and its dynamic behavior are also discussed.

•Feb 1, 2019•2 citations

Ultra-slow orbital and spin dynamics in an electrically tunable quantum dot molecule

Christopher Thalacker, Michelle Lienhart, Markus Stöcker +13 more

Tunnel-coupled optically active quantum dot molecules (QDMs), have the potential to operate as spin-photon-interfaces with coupled spins that interact with two different photon frequencies at the same time. A prerequisite is to deterministically prepare two (electron or hole) spins in the QDM and be able to electrically tune the orbital state couplings. Here, we demonstrate the sequential optical charging of a single QDM with two electron spins while simultaneously maintaining the ability to widely tune orbital couplings using static electric fields and optically drive the system for quantum light generation. We optically prepare one- and two-spin states, initialize via optical pumping and explore orbital and spin relaxation dynamics for one and two-spin states as a function of the energy detuning and hybridization of orbital states. For two-spin states, remarkably long S-T relaxation times are observed extending beyond $\sim 100μs$ with strong dependence on the relative energy of ground and excited two-spin states. Qualitative agreement is observed with $\mathbf{k \cdot p}$ calculations of phonon-mediated spin-relaxation. Our results provide new quantitative understanding of the dynamics of one and two-spin states and confirm their suitability of QDMs for creating multidimensional photonic cluster states by exploiting tunable spin-spin exchange couplings at zero magnetic fields combined with optical driving.

cond-mat.mes-hallCross-listedarXiv:2603.05610•Mar 9, 2026

Complete All-Optical Quantum Control of Electron Spins in InAs/GaAs Quantum Dot Molecule

Guy Cohen

The spin states of electrons and holes confined in InAs quantum dot molecules have recently come to fore as a promising system for the storage or manipulation of quantum information. We describe here a feasible scheme for complete quantum optical control of two electron spin qubits in two vertically-stacked singly-charged InAs quantum dots coupled by coherent electron tunneling. With an applied magnetic field transverse to the growth direction, we construct a universal set of gates that corresponds to the possible Raman transitions between the spin states. We detail the procedure to decompose a given two-qubit unitary operation, so as to realize it with a successive application of up to 8 of these gates. We give the pulse shapes for the laser pulses used to implement this universal set of gates and demonstrate the realization of the two-qubit quantum Fourier transform with fidelity of 0.881 and duration of 414 ps. Our proposal therefore offers an accessible path to universal computation in quantum dot molecules and points to the advantages of using pulse shaping incoherent manipulation of optically active quantum dots to mitigate the negative effects of unintended dynamics and spontaneous emission.

arXiv:1501.01952•Jan 8, 2015•1 citation
We investigate optimal control strategies for state to state transitions in a model of a quantum dot molecule containing two active strongly interacting electrons. The resulting optimized electric pulses are in the THz regime and can populate combinations of states with very short transition times. The speedup compared to intuitively constructed pulses is an order of magnitude. We furthermore make use of optimized pulse control in the simulation of an experimental preparation of the molecular quantum dot system. It is shown that exclusive population of certain excited states leads to a complete suppression of spin dephasing, as predicted in Nepstad et al. [1].
Abstract Semiconductor quantum dots are ideal candidates for quantum information applications in solid-state technology. However, advanced theoretical and experimental tools are required to coherently control, for example, the electronic charge in these systems. Here we demonstrate how quantum optimal control theory provides a powerful way to manipulate the electronic structure of coupled quantum dots with an extremely high fidelity. As alternative control fields we apply both laser pulses as well as electric gates, respectively. We focus on double and triple quantum dots containing a single electron or two electrons interacting via Coulomb repulsion. In the two-electron situation we also briefly demonstrate the challenges of timedependent density-functional theory within the adiabatic local-density approximation to produce comparable results with the numerically exact approach.
Abstract In this work, we study strategies for the optical control, within the dipole approximation, of a qubit encoded in the total intrinsic angular momentum states of three electrons confined in a triple quantum dot. The system is modeled using effective confining potentials, and its electronic structure is calculated using the configuration interaction method. Optimal control theory (OCT) was applied to design low-fluence time-dependent electric fields controlling the qubit in times shorter than a nanosecond. The resulting pulses produce transitions between the qubit states for experimentally available field amplitudes with high fidelity. Moreover, studying the dominant frequencies present in the OCT pulses, we show that the switching between the qubit states can also be achieved with simpler combinations of sinusoidal driving fields that produce transitions to intermediate states. The limitations of an extended Hubbard description for the model and its dynamic behavior are also discussed.
We use quantum optimal control theory algorithms to design external electric fields that drive the coupled spin and orbital dynamics of an electron in a double quantum dot, subject to the spin-orbit coupling and Zeeman magnetic fields. We obtain time profiles of multifrequency electric field pulses which increase the rate of spin-flip transitions by several orders of magnitude in comparison with monochromatic fields, where the spin Rabi oscillations were predicted to be very slow. This precise (with fidelity higher than $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$) and fast (at the time scale of the order of 0.1 ns, comparable with the Zeeman spin rotation and the interdot tunneling time) simultaneous control of the spin and position is achieved while keeping the electron in the four lowest tunneling- and Zeeman-split levels through the duration of the pulse. The proposed algorithms suggest effective applications in spintronics and quantum information devices.
In this work, we study strategies for the optical control, within the dipole approximation, of a qubit encoded in the total intrinsic angular momentum states of three electrons confined in a triple quantum dot. The system is modeled using effective confining potentials, and its electronic structure is calculated using the configuration interaction method. Optimal control theory (OCT) was applied to design low-fluence time-dependent electric fields controlling the qubit in times shorter than a nanosecond. The resulting pulses produce transitions between the qubit states for experimentally available field amplitudes with high fidelity. Moreover, studying the dominant frequencies present in the OCT pulses, we show that the switching between the qubit states can also be achieved with simpler combinations of sinusoidal driving fields that produce transitions to intermediate states. The limitations of an extended Hubbard description for the model and its dynamic behavior are also discussed.
Tunnel-coupled optically active quantum dot molecules (QDMs), have the potential to operate as spin-photon-interfaces with coupled spins that interact with two different photon frequencies at the same time. A prerequisite is to deterministically prepare two (electron or hole) spins in the QDM and be able to electrically tune the orbital state couplings. Here, we demonstrate the sequential optical charging of a single QDM with two electron spins while simultaneously maintaining the ability to widely tune orbital couplings using static electric fields and optically drive the system for quantum light generation. We optically prepare one- and two-spin states, initialize via optical pumping and explore orbital and spin relaxation dynamics for one and two-spin states as a function of the energy detuning and hybridization of orbital states. For two-spin states, remarkably long S-T relaxation times are observed extending beyond ∼100μs\sim 100μs∼100μs with strong dependence on the relative energy of ground and excited two-spin states. Qualitative agreement is observed with k⋅p\mathbf{k \cdot p}k⋅p calculations of phonon-mediated spin-relaxation. Our results provide new quantitative understanding of the dynamics of one and two-spin states and confirm their suitability of QDMs for creating multidimensional photonic cluster states by exploiting tunable spin-spin exchange couplings at zero magnetic fields combined with optical driving.
The spin states of electrons and holes confined in InAs quantum dot molecules have recently come to fore as a promising system for the storage or manipulation of quantum information. We describe here a feasible scheme for complete quantum optical control of two electron spin qubits in two vertically-stacked singly-charged InAs quantum dots coupled by coherent electron tunneling. With an applied magnetic field transverse to the growth direction, we construct a universal set of gates that corresponds to the possible Raman transitions between the spin states. We detail the procedure to decompose a given two-qubit unitary operation, so as to realize it with a successive application of up to 8 of these gates. We give the pulse shapes for the laser pulses used to implement this universal set of gates and demonstrate the realization of the two-qubit quantum Fourier transform with fidelity of 0.881 and duration of 414 ps. Our proposal therefore offers an accessible path to universal computation in quantum dot molecules and points to the advantages of using pulse shaping incoherent manipulation of optically active quantum dots to mitigate the negative effects of unintended dynamics and spontaneous emission.