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

Physical Review A

Entangled particles in a dynamically controlled trap

Thomas Häberle, Matthias Freyberger

Published May 29, 2014• 5 citations
Publisher

Abstract

We control the entanglement of motion between two colliding particles by dynamically varying the frequency of their common trap. In particular, we restrict the possible frequencies to a narrow interval and limit the average energy of the particles to a maximal value. In order to solve this restricted optimization problem we propose a modified gradient method. It turns out that the motional entanglement generated by collisions can be considerably improved.

DOI
10.1103/physreva.89.052332

Related papers

Quantum optimal control of the dissipative production of a maximally entangled state

Karl P. Horn, Florentin Reiter, Yiheng Lin +2 more

Entanglement generation can be robust against certain types of noise in approaches that deliberately incorporate dissipation into the system dynamics. The presence of additional dissipation channels may, however, limit fidelity and speed of the process. Here we show how quantum optimal control techniques can be used to both speed up the entanglement generation and increase the fidelity in a realistic setup, whilst respecting typical experimental limitations. For the example of entangling two trapped ion qubits (Lin et al 2013 Nature 504 415), we find an improved fidelity by simply optimizing the polarization of the laser beams utilized in the experiment. More significantly, an alternate combination of transitions between internal states of the ions, when combined with optimized polarization, enables faster entanglement and decreases the error by an order of magnitude.

arXiv:1807.10052•New Journal of Physics•Nov 23, 2018•36 citations

Nonequilibrium entanglement between levitated masses under optimal control

Alexander N. Poddubny, Klemens Winkler, Benjamin A. Stickler +3 more

We present a protocol that maximizes unconditional entanglement generation between two masses interacting directly through $1/r^{n}$ potential. The protocol combines optimal quantum control of continuously measured masses with their non-equilibrium dynamics, driven by a time-dependent interaction strength. Applied to a pair of optically trapped sub-micron particles coupled via electrostatic interaction, our protocol enables unconditional entanglement generation at the fundamental limit of the conditional state and with an order of magnitude smaller interaction between the masses compared to the existing steady-state approaches.

arXiv:2408.06251•Aug 12, 2024•0 citations

Entangling two levitated particles in free space via trap modulation and Bayesian feedback

Jinke Cao, Qi Guo, Huatang Tan

We propose an optimal control scheme for generating quantum entanglement between two optically-levitated nanoparticles in free space. Specifically, we consider that the mechanical motion frequencies of the two levitated particles are modulated by adjusting the amplitude of the trapping beam. The two particles are coupled through Coulomb interaction, and the particles' positions are continuously monitored via homodyne detection on the back-scattered light from both particles. By employing an optimal Bayesian feedback scheme, we achieve unconditional entanglement between the two particles in steady states. More precisely, a Kalman filter is used to estimate the states of the two particles and subsequently a linear quadratic regulator is applied to derive the optimal feedback forces exerted on the particles. Physically, periodic modulation enables significant quantum squeezing in both the common mode and the differential mode of the two particles. The Coulomb coupling between the particles introduces a difference in the squeezing of the two normal modes, thereby facilitating the entanglement of the two levitated particles. Our scheme allows for the realization of both conditional and unconditional entanglement at relatively low measurement efficiencies and with low requirements for Coulomb coupling strength, significantly enhancing the feasibility of implementation.

arXiv:2505.12865•May 19, 2025•0 citations

All-optical generation of quantum entangled states with strictly constrained ultrafast laser pulses

Yu Guo, Xiaobing Luo, Shan Ma +1 more

We present a quantum optimal control theory study combined with theoretical analysis to determine a pulsed laser field, capable of generating a maximally entangled state in two trapped two-level atoms. By expanding the time-dependent unitary operator to the first leading term of Magnus expansion, we reexamine the pulse area theorem for the trapped atoms driven by an arbitrarily temporary field. Due to the dipole-dipole interaction blockade, we find that the two trapped atoms described by a three-level ladder system can be reduced into an equivalent two-level model by using narrow-bandwidth pulses, leading to an analytical solution for generating the maximally entangled state. We also solve a highly constrained optimization problem to search for optimal laser pulses with broad bandwidths. A zero pulse-area constraint is employed to remove the dc offset of the optimized laser pulses, and a fixed fluence limitation combined with a constant pulse-area constraint at the resonant frequency of the equivalent two-level system are utilized to restrict the unitary evolution of quantum systems by the first leading term of Magnus expansion. This work provides a potentially useful approach to find all-optical control schemes for generating the maximally entangled state by using ultrafast laser pulses while satisfying multiple strict limitations.

Physical Review A•Aug 12, 2019•27 citations

Entanglement of Atoms via Cold Controlled Collisions

Dieter Jaksch, Hans J. Briegel, J. I. Cirac +2 more

We show that by using cold controlled collisions between two atoms one can achieve conditional dynamics in moving trap potentials. We discuss implementing two qubit quantum gates and efficient creation of highly entangled states of many atoms in optical lattices.

arXiv:quant-ph/9810087•Physical Review Letters•Mar 1, 1999•795 citations

Maximizing optomechanical entanglement with optimal control

Dionisis Stefanatos

In this article, we formulate the generation of optomechanical entanglement between the linearly coupled cavity field and the mechanical resonator as an optimal control problem in hyperbolic space $H^3$, with control input the coupling rate of the two oscillators. Next, we use optimal control theory to find the allowed optimal values of the coupling which maximize the amount of generated entanglement for a fixed duration of the interaction. Finally, we employ a numerical optimization method to obtain the exact optimal pulse sequences for several illustrative examples. In the strong coupling regime, where the coupling rate is comparable or larger than the frequency of the mechanical resonator, a substantial amount of entanglement can be generated within a fraction of a single oscillator period.

arXiv:1612.05144•Dec 15, 2016•0 citations
We control the entanglement of motion between two colliding particles by dynamically varying the frequency of their common trap. In particular, we restrict the possible frequencies to a narrow interval and limit the average energy of the particles to a maximal value. In order to solve this restricted optimization problem we propose a modified gradient method. It turns out that the motional entanglement generated by collisions can be considerably improved.
Entanglement generation can be robust against certain types of noise in approaches that deliberately incorporate dissipation into the system dynamics. The presence of additional dissipation channels may, however, limit fidelity and speed of the process. Here we show how quantum optimal control techniques can be used to both speed up the entanglement generation and increase the fidelity in a realistic setup, whilst respecting typical experimental limitations. For the example of entangling two trapped ion qubits (Lin et al 2013 Nature 504 415), we find an improved fidelity by simply optimizing the polarization of the laser beams utilized in the experiment. More significantly, an alternate combination of transitions between internal states of the ions, when combined with optimized polarization, enables faster entanglement and decreases the error by an order of magnitude.
We present a protocol that maximizes unconditional entanglement generation between two masses interacting directly through 1/rn1/r^{n}1/rn potential. The protocol combines optimal quantum control of continuously measured masses with their non-equilibrium dynamics, driven by a time-dependent interaction strength. Applied to a pair of optically trapped sub-micron particles coupled via electrostatic interaction, our protocol enables unconditional entanglement generation at the fundamental limit of the conditional state and with an order of magnitude smaller interaction between the masses compared to the existing steady-state approaches.
We propose an optimal control scheme for generating quantum entanglement between two optically-levitated nanoparticles in free space. Specifically, we consider that the mechanical motion frequencies of the two levitated particles are modulated by adjusting the amplitude of the trapping beam. The two particles are coupled through Coulomb interaction, and the particles' positions are continuously monitored via homodyne detection on the back-scattered light from both particles. By employing an optimal Bayesian feedback scheme, we achieve unconditional entanglement between the two particles in steady states. More precisely, a Kalman filter is used to estimate the states of the two particles and subsequently a linear quadratic regulator is applied to derive the optimal feedback forces exerted on the particles. Physically, periodic modulation enables significant quantum squeezing in both the common mode and the differential mode of the two particles. The Coulomb coupling between the particles introduces a difference in the squeezing of the two normal modes, thereby facilitating the entanglement of the two levitated particles. Our scheme allows for the realization of both conditional and unconditional entanglement at relatively low measurement efficiencies and with low requirements for Coulomb coupling strength, significantly enhancing the feasibility of implementation.
We present a quantum optimal control theory study combined with theoretical analysis to determine a pulsed laser field, capable of generating a maximally entangled state in two trapped two-level atoms. By expanding the time-dependent unitary operator to the first leading term of Magnus expansion, we reexamine the pulse area theorem for the trapped atoms driven by an arbitrarily temporary field. Due to the dipole-dipole interaction blockade, we find that the two trapped atoms described by a three-level ladder system can be reduced into an equivalent two-level model by using narrow-bandwidth pulses, leading to an analytical solution for generating the maximally entangled state. We also solve a highly constrained optimization problem to search for optimal laser pulses with broad bandwidths. A zero pulse-area constraint is employed to remove the dc offset of the optimized laser pulses, and a fixed fluence limitation combined with a constant pulse-area constraint at the resonant frequency of the equivalent two-level system are utilized to restrict the unitary evolution of quantum systems by the first leading term of Magnus expansion. This work provides a potentially useful approach to find all-optical control schemes for generating the maximally entangled state by using ultrafast laser pulses while satisfying multiple strict limitations.
In this article, we formulate the generation of optomechanical entanglement between the linearly coupled cavity field and the mechanical resonator as an optimal control problem in hyperbolic space H3H^3H3, with control input the coupling rate of the two oscillators. Next, we use optimal control theory to find the allowed optimal values of the coupling which maximize the amount of generated entanglement for a fixed duration of the interaction. Finally, we employ a numerical optimization method to obtain the exact optimal pulse sequences for several illustrative examples. In the strong coupling regime, where the coupling rate is comparable or larger than the frequency of the mechanical resonator, a substantial amount of entanglement can be generated within a fraction of a single oscillator period.