Creation of high-dimensional entanglement of polar molecules via optimal control fields

Zhang, Zuo-Yuan; Liu, Jin-Ming

doi:10.1103/physreva.105.023113

Cited by 8 publications

(7 citation statements)

References 59 publications

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“…In our previous study, we have utilized OCT to implement entangled states and quantum gates in the polar molecular system. − In those studies, the molecule spacing is reluctantly set to values far less than the ones achieved under the current experimental technique. Moreover, to further reduce the computation costs while achieving high fidelity, refs , and take the SrO molecules with large electric dipole moments (nearly 9 D) as candidate qubits. However, the cooling and trapping of SrO molecules have not yet been experimentally reported yet.…”

Section: Discussionmentioning

confidence: 99%

“…The Hamiltonian of an ultracold polar molecule interacting with an external electric field can be written as , H i = B J 2 − μ i · ϵ i = B J 2 − μ i ϵ i cos nobreak0em0.25em⁡ θ Here, B is the rotational constant of the polar molecule, while J represents the angular momentum operator. Moreover, μ i denotes the molecular permanent dipole moment, and ϵ i denotes a static electric field interacting with the molecule, whereas θ is the angle between μ i and ϵ i .…”

Section: Theorymentioning

confidence: 99%

“…In dipole-coupled molecular arrays, it is necessary to take into account the dipole–dipole interactions, which can be written as the following form , V i , j = μ i · μ j − 3 ( bold-italicμ i · n ) · ( bold-italicμ boldj · n ) | r i − r j | 3 Here, r i ( j ) denotes the position vector of the i ( j )th molecule, and n represents a unit vector along r i , j with r i , j = r j – r i . In addition, following refs and , the vector r i , j is assumed to be orthogonal to the static electric field in the rest of this paper. Consequently, for N dipole–dipole-coupled ultracold polar molecules in an electric field, the whole systemic Hamiltonian reads H = ∑ i = 1 N H i + ∑ i = 1 N − 1 ∑ j = i + 1 N V i , j …”

Section: Theorymentioning

confidence: 99%

“…In addition, following refs and , the vector r i , j is assumed to be orthogonal to the static electric field in the rest of this paper. Consequently, for N dipole–dipole-coupled ultracold polar molecules in an electric field, the whole systemic Hamiltonian reads H = ∑ i = 1 N H i + ∑ i = 1 N − 1 ∑ j = i + 1 N V i , j …”

Section: Theorymentioning

confidence: 99%

“…Field. The Hamiltonian of an ultracold polar molecule interacting with an external electric field can be written as 20,65 H B B J J cos…”

Section: Polar Molecules In An Electricmentioning

confidence: 99%

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Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Zhang,

Sun,

Duan

et al. 2024

J. Chem. Theory Comput.

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Polar molecules are a promising platform for achieving scalable quantum information processing because of their long-range electric dipole–dipole interactions. Here, we take the coupled ultracold CaF molecules in an external electric field with gradient as qubits and concentrate on the creation of intermolecular entanglement with the method of deep reinforcement learning (RL). After sufficient training episodes, the educated RL agents can discover optimal time-dependent control fields that steer the molecular systems from separate states to two-qubit and three-qubit entangled states with high fidelities. We analyze the fidelities and the negativities (characterizing entanglement) of the generated states as a function of training episodes. Moreover, we present the population dynamics of the molecular systems under the influence of control fields discovered by the agents. Compared with the schemes for creating molecular entangled states based on optimal control theory, some conditions (e.g., molecular spacing and electric field gradient) adopted in this work are more feasible in the experiment. Our results demonstrate the potential of machine learning to effectively solve quantum control problems in polar molecular systems.

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Section: Discussionmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

“…Field. The Hamiltonian of an ultracold polar molecule interacting with an external electric field can be written as 20,65 H B B J J cos…”

Section: Polar Molecules In An Electricmentioning

confidence: 99%

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Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Zhang,

Sun,

Duan

et al. 2024

J. Chem. Theory Comput.

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Simulation of Grover Search with Polar CH₃CN Molecules by Optimal Control Fields

Zhang

Sun

et al. 2023

Adv Quantum Tech

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Theoretical schemes for the implementation of the Grover search algorithm are proposed based on ultracold polar molecules in an electric field. The molecular qubits and qudit are chosen as the field‐dressed states formed by the rotational modes of CH3CN. With the help of multi‐target optimal control theory, the microwave pulses for the elementary logic operations including the one‐qubit Hadamard gates and the conditional phase gates in a dipole‐dipole system are designed and the factorized Grover algorithm demonstrated using two coupled CH3CN molecules. To reduce the accumulation of imprecision and decoherence resulting from the combination of multiple elementary gates, the optimal pulses that can achieve the two‐qubit Hadamard gate and diffusion operation in one step are designed successfully. In this way, the probabilities to find the states corresponding to the desired elements in an unsorted database are enhanced to some extent. Moreover, the optimal pulse sequence suitable for a four‐level molecular qudit, which can be used to simulate the quantum search on a single CH3CN molecule with high fidelity, is designed. These results can shed some light on the physical realization of quantum computing based on ultracold polyatomic molecules.

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Simulation of quantum walks on a circle with polar molecules via optimal control

Ding,

Zhang,

Liu

2023

The Journal of Chemical Physics

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Quantum walks are the quantum counterpart of classical random walks and have various applications in quantum information science. Polar molecules have rich internal energy structure and long coherence time and thus are considered as a promising candidate for quantum information processing. In this paper, we propose a theoretical scheme for implementing discrete-time quantum walks on a circle with dipole–dipole coupled SrO molecules. The states of the walker and the coin are encoded in the pendular states of polar molecules induced by an external electric field. We design the optimal microwave pulses for implementing quantum walks on a four-node circle and a three-node circle by multi-target optimal control theory. To reduce the accumulation of decoherence and improve the fidelity, we successfully realize a step of quantum walk with only one optimal pulse. Moreover, we also encode the walker into a three-level molecular qutrit and a four-level molecular ququart and design the corresponding optimal pulses for quantum walks, which can reduce the number of molecules used. It is found that all the quantum walks on a circle in our scheme can be achieved via optimal control fields with high fidelities. Our results could shed some light on the implementation of discrete-time quantum walks and high-dimensional quantum information processing with polar molecules.

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Creation of high-dimensional entanglement of polar molecules via optimal control fields

Cited by 8 publications

References 59 publications

Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Simulation of Grover Search with Polar CH₃CN Molecules by Optimal Control Fields

Simulation of quantum walks on a circle with polar molecules via optimal control

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Creation of high-dimensional entanglement of polar molecules via optimal control fields

Cited by 8 publications

References 59 publications

Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Entanglement Generation of Polar Molecules via Deep Reinforcement Learning

Simulation of Grover Search with Polar CH3CN Molecules by Optimal Control Fields

Simulation of quantum walks on a circle with polar molecules via optimal control

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Simulation of Grover Search with Polar CH₃CN Molecules by Optimal Control Fields