arXiv subjects

Shi-fan Qi

Publications and source records attributed to Shi-fan Qi.

14 recordsLinked to original sources

arXiv2026

Remote magnon-phonon entanglement in the waveguide-magnomechanics

Generating long-distance quantum entanglement is crucial for advancing quantum information processing. In this work, we propose a protocol for generating remote magnon-phonon entanglement in a hybrid waveguide-magnomechanical system, where multiple spatially separated magnon modes couple to a common waveguide while interacting with their respective phonon modes. By applying tailored pulsed drives and engineering the magnomechanical interactions, our scheme enables the creation of diverse long-distance and dynamically stable entanglement. Beyond basic magnon-phonon two-mode entanglement, it supports genuine multimode entanglement between a single phonon and multiple magnons, bipartite entanglement between a single magnon and multiple phonons, as well as genuine four-mode entanglement involving two magnons and two phonons. Moreover, we show that dissipative magnon-magnon interactions mediated by traveling photons can generate substantially stronger remote entanglement than coherent couplings. Our work provides an experimentally feasible scheme for the remote generation of magnon-phonon entanglement.

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arXiv2026

Dynamical generation of stable optical-microwave squeezing in structured reservoirs

Two-mode squeezed states as paradigmatic entangled resources have broad applications in quantum information processing. Here, we study the generation of stable optical-microwave squeezing in structured environments within a hybrid electro-optomechanical system, where a mechanical oscillator is simultaneously coupled to an optical cavity mode and a microwave mode of an LC resonator. Specifically, an effective Hamiltonian that captures the optical-microwave squeezing interaction is constructed by combining strongly modulated driving fields applied to both photonic modes with a mechanical parametric amplifier. Based on this effective model, the dynamical evolution of two-mode squeezing in structured environments is analyzed. It is remarkably shown that the non-Markovian noise can substantially enhance the squeezing level in comparison to the Markovian case, and that two-mode squeezing can persist even in the absence of external driving fields under non-Markovian conditions, thereby mitigating the detrimental effects of anti-squeezing. Furthermore, the persistence of the two-mode squeezed state is enhanced when the environmental spectral densities of the microwave and optical modes are identical. Our work provides a theoretical framework for generating and persisting two-mode squeezing in structured environments.

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arXiv2026

General Theory of Stable Microwave-Optical Quantum Resources in Hybrid-System Dynamics

We develop a general theoretical framework for characterizing stable quantum resources between microwave and optical modes in the dynamics of multipartite hybrid quantum systems with intermediary modes. The effective Hamiltonian for microwave-optical (MO) squeezing is formulated via strong interactions in the microwave-intermediary-optical hybrid system, and based on which rigorous solutions for the dynamics of MO entanglement and quantum steering are derived analytically. Remarkably, it is found that stable MO quantum resources can survive in the unsteady evolution beyond the steady one, and the unsteady evolution can exhibit the enhanced quality over the limit of quantum resources in the steady-state case. Furthermore, the stable MO entanglement as well as one-way and two-way quantum steerings are efficiently controllable by modulating the effective coupling strength. The validity of our theory is demonstrated by applying it to the typical models of electro-optomechanical and cavity optomagnomechanical hybrid systems.

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arXiv2026

Dynamically stable two-mode squeezing in cavity optomechanics

Bosonic two-mode squeezed states are paradigmatic entangled states with broad applications in quantum information processing and quantum metrology. In this work, we propose a two-mode squeezing scheme in a hybrid three-mode cavity optomechanical system, where a mechanical resonator couples to two microwave (or optical) photon modes. By applying and modulating strong driving pulses to the photon modes, we construct an effective Hamiltonian that describes two-photon squeezing mediated by the mechanical mode. This effective Hamiltonian is validated through diagonalization of the full system's transition matrix in the Heisenberg picture. With the effective Hamiltonian, we provide a rigorous theoretical solution for the dynamical process of squeezing generation within the framework of open quantum system. Our analysis reveals that stable two-mode squeezing can be obtained by optimizing the squeezing quadrature operator, even in unsteady system states. Remarkably, the squeezing level can exceed the maximum achievable under system stability conditions. Furthermore, we show that our protocol is robust against systematic errors in both driving intensity and frequency, as well as against thermal Markovian noises. Our work provides an extendable approach for generating two-mode squeezed states between indirectly coupled Gaussian modes.

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arXiv2025

Kerr-magnon-assisted asymptotic stationary photon-phonon squeezing

Bosonic two-mode squeezed states are paradigmatic entangled states in continuous variable systems, which have broad applications in quantum information processing. In this work, we propose a photon-phonon squeezing protocol assisted by a Kerr magnon within a hybrid cavity magnomechanical system. We construct an effective Hamiltonian that accounts for photon-phonon squeezing through strong photon-magnon interaction and modulation over the driving on the photon mode. The effective Hamiltonian can be confirmed by the diagonalization of the system's Liouvillian superoperator. With the effective Hamiltonian and quantum Langevin equation, we provide a rigorous theoretical solution for the dynamical process of squeezing generation. Our finding indicates that the asymptotic stationary squeezing can be obtained by optimizing the squeezing quadrature operator, even when the covariance matrix of the system still varies with time. This squeezing level can exceed the maximum value under stable conditions. Moreover, our analysis reveals that a proper Kerr nonlinearity of the magnon can further promote the squeezing generation. Our work provides an extendable framework for generating squeezed states of two Gaussian modes with indirect coupling.

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arXiv2024

Quantum recharging by shortcut to adiabaticity

Quantum battery concerns about population redistribution and energy dispatch over controllable quantum systems. Under unitary transformation, ergotropy rather than energy plays an essential role in describing the accumulated useful work. Thus, the charging and recharging of quantum batteries are distinct from the electric-energy input and reuse of classical batteries. In this work, we focus on recharging a three-level quantum battery that has been exhausted under self-discharging and work extraction. We find that the quantum battery cannot be fully refreshed with the maximum ergotropy only by the driving pulses for unitary charging. For an efficient refreshment of the quantum battery, we propose a fast and stable recharging protocol based on postselection and shortcut to adiabaticity. More than accelerating the adiabatic passage for charging, the protocol can eliminate unextractable energy and is robust against driving errors and environmental decoherence. Our protocol is energy-saving and experimental-feasible, even in systems with the forbidden transition.

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arXiv2023

Generating entangled states from coherent states in circuit-QED

Entangled states are self-evidently important to a wide range of applications in quantum communication and quantum information processing. We propose an efficient and convenient two-step protocol for generating Bell states and NOON states of two microwave resonators from merely coherent states. In particular, we derive an effective Hamiltonian for resonators coupled to a superconducting $Λ$-type qutrit in the dispersive regime. By the excitation-number-dependent Stark shifts of the qutrit transition frequencies, we are able to individually control the amplitudes of specified Fock states of the resonators associated with relevant qutrit transition, using carefully tailored microwave drive signals. Thereby an arbitrary bipartite entangled state in Fock space can be generated by a typical evolution-and-measurement procedure. We analysis the undesired state transitions and the robustness of our protocol against the systematic errors from the microwave driving intensity and frequency, the quantum decoherence of all components, and the crosstalk of two resonators. In addition, we demonstrate that our protocol can be extended to a similar scenario with a $Ξ$-type qutrit.

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arXiv2023

Floquet generation of magnonic NOON state

We propose a concise and deterministic protocol to generate NOON states in a hybrid system consisting of a superconducting qubit, a circuit resonator mode, and two magnonic modes, based on Floquet engineering. In particular, we construct a time-reversal-symmetry broken Hamiltonian for chiral state propagation of the three continuous-variable modes depending on qubit state, by the time modulation over qubit-resonator interaction and magnon frequency. Then an arbitrary magnonic NOON state can be generated by a typical preparing-and-measurement procedure. We analyze the robustness of our protocol against the systematic errors in the qubit-magnon coupling strength, the Floquet-driving intensity, the frequency mismatch of the magnons, and the counter-rotating interactions. We can obtain a high-fidelity NOON state in the presence of the quantum dissipation on all components.

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arXiv2022

Chiral current in Floquet cavity-magnonics

Floquet engineering can induce complex collective behaviour and interesting synthetic gauge-field in quantum systems through temporal modulation of system parameters by periodic drives. Using a Floquet drive on frequencies of the magnon modes, we realize a chiral state-transfer in a cavity-magnonic system. The time-reversal symmetry is broken in such a promising platform for coherent information processing. In particular, the photon mode is adiabatically eliminated in the large-detuning regime and the magnon modes under conditional longitudinal drives can be indirectly coupled to each other with a phase-modulated interaction. The effective Hamiltonian is then used to generate chiral currents in a circular loop, whose dynamics is evaluated to measure the symmetry of the system Hamiltonian. Beyond the dynamics limited in the manifold with a fixed number of excitations, our protocol applies to the continuous-variable systems with arbitrary states. Also it is found to be robust against the systematic errors in the photon-magnon coupling strength and Kerr nonlinearity.

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arXiv2022

Accelerated adiabatic passage in cavity magnomechanics

Cavity magnomechanics provides a readily-controllable hybrid system, that consisted of cavity mode, magnon mode, and phonon mode, for quantum state manipulation. To implement a fast-and-robust state transfer between the hybrid photon-magnon mode and the phonon mode, we propose two accelerated adiabatic-passage protocols individually based on the counterdiabatic Hamiltonian for transitionless quantum driving and the Levis-Riesenfeld invariant for inverse engineering. Both the counterdiabatic Hamiltonian and the Levis-Riesenfeld invariant generally apply to the continuous-variable systems with arbitrary target states. It is interesting to find that our counterdiabatic Hamiltonian can be constructed in terms of the creation and annihilation operators rather than the system-eigenstates and their time-derivatives. Our protocol can be optimized with respect to the stability against the systematic errors of coupling strength and frequency detuning. It contributes to a quantum memory for photonic and magnonic quantum information. We also discuss the effects from dissipation and the counter-rotating interactions.

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arXiv2021

Generation of Bell and GHZ states from a hybrid qubit-photon-magnon system

We propose a level-resolved protocol in a hybrid architecture for connecting a superconducting qubit and a magnon mode contained within a microwave cavity (resonator) to generate the local and global entangled states, enabling a wide range of applications in quantum communication, quantum metrology, and quantum information processing. Exploiting the high-degree of controllability in such a hybrid qubit-photon-magnon system, we derive effective Hamiltonians at the second- or the third-order resonant points by virtue of the strong counter-rotating interactions between the resonator and the qubit and between the resonator and the magnon. Consequently, we can efficiently generate the Bell states of the photon-magnon and the qubit-magnon subsystems and the Greenberger-Horne-Zeilinger state of the whole hybrid system. We also check the robustness of our protocol against the environmental noise by the Lindblad master equation. Our work makes this hybrid platform of high-degree of controllability a high-fidelity candidate for the realization of the maximally-entangled multiple states.

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arXiv2021

Magnon-mediated quantum battery under systematic errors

Quantum battery is one of the most prominent micro-devices in the rapid-developing quantum thermodynamics. We propose a quantum charging protocol in which both battery and charger are consisted of a many-spin system. The battery and charger are connected via the Kittle mode of the magnon system, that serves as a charging wire and then enables a long-range charging protocol. Counter-intuitively, we find that the spin-spin couplings insider both battery and charger can be used to promote the charging performance in comparison to the noninteracting condition. And a remarkable promotion is realized at a "sweet" spot in terms of the average coupling strength. Moreover, we apply the quantum-state-diffusion equation to test the robustness of our magnon-mediated charging protocol to the systematic errors about the magnon frequency.

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arXiv2021

Magnon-assisted photon-phonon conversion in the presence of the structured environments

Quantum conversion or interface is one of the most prominent protocols in quantum information processing and quantum state engineering. We propose a photon-phonon conversion protocol in a hybrid magnomechanical system comprising a microwave optical mode, a driven magnon mode and a mechanical-vibrating mode. The microwave photons in the optical cavity are coupled to the magnons by the magnetic-dipole interaction, and the latter are coupled to the mechanical phonons by the magnetostrictive interaction. With strong photon-magnon interaction and strong driving on magnon, an effective Hamiltonian is constructed to describe the conversion between photons and phonons nearby their resonant point. The cavity-magnon system can then play the role of a quantum memory. Moreover, the faithfulness of the photon-phonon conversion is estimated in terms of fidelities for state evolution and state-independent transfer. The former is discussed in the Lindblad master equation taking account the leakages of photon, phonon and magnon into consideration. The latter is derived by the Heisenberg-Langevin equation considering the non-Markovian noise from the structured environments for both optical and mechanical modes. The state-evolution fidelity is found to be robust to the weak leakage. The transfer fidelity can be maintained by the Ohmic and sub-Ohmic environments of the photons and is insensitive to the $1/f$ noise of the phonons. Our work thus provides an interesting application for the magnon system as a photon-phonon converter in the microwave regime.

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arXiv2019

Generating NOON states in circuit QED using multi-photon resonance in the presence of counter-rotating interactions

The NOON states are valuable quantum resources, which have a wide range of applications in quantum communication, quantum metrology, and quantum information processing. Here we propose a fast, concise and reliable protocol for deterministically generating the NOON states of two resonators coupled to a single $\triangle$-type superconducting qutrit. In particular, we derive the effective Hamiltonians at the multi-photon resonances by virtue of the strong counter-rotating interaction between the resonator modes and the qutrit. Based on these crucial effective Hamiltonians, our protocol simplifies the previous ones using the single-photon resonance and consequently reduces the number of operations for state preparation. To test the robustness of this protocol, we analyze the effects from both the decoherence including dissipation and dephasing and the crosstalk of resonator modes on the state fidelity through a Lindblad master equation in the eigenstates of the full Hamiltonian.

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