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arXiv:2203.09247 · Advanced Quantum Technologies

Generation and Structuring of Multipartite Entanglement in a Josephson Parametric System

Kirill Viktorovich Petrovnin, Michael Romanovich Perelshtein, Tero Korkalainen, Visa Vesterinen, Ilari Lilja, Gheorghe Sorin Paraoanu, Pertti Juhani Hakonen

Published Oct 17, 2022• 13 citations
arXivHTMLPDF

Abstract

Abstract Quantum correlations are a vital resource in advanced information processing based on quantum phenomena. Remarkably, the vacuum state of a quantum field may act as a key element for the generation of multipartite quantum entanglement. In this work, generation of genuine tripartite entangled state and its control is achieved by the use of the phase difference between two continuous pump tones. Control of the subspaces of the covariance matrix for tripartite bisqueezed state is demonstrated. Furthermore, by optimizing the phase relationships in a three‐tone pumping scheme genuine quadripartite entanglement of a generalized H‐graph state (‐graph) is explored. This scheme provides a comprehensive control toolbox for the entanglement structure and allows to demonstrate, for first time to the authors' knowledge, genuine quadripartite entanglement of microwave modes. All experimental results are verified with numerical simulations of the nonlinear quantum Langevin equation. It is envisioned that quantum resources facilitated by multi‐pump configurations offer enhanced prospects for quantum data processing using parametric microwave cavities.

DOI
10.1002/qute.202200031

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Abstract Quantum correlations are a vital resource in advanced information processing based on quantum phenomena. Remarkably, the vacuum state of a quantum field may act as a key element for the generation of multipartite quantum entanglement. In this work, generation of genuine tripartite entangled state and its control is achieved by the use of the phase difference between two continuous pump tones. Control of the subspaces of the covariance matrix for tripartite bisqueezed state is demonstrated. Furthermore, by optimizing the phase relationships in a three‐tone pumping scheme genuine quadripartite entanglement of a generalized H‐graph state (‐graph) is explored. This scheme provides a comprehensive control toolbox for the entanglement structure and allows to demonstrate, for first time to the authors' knowledge, genuine quadripartite entanglement of microwave modes. All experimental results are verified with numerical simulations of the nonlinear quantum Langevin equation. It is envisioned that quantum resources facilitated by multi‐pump configurations offer enhanced prospects for quantum data processing using parametric microwave cavities.
Quantum information theory studies how quantum mechanics can be used to solve information processing tasks. The explotation of quantum mechanical properties can lead to quantum information protocols being more efficient than their classical counterparts. Continuous-Variable states offer an attractive platform for implementing various quantum information continuous variable protocols. In this thesis we show how Josephson Parametric Oscillators (JPO) can be used to generate multipartite entangled CV states for the use as a quantum resource in quantum information protocols. By simultaneously driving the JPO with two different pump tones, a tripartite entangled state is generated. The entanglement properties of the tripartite state are entirely contained in its 6-by-6 covariance matrix. Various entanglement measures are applied to the covariance matrix to demonstrate that the generated state exhibits genuine tripartite entanglement.
Quantum correlations are an essential resource in advanced information processing based on quantum phenomena. Remarkably, the vacuum state of a quantum field may act as a key element for generation of strong quantum correlations. Besides, superconducting microwave cavities offer an excellent platform for experimental studies of such quantum effects. In this work, we numerically investigate vacuum correlations in a flux-tunable superconducting cavity under multiple pump tones. We consider double and triple pumping cases and explore pairwise correlations between three frequency bands specified within a single cavity resonance. Our work shows that three pumps produce more correlations than two pumps; thus, quantum resources facilitated by the triple pump scheme offers enhanced prospects for quantum data processing using parametric microwave cavities.
Abstract It is proposed that how to generate and amplify multipartite entanglement simply by applying two microwave parametric amplifiers (MPAs) in a cascaded system without parametric downconversion interactions. Both the bipartite and tripartite entanglement of the three‐mode bosonic system are induced via the nonlinear gain of the two MPAs, which does not require strong coherent parametric coupling. Simultaneously, the intrinsic dissipation and detuning of the quadrature modes are corrected by modulating the phase difference of the MPAs, which directly changes the photon statistical distribution of the microwave cavity, so that both bipartite and tripartite entanglement of the dual‐cavity‐magnon system can be significantly enhanced. In particular, the phase‐modulated (PM) tripartite entanglement reaches the degree of 0.1 and breaks the limit of weak tripartite entanglement (on the degree of 0.01 and 0.001), which is a milestone breakthrough. More importantly, the PM multipartite entanglement is axisymmetric or centrosymmetric with respect to detuning and phase difference, which provides a bidirectional parameter selection for the experimental preparation of strong steady‐state entanglement. Furthermore, the PM multipartite entanglement is accompanied by improved robustness against the thermal bath temperature. The phase modulation mechanism can be potentially applied to construct stable multipartite entanglement networks and quantum information processing.
Abstract A scheme is proposed to enhance quantum correlation, including entanglement and steering, for two magnon modes in a cavity‐magnon hybrid system through coherent quantum feedback. The hybrid system consists of a microwave cavity and two YIG spheres, which incorporates a nonlinear flux‐driven Josephson parametric amplifier in order for the generation of two photons within the cavity simultaneously. A quantum coherent feedback loop is used for the reduction of effective dissipation. By modulating feedback parameters, optimal bipartite and tripartite entanglement, as well as quantum steering are derived. Importantly, compared with the same setup without coherent feedback, the proposed scheme significantly improves quantum correlation. Furthermore, by optimizing the feedback reflectivity and the ratio of cavity‐magnon coupling strength, the enhancement of asymmetric steering can be controlled. Notably, incorporating the feedback loop effectively increase its robustness against thermal noise, thus the scheme offer better prospect for experimental development. This study paves the way for advancements in quantum information processing and quantum entanglement within cavity‐magnonics.
We present an alternative scheme for the generation of the entangled microwave radiation with amplification in single triple-Λ five-level molecular magnets driven by two strong control fields and one relative weak pump field. By numerically simulating the dynamics of the system, we show that three fully entangled modes with different frequencies can be obtained in the presence of the relaxations. Our numerical results also show that the entanglement occurs among the three cavity fields with a large number of photons. Physically, the responsible mechanism is quantum coherence. Two strong control fields induce two cavity modes coupled with the strong-driven levels to a quantum beat, and then the relative weak pump field leads to the parametric interaction between such a beat with the third mode coupled with the weak-driven level. The present work provides an efficient approach to achieve tripartite continuous-variable entanglement in the molecular magnets system, which may be necessary for the progress of solid-state quantum information.