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Phononic-waveguide-assisted steady-state entanglement of silicon-vacancy centers
摘要： Multiparticle entanglement is of great significance for quantum metrology and quantum information processing. We present here an efficient scheme for generating stable multiparticle entanglement in a solid-state setup, where an array of silicon-vacancy centers are embedded in a quasi-one-dimensional acoustic diamond waveguide. In this scheme, the continuum of phonon modes induces a controllable dissipative coupling among the SiV centers. We show that, by an appropriate choice of the distance between the SiV centers, the dipole-dipole interactions can be switched off due to destructive interference, thus realizing a Dicke superradiance model. This gives rise to an entangled steady state of SiV centers with high fidelities. The protocol provides a feasible setup for the generation of multiparticle entanglement in a solid-state system.
关键词： Multiparticle entanglement,quantum information processing,acoustic diamond waveguide,quantum metrology,silicon-vacancy centers,Dicke superradiance model
更新于2025-09-19 17:13:59
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Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth from single-mode PPLN waveguide
摘要： Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO3 waveguide, which is directly bonded onto a LiTaO3 substrate. The single-pass OPA allows THz bandwidth, and the absence of higher-order spatial modes in the single-spatial-mode structure helps avoid degradation of squeezing. In addition, the directly bonded ZnO-doped waveguide has durability for high-power pump and shows small photorefractive damage. Using this waveguide, we observe CW 6.3-dB squeezing at 20-MHz sideband by balanced homodyne detection. This is the first realization of CW squeezing with a single-pass OPA at a level exceeding 4.5 dB, which is required for the generation of a two-dimensional cluster state. Furthermore, the squeezed light shows 2.5-THz spectral bandwidth. The squeezed light will lead to the development of a high-speed on-chip quantum processor using TDM with a centimeter-order optical delay line.
关键词： terahertz-bandwidth,quantum information processing,squeezed light,continuous-wave,single-mode PPLN waveguide
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Development of SPAD Based on Thermoelectrically Controlled Silicon Carbide Avalanche Photodiode
摘要： Single photon detectors, which are capable of ultra-sensitive detection in a low light level, have been widely used in a variety of applications such as remote sensing, biochemical science, and quantum information science. In particular, the rapid development of quantum information science has greatly improved the development of single photon detectors because it played a key role in achieving successful results in quantum key distribution and quantum communication. The single photon avalanche photodiodes (SPADs) are most conventional devices to detect photons because the APDs, the core elements of SPADs, are known to be advantageous to achieve cheap production and robust structure. In recent years, as the demand for ultraviolet light detection has increased, there have been actively reported on the development of APD detectors based on silicon carbide (SiC), which has a high gain only in the deep ultraviolet wavelength band. Here we report on the performance evaluation of lab-assembled SPAD based on SiC-APD.
关键词： ultraviolet light detection,quantum information science,Single photon detectors,SPAD,SiC-APD
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Frequency-Multiplexed Singly-Resonant Photon Pairs from a Quadratic Nonlinear Waveguide Resonator
摘要： Frequency multiplexed photon pair generation has been actively studied for efficient and large-scale photonic quantum information processing [1-3]. In these demonstrations, photon pair generators were realized by using an optical parametric oscillator (OPO) far below threshold; a nonlinear optical medium was inside or integrated with an optical cavity, and a sufficiently weak pump light for the photon pair generation was used. However, to the best of our knowledge, all of the previous demonstrations for frequency multiplexed photon pair generation have used a doubly-resonant OPO which confines both the signal and the idler photons, or a triply-resonant OPO which additionally confines the pump light. In this study, we demonstrate a frequency multiplexed photon pair generation based on a singly-resonant (SR) OPO configuration which confines only one half of the photon pair. We used a periodically-poled lithium niobate (PPLN) waveguide as a monolithically-integrated quadratic nonlinear waveguide resonator; dielectric multilayers are directly formed at the end faces of the PPLN waveguide such that only the signal photon around 1600 nm of the photon pair is confined in the resonator and the idler photon around 1522 nm and the pump light at 780 nm are not confined. In the SR photon pair, in spite of no cavity configuration for the idler photons, not only the signal photons but also the idler photons have comb-like spectra as if both of them are confined in the cavity. In addition, there is not missing teeth region observed in multiple resonant OPO configuration known as the cluster effect [4,5]. As a result, a wide-band frequency multiplexed photon pair generation can be possible. The photon pair generator will be useful for an efficient photonic quantum information processing and a frequency-domain photon manipulation with the use of frequency-domain optical elements [6-9].
关键词： singly-resonant OPO,PPLN waveguide,photon pair generation,quantum information processing,frequency multiplexed
更新于2025-09-16 10:30:52
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Subradiance in multiply excited states of dipole-coupled V-type atoms
摘要： We generalize the theoretical modeling of collective atomic super- and subradiance to the multilevel case including spontaneous emission from several excited states towards a common ground state. We show that in a closely packed ensemble of N atoms with N ? 1 distinct excited states each, one can find a new class of non-radiating dark states, which allows for long-term storage of N ? 1 photonic excitations. Via dipole-dipole coupling only a single atom in the ground state is sufficient in order to suppress the decay of all N ?1 other atoms. By means of some generic geometric configurations, like a triangle of V-type atoms or a chain of atoms with a J = 1 → J = 0 transition, we study such subradiance including dipole-dipole interactions and show that even at finite distances long lifetimes can be observed. While generally hard to prepare deterministically, we identify various possibilities for a probabilistic preparation via a phase-controlled laser pump and decay.
关键词： subradiance,dipole-coupled V-type atoms,dark states,quantum information storage,multilevel atoms
更新于2025-09-16 10:30:52
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Self‐Assembled InAs/GaAs Coupled Quantum Dots for Photonic Quantum Technologies
摘要： Coupled quantum dots (CQDs) that consist of two InAs QDs stacked along the growth direction and separated by a relatively thin tunnel barrier have been the focus of extensive research efforts. The expansion of available states enabled by the formation of delocalized molecular wavefunctions in these systems has led to significant enhancement of the already substantial capabilities of single QD systems and have proven to be a fertile platform for studying light–matter interactions, from semi-classical to purely quantum phenomena. Observations unique to CQDs, including tunable g-factors and radiative lifetimes, in situ control of exchange interactions, coherent phonon effects, manipulation of multiple spins, and nondestructive spin readout, along with possibilities such as quantum-to-quantum transduction with error correction and multipartite entanglement, open new and exciting opportunities for CQD-based photonic quantum technologies. This review is focused on recent CQD work, highlighting aspects where CQDs provide a unique advantage and with an emphasis on results relevant to photonic quantum technologies.
关键词： quantum information,quantum dots,coupled quantum dots,quantum optics
更新于2025-09-12 10:27:22
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Experimental measurement of the quantum geometric tensor using coupled qubits in diamond
摘要： Geometry and topology are fundamental concepts, which underlie a wide range of fascinating physical phenomena such as topological states of matter and topological defects. In quantum mechanics, the geometry of quantum states is fully captured by the quantum geometric tensor. Using a qubit formed by an NV center in diamond, we perform the first experimental measurement of the complete quantum geometric tensor. Our approach builds on a strong connection between coherent Rabi oscillations upon parametric modulations and the quantum geometry of the underlying states. We then apply our method to a system of two interacting qubits, by exploiting the coupling between the NV center spin and a neighboring 13C nuclear spin. Our results establish coherent dynamical responses as a versatile probe for quantum geometry, and they pave the way for the detection of novel topological phenomena in solid state.
关键词： Quantum Control,Quantum Information,Quantum Measurement,Quantum Geometry,Topological Physics
更新于2025-09-12 10:27:22
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Distinctive characteristics of carrier-phonon interactions in optically driven semiconductor quantum dots
摘要： We review distinct features arising from the unique nature of the carrier-phonon coupling in self-assembled semiconductor quantum dots. Because of the discrete electronic energy structure, the pure dephasing coupling usually dominates the phonon effects, of which two properties are of key importance: The resonant nature of the dot-phonon coupling, its non-monotonic behavior as a function of energy, and the fact that it is of super-Ohmic type. Phonons do not only act destructively in quantum dots by introducing dephasing, they also offer new opportunities, e.g. in state preparation protocols. Apart from being an interesting model systems for studying fundamental physical aspects, quantum dot and quantum dot-microcavity systems are a hotspot for many innovative applications. We discuss recent developments related to the decisive impact of phonons on key figures of merit of photonic devices like single or entangled photon sources under aspects like indistinguishability, purity and brightness. All in all it follows that understanding and controlling the carrier-phonon interaction in semiconductor quantum dots is vital for their usage in quantum information technology.
关键词： Non-Markovian dynamics,quantum information processing,optical manipulation,Semiconductor quantum dots,carrier-phonon interaction,photonics
更新于2025-09-12 10:27:22
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Entanglement of genuinely entangled subspaces and states: Exact, approximate, and numerical results
摘要： Genuinely entangled subspaces (GESs) are those subspaces of multipartite Hilbert spaces that consist only of genuinely multiparty entangled pure states. They are natural generalizations of the well-known notion of completely entangled subspaces, which by definition are void of fully product vectors. Entangled subspaces are an important tool of quantum information theory as they directly lead to constructions of entangled states, since any state supported on such a subspace is automatically entangled. Moreover, they have also proven useful in the area of quantum error correction. In our recent contribution [M. Demianowicz and R. Augusiak, Phys. Rev. A 98, 012313 (2018)], we have studied the notion of a GES qualitatively in relation to so-called nonorthogonal unextendible product bases and provided a few constructions of such subspaces. The main aim of the present work is to perform a quantitative study of the entanglement properties of GESs. First, we show how one can attempt to compute analytically the subspace entanglement, defined as the entanglement of the least-entangled vector from the subspace, of a GES and illustrate our method by applying it to a new class of GESs. Second, we show that certain semidefinite programming relaxations can be exploited to estimate the entanglement of a GES and apply this observation to a few classes of GESs revealing that in many cases the method provides the exact results. Finally, we study the entanglement of certain states supported on GESs, which is compared to the obtained values of the entanglement of the corresponding subspaces, and find the white-noise robustness of several GESs. In our study we use the (generalized) geometric measure as the quantifier of entanglement.
关键词： Genuinely entangled subspaces,semidefinite programming,quantum error correction,generalized geometric measure,quantum information theory,geometric measure
更新于2025-09-12 10:27:22
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Nonreciprocity in a strongly coupled three-mode optomechanical circulatory system
摘要： In this work, we propose a scheme in three-mode optical systems to simulate a strongly coupled optomechanical system. The nonreciprocity observed in such a three-mode optomechanical circulatory system (OMCS) is explored. To be speci?c, we ?rst derive a quantum Langevin equation (QLE) for the strongly coupled OMCS by suitably choosing the laser ?eld, then we give a condition for the frequency of the laser and the mechanical decay rate, beyond which the optomechanical system has a unidirectional transmission regardless of how strong the optomechanical coupling is. The optomechanically induced transparency is also studied. The present results can be extended to a more general two-dimensional optomechanical system and a planar quantum network, and the prediction is possible to be observed in an optomechanical crystal or integrated quantum superconducting circuit. This scheme paves a way for the construction of various quantum devices that are necessary for quantum information processing.
关键词： Nonreciprocity,quantum Langevin equation,optomechanically induced transparency,quantum information processing,optomechanical circulatory system
更新于2025-09-12 10:27:22