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[Springer Theses] Quantum Confined Excitons in 2-Dimensional Materials || Introduction: 2d-Based Quantum Technologies
摘要： Framed within the growing giant of quantum technologies, with billions in expenditure world-wide and rapidly growing, we harness the exciting physics and technological promise of 2-dimensional materials to create atomically-thin quantum devices capable of emitting single photons and capturing single spins. In this thesis we present the alliance of 2d and quantum information technology - the first steps towards hybrid light-matter quantum networks set in a low power, scalable on-chip platform.
关键词： quantum technologies,single spins,single photons,quantum networks,2-dimensional materials
更新于2025-09-23 15:21:21
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Direct characterization of linear and quadratically nonlinear optical systems
摘要： A central task in quantum-information processing is to characterize quantum processes. In the realm of optical quantum-information processing, this amounts to characterizing the transformations of the mode creation and annihilation operators. This transformation is unitary for linear optical systems, whereas these yield the well-known Bogoliubov transformations for systems with Hamiltonians that are quadratic in the mode operators. In this paper, we propose a shot-noise limited scheme for characterizing both these kinds of evolutions by employing a modified Mach-Zehnder interferometer. In order to characterize a N -mode device, we require O(N 2) measurements. Although it suffices to use coherent states for the characterization of linear optical systems, we additionally require single photons to characterize quadratically nonlinear optical systems.
关键词： Bogoliubov transformations,Mach-Zehnder interferometer,optical systems,quantum-information processing,coherent states,single photons
更新于2025-09-23 15:21:21
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Heralded single-photon and correlated-photon-pair generation via spontaneous four-wave mixing in tapered optical fibers
摘要： We study the generation of frequency nondegenerate correlated photon pairs and heralded single photons via spontaneous four-wave mixing (SFWM) in a series of identical micro- or nano?bers (MNFs). Joint spectral intensity of the biphoton ?eld generated at wavelengths of about 880 and 1310 nm has been measured under excitation by 100-ps laser pulses demonstrating good agreement with the theoretical prediction. The measured zero-time second-order autocorrelation function was about 0.2 when the emission rate of the heralded photons was of 4 Hz. The MNF-based source perfectly matches standard single-mode ?bers, which makes it compatible with the existing ?ber communication networks. In addition, SFWM observation in a series of identical MNFs allows for increasing the generation rate of single photons via spatial multiplexing.
关键词： heralded single photons,spontaneous four-wave mixing,correlated photon pairs,micro- or nano?bers,quantum optical technologies
更新于2025-09-23 15:21:01
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Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamonds
摘要： The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that SiV centers in nanodiamonds exhibit a strongly inhomogeneous distribution with regard to the center wavelengths and linewidths of the zero-phonon-line (ZPL) emission at room temperature. We find that the SiV centers separate in two clusters: one group exhibits ZPLs with center wavelengths within a narrow range ≈730–742 nm and broad linewidths between 5 and 17 nm, whereas the second group comprises a very broad distribution of center wavelengths between 715 and 835 nm, but narrow linewidths from below 1 up to 4 nm. Supported by ab initio Kohn–Sham density functional theory calculations we show that the ZPL shifts of the first group are consistently explained by strain in the diamond lattice. Further, we suggest, that the second group showing the strongly inhomogeneous distribution of center wavelengths might be comprised of a new class of silicon-related defects. Whereas single photon emission is demonstrated for defect centers of both clusters, we show that emitters from different clusters show different spectroscopic features such as variations of the phonon sideband spectra and different blinking dynamics.
关键词： diamond,single photons,density functional theory calculations,color centers,optical emission,nanodiamond
更新于2025-09-19 17:15:36
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Carbon nanotube color centers in plasmonic nanocavities: A path to photon indistinguishability at telecom bands
摘要： Indistinguishable single photon generation at telecom wavelengths from solid-state quantum emitters remains a significant challenge to scalable quantum information processing. Here we demonstrate efficient generation of indistinguishable single photons directly in the telecom O-band from aryl-functionalized carbon nanotubes by overcoming the emitter quantum decoherence with plasmonic nanocavities. With an unprecedented single-photon spontaneous emission time down to 10 ps (from initially 0.7 ns) generated in the coupling scheme, we show a two-photon interference visibility at 4 K reaching up to 0.79, even without applying post selection. Cavity-enhanced quantum yields up to 74% and Purcell factors up to 415 are achieved with single-photon purities up to 99%. Our results establish the capability to fabricate fiber-based photonic devices for quantum information technology with coherent properties that can enable quantum logic.
关键词： Plasmonic nanocavities,indistinguishable single photons,telecommunication bands,carbon nanotubes
更新于2025-09-12 10:27:22
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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) - Birefringent Cavities: Effects and Applications of a New Paradigm in CQED
摘要： The enhanced interaction of quantum states of light and matter within an optical resonator is a powerful tool for both addressing fundamental questions of nature and pursuing quantum technologies. Here, we discuss the impact of cavity birefringence – a lifting of the degeneracy of polarisation modes within the resonator – on both of these challenges. A novel model for such systems is experimentally veri?ed by the cavity emission of single photons with time-dependent polarisation states that evolve along their wavepacket [1]. This model is then used to demonstrate how a tailored birefringence allows for enhanced photon emission beyond previous limitations [2].
关键词： polarisation states,CQED,optical resonator,quantum states of light and matter,cavity birefringence,single photons,birefringent cavities
更新于2025-09-12 10:27:22
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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) - Quantum Storage of Frequency-Multiplexed Heralded Single Photons
摘要： Quantum memories for light are important devices in quantum information science, in particular for applications such as quantum networks and quantum repeaters [1]. It has been predicted that multimode quantum memories able to store independently multiple modes would greatly help the scaling of quantum networks by decreasing the entanglement generation time between remote quantum nodes [1]. Current research focuses mostly on time multiplexing in rare-earth doped crystals and in spatial multiplexing in atomic gases. Beyond these demonstrations, rare-earth doped crystals, thanks to their large inhomogeneous broadening, represent a unique quantum system which could also add another degree of freedom for multiplexing, the storage of multiple frequency modes [2]. In this contribution, we report on the first demonstration of quantum storage of a frequency multiplexed single photon into a laser-written waveguide integrated in a Pr3+:Y2SiO5 crystal. The great advantage of using a confined waveguide for this task is that the power required to prepare the quantum memory is strongly reduced due to the increased light-matter interaction in the waveguide. This enables simultaneous preparation of several memories at different frequencies, with a moderate laser power.
关键词： quantum repeaters,Quantum memory,single photons,quantum networks,frequency multiplexing
更新于2025-09-11 14:15:04
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Tunable Quantum Beat of Single Photons Enabled by Nonlinear Nanophotonics
摘要： We demonstrate the tunable quantum beat of single photons through the co-development of core nonlinear nanophotonic technologies for frequency-domain manipulation of quantum states in a common physical platform. Spontaneous four-wave mixing in a nonlinear resonator is used to produce nondegenerate, quantum-correlated photon pairs. One photon from each pair is then frequency shifted, without degradation of photon statistics, using four-wave-mixing Bragg scattering in a second nonlinear resonator. Fine tuning of the applied frequency shift enables tunable quantum interference of the two photons as they are impinged on a beam splitter, with an oscillating signature that depends on their frequency difference. Our work showcases the potential of nonlinear nanophotonic devices as a valuable resource for photonic quantum-information science.
关键词： four-wave-mixing Bragg scattering,nonlinear nanophotonics,frequency-domain manipulation,quantum interference,quantum states,quantum beat,single photons,photonic quantum-information science,quantum-correlated photon pairs,spontaneous four-wave mixing
更新于2025-09-11 14:15:04
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Unified treatment of the total angular momentum of single photons via generalized quantum observables
摘要： In this paper, we provide a consistent framework to address the notorious difficult decomposition of the single-photon total angular momentum (TAM) into a spin (SAM) and an orbital (OAM) component. We discuss the canonical decomposition into SAM and OAM components, which are the generators of internal and spatial rotations in the space of physical states. We find that those operators are mutually compatible but unsharp quantum observables, therefore POVM (Positive Operator-Valued Measures) describe their joint measurements. We present another decomposition of the TAM, which we denote as a non-canonical one. The operators resulting from this decomposition are mutually incompatible but sharp quantum observables, thus PVM (Projector-Valued Measurements). This fact reflects their consistency with the transversality condition of single-photon wavefunctions, thus explains the underlying physics from a quantum information theoretic view. Furthermore, we discuss the implementations on joint measurements for both decompositions and provide an explicit calculation of all these quantities for circularly polarized Gaussian single-photon states. The difference between the canonical and non-canonical momenta leads to observable differences in higher-order statistical moments.
关键词： spin angular momentum,total angular momentum,quantum observables,orbital angular momentum,PVM,single photons,POVM
更新于2025-09-09 09:28:46