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Supersymmetric Polarization Anomaly in Photonic Discrete-Time Quantum Walks
摘要： Quantum anomalies lead to finite expectation values that defy the apparent symmetries of a system. These anomalies are at the heart of topological effects in electronic, photonic, and atomic systems, where they result in a unique response to external fields but generally escape a more direct observation. Here, we implement an optical-network realization of a discrete-time quantum walk, where such an anomaly can be observed directly in the unique circular polarization of a topological midgap state. We base the system on a single-step protocol overcoming the experimental infeasibility of earlier multistep protocols. The evolution combines a chiral symmetry with a previously unexplored unitary version of supersymmetry. Having experimental access to the position and the coin state of the walker, we perform a full polarization tomography and provide evidence for the predicted anomaly of the midgap states. This approach opens the prospect to dynamically distill topological states for quantum information applications.
关键词： quantum anomalies,supersymmetry,polarization,discrete-time quantum walks,topological states
更新于2025-09-23 15:23:52
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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) - Interaction of Topological States of Sounds and Light with Solid-State Emitters as a Quantum Hybrid Platform
摘要： A large set of physically different platforms are still in the race, as promising quantum systems, to perform efficient quantum information processing. Each of them offer particular figures of merit and weaknesses. An important paradigm for quantum computation is to consider hybrid systems where the strengths of different systems can be harvested while mitigating their weaknesses [1]. Meanwhile, increasing efforts are being devoted to topological phases of matter in bosonic systems to perform robust manipulation of quantum information, where topologically protected edge states can be utilized as quantum channels [2]. In this work, we propose a two-dimensional array of driven optomechanical nano-cavities coupled to Silicon-Vacancy (SiV) centres as a versatile quantum hybrid system where a rich set of topological phases for sound and light is present. More precisely, we consider the well-established snowflake architecture where strongly interacting photonic and acoustic modes can be localised in any crystalline arrangement on a free-standing micro-scale chip [3]. The novel element of this work is the addition of the nonlinear system in the SiV centres coupled to the cavities vibrational modes via strain-coupling [4]. Such defects play the role of highly tunable spin qubits that efficiently couple to the propagating acoustic modes within the array. The topological states of joint mechanical and optical modes (polaritons) can open channels for robust transport between distant SiV centres while offering a way to optically probe the dynamics during the transport. For example, regimes in which the acoustic and optical modes are weakly coupled allow the generation of chiral and robust phononic edge states where one could tune in time their coupling to the SiV defects, leading to a single-mode phononic network. In this case, we describe high-fidelity state transfer between distant centres for experimentally relevant parameter regimes. In addition to robust state transfer between distant qubits, we investigate the effects of the nonlinearity generated by the defects on the topological phases of the polaritonic modes. In this context, we describe the topological phases in different regimes of experimental relevance.
关键词： optomechanical nano-cavities,sound and light,solid-state emitters,quantum hybrid platform,Silicon-Vacancy centres,topological states
更新于2025-09-16 10:30:52
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Corner states of light in photonic waveguides
摘要： The recently established paradigm of higher-order topological states of matter has shown that not only edge and surface states but also states localized to corners, can have robust and exotic properties. Here we report on the experimental realization of novel corner states made out of visible light in three-dimensional photonic structures inscribed in glass samples using femtosecond laser technology. By creating and analysing waveguide arrays, which form two-dimensional breathing kagome lattices in various sample geometries, we establish this as a platform for corner states exhibiting a remarkable degree of flexibility and control. In each sample geometry we measure eigenmodes that are localized at the corners in a finite frequency range, in complete analogy with a theoretical model of the breathing kagome. Here, measurements reveal that light can be ‘fractionalized,’ corresponding to simultaneous localization to each corner of a triangular sample, even in the presence of defects.
关键词： corner states,breathing kagome lattices,femtosecond laser technology,higher-order topological states,photonic waveguides
更新于2025-09-11 14:15:04