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- 摘要
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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) - Experimental Violation of Bell's Inequality for Temporal Orders
摘要： Entanglement is a prediction of quantum mechanics that suggests that our physical laws cannot be described by a local causal model. This has led to much debate, including Einstein’s famous suggestion that quantum mechanics is an incomplete theory, and we may one day discover a deeper theory that can be described by a locally causal model. However, loophole free violations of Bell inequalities demonstrate that this is not the case. Bell’s theorem is independent of quantum mechanics, and it shows that any theory attempting to supplant quantum mechanics must be somehow nonlocal. Since then, there have been many experimental violations of Bell inequalities using different physical systems, culminating in three loophole-free experiments [1-3]. Very recent theoretical [4, 5] and experimental techniques [6, 7] have enabled the study of a new phenomenon predicted by quantum mechanics. Namely, the existence of processes without a fixed causal order. Previous experimental tests of this effect, required the assumption that quantum mechanics can be used to correctly model the experimental results. However, just as the study of entanglement before Bell, these results could still be described by some other theory in which the causal order is definite. The question, then, naturally arises do such processes really exist, or are they an artefact of the quantum mechanics. Here we show that these effects are indeed real by constructing a Bell inequality for temporal orders [8]. The violation of this equality implies, independent of quantum mechanics, that the temporal order of the process under study must have been truly indefinite. We then show we can violate this inequality using a system consisting of two quantum SWITCHes [6,7] with entangled control qubits (see Fig. 1).
关键词： quantum mechanics,Bell’s inequality,quantum SWITCH,entanglement,temporal order
更新于2025-09-16 10:30:52
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Electrons in Solids (Mesoscopics, Photonics, Quantum Computing, Correlations, Topology) || 4. Correlated electrons in complex transition metal oxides
摘要： In the previous chapters of this book, we have discussed the consequences of quantum mechanics on the properties of solid state electrons mostly on the single or two particle level. This revealed the important influence of the phase of the electronic wave functions in mesoscopic electronic transport and a general understanding of the optical properties of solids, where the interaction between the electrons led only to relatively simple modifications such as the excitonic binding energy ERyd,X or the dielectric constant of the material ε. In addition, we have learned how to gain an unprecedented control of the quantum mechanical properties, including the dynamics, for single-electron and two-electron systems in spin qubits or in many-particle states in superconducting qubits. There, the electron-electron interaction was mostly used as an exchange coupling or as a classical repulsive energy for read-out.
关键词： spin qubits,electron-electron interaction,mesoscopic electronic transport,excitonic binding energy,superconducting qubits,dielectric constant,solid state electrons,quantum mechanics,optical properties of solids
更新于2025-09-16 10:30:52
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Coded Metasurface with Optical Activity Based on Broadband Asymmetric Transmission of Linearly Polarized Electromagnetic Waves
摘要： Learning models of artificial intelligence can nowadays perform very well on a large variety of tasks. However, in practice, different task environments are best handled by different learning models, rather than a single universal approach. Most non-trivial models thus require the adjustment of several to many learning parameters, which is often done on a case-by-case basis by an external party. Meta-learning refers to the ability of an agent to autonomously and dynamically adjust its own learning parameters or meta-parameters. In this paper, we show how projective simulation, a recently developed model of artificial intelligence, can naturally be extended to account for meta-learning in reinforcement learning settings. The projective simulation approach is based on a random walk process over a network of clips. The suggested meta-learning scheme builds upon the same design and employs clip networks to monitor the agent's performance and to adjust its meta-parameters on the fly. We distinguish between reflex-type adaptation and adaptation through learning, and show the utility of both approaches. In addition, a trade-off between flexibility and learning-time is addressed. The extended model is examined on three different kinds of reinforcement learning tasks, in which the agent has different optimal values of the meta-parameters, and is shown to perform well, reaching near-optimal to optimal success rates in all of them, without ever needing to manually adjust any meta-parameter.
关键词： Machine learning,quantum mechanics,reinforcement learning,adaptive algorithm,random processes,learning,meta-learning
更新于2025-09-16 10:30:52
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Direct Measurement of a Nonlocal Entangled Quantum State
摘要： Entanglement and the wave function description are two of the core concepts that make quantum mechanics such a unique theory. A method to directly measure the wave function, using weak values, was demonstrated by Lundeen et al. [Nature 474, 188 (2011)]. However, it is not applicable to a scenario of two disjoint systems, where nonlocal entanglement can be a crucial element, since that requires obtaining weak values of nonlocal observables. Here, for the first time, we propose a method to directly measure a nonlocal wave function of a bipartite system, using modular values. The method is experimentally implemented for a photon pair in a hyperentangled state, i.e., entangled both in polarization and momentum degrees of freedom.
关键词： modular values,hyperentangled state,Entanglement,weak values,quantum mechanics,wave function
更新于2025-09-16 10:30:52
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Solving method without integration of some differential equation systems for coherent dynamics of quantum media excited by laser radiation
摘要： A pragmatic mechanism to obtain exact analytical solutions of equations describing the coherent dynamics of quantum multilevel systems by laser radiation is implemented. The technique shows interesting features and significant connections between different mathematical structures for constructing exact solutions for a large family of quantum systems, and is based on discrete orthogonal polynomials which are used to express the Fourier spectra of the probability amplitudes of an excited quantum system.
关键词： Discrete orthogonal polynomials,Dynamical systems in quantum mechanics,Exact solutions,Discrete Fourier transform
更新于2025-09-12 10:27:22
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Probing the limits of correlations in an indivisible quantum system
摘要： We employ a trapped ion to study quantum contextual correlations in a single qutrit using the 5-observable Klyachko, Can, Binicio?glu, and Shumovsky inequality, which is arguably the most fundamental noncontextuality inequality for testing quantum mechanics (QM). We quantify the effect of systematics in our experiment by purposely scanning the degree of signaling between measurements, which allows us to place realistic bounds on the nonclassicality of the observed correlations. Our results violate the classical bound for this experiment by up to 25 standard deviations, while being in agreement with the QM limit. In order to test the prediction of QM that the contextual fraction increases with the number of observables, we gradually increase the complexity of our measurements from 5 up to 121 observables. We ?nd stronger-than-classical correlations in all prepared scenarios up to 101 observables, beyond which experimental imperfections blur the quantum-classical divide.
关键词： quantum contextuality,noncontextuality inequality,contextual fraction,quantum mechanics,trapped ion
更新于2025-09-10 09:29:36
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High-dimensional one-way quantum processing implemented on d-level cluster states
摘要： Taking advantage of quantum mechanics for executing computational tasks faster than classical computers or performing measurements with precision exceeding the classical limit requires the generation of specific large and complex quantum states. In this context, cluster states are particularly interesting because they can enable the realization of universal quantum computers by means of a ‘one-way’ scheme, where processing is performed through measurements. The generation of cluster states based on sub-systems that have more than two dimensions, d-level cluster states, provides increased quantum resources while keeping the number of parties constant, and also enables novel algorithms. Here, we experimentally realize, characterize and test the noise sensitivity of three-level, four-partite cluster states formed by two photons in the time and frequency domain, confirming genuine multi-partite entanglement with higher noise robustness compared to conventional two-level cluster states. We perform proof-of-concept high-dimensional one-way quantum operations, where the cluster states are transformed into orthogonal, maximally entangled d-level two-partite states by means of projection measurements. Our scalable approach is based on integrated photonic chips and optical fibre communication components, thus achieving new and deterministic functionalities.
关键词： quantum mechanics,entanglement,photonic chips,high-dimensional quantum computation,cluster states
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Towards a Photonic Quantum Standard for Mass and Force
摘要： A fundamental standard for measuring small forces can potentially be realized using single photons to transfer a known number of quantized photon momenta using the process of reflection. For such an experiment, a resonant optical cavity will maximize the number of momentum transfers per photon, making it possible to scale the total force generated. We have developed and tested such a system that operates in the many photon regime as a stepping stone towards a photonic quantum force standard.
关键词： measurement,quantum mechanics,standards,Force sensors,optics
更新于2025-09-10 09:29:36
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[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || PT-Symmetry on-a-Chip: Harnessing Optical Loss for Novel Integrated Photonic Functionality
摘要： The development of non-Hermitian parity-time (PT) symmetric quantum mechanics has offered a powerful platform to engineer novel device functionality for integrated photonics. In this chapter, we review the chip-scale applications of PT-symmetry in photonic devices, including the implementation of the unidirectional reflectionless PT metamaterial, coherent asymmetric light-light switching, and orbital angular momentum (OAM) laser on-chip. We study the optical analogy of non-Hermitian PT systems, manipulate the complex refractive index properties such as gain/loss modulation, and investigate the unique wave transport characteristics near the exceptional point (EP) to achieve these intriguing on-chip functionalities.
关键词： light-light switching,orbital angular momentum laser,optical loss,non-Hermitian quantum mechanics,integrated photonics,PT-symmetry,unidirectional reflectionless,exceptional point
更新于2025-09-10 09:29:36
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SEMICONDUCTORS OF CRYSTALLIN ALLOYS IN SUPERLATTICES
摘要： This work analyzes, from the effects related to the processes of transportation of carrier and the changes in the electronic structure of semiconductors materials due to the presence of defects and disorders in the alloys crystalline superlattice. These defects are located in specific areas of the material and either interact or remain inert. In general, they are described by local wave functions. The study of superlattices of semiconductor crystal considers important parameters such as disorder effects in crystals and the alternate periodic growth of the layer of two semiconductors with different gaps and minigaps energies. The quantum mechanical calculations are applied for determining the physical properties of the semiconductors crystals. This study encompasses the effects of defects and the crystalline disorders evaluation by quantum mechanics. Further, the presence of the defects in the periodic, quasiperiodic and disordered arrangements is discussed. The theoretical approach is used to understand the mechanism and the results of experimental techniques in which are characterized the current and optic transportation of a semiconductor crystal.
关键词： Defects,Superlattices,Semiconductors,Quantum Mechanics
更新于2025-09-10 09:29:36