802 research outputs found

    Ultra-high neutrino fluxes as a probe for non-standard physics

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    We examine how light neutrinos coming from distant active galactic nuclei (AGN) and similar high energy sources may be used as tools to probe non-standard physics. In particular we discuss how studying the energy spectra of each neutrino flavour coming from such distant sources and their distortion relative to each other may serve as pointers to exotic physics such as neutrino decay, Lorentz symmetry violation, pseudo-Dirac effects, CP and CPT violation and quantum decoherence. This allows us to probe hitherto unexplored ranges of parameters for the above cases, for example lifetimes in the range 10βˆ’3βˆ’104 10^{-3}-10^{4} s/eV for the case of neutrino decay. We show that standard neutrino oscillations ensure that the different flavours arrive at the earth with similar shapes even if their flavour spectra at source may differ strongly in both shape and magnitude. As a result, observed differences between the spectra of various flavours at the detector would be signatures of non-standard physics altering neutrino fluxes during propagation rather than those arising during their production at source. Since detection of ultra-high energy (UHE) neutrinos is perhaps imminent, it is possible that such differences in spectral shapes will be tested in neutrino detectors in the near future. To that end, using the IceCube detector as an example, we show how our results translate to observable shower and muon-track event rates.Comment: 16 pages, 10 figure

    Quantum metrology with nonclassical states of atomic ensembles

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    Quantum technologies exploit entanglement to revolutionize computing, measurements, and communications. This has stimulated the research in different areas of physics to engineer and manipulate fragile many-particle entangled states. Progress has been particularly rapid for atoms. Thanks to the large and tunable nonlinearities and the well developed techniques for trapping, controlling and counting, many groundbreaking experiments have demonstrated the generation of entangled states of trapped ions, cold and ultracold gases of neutral atoms. Moreover, atoms can couple strongly to external forces and light fields, which makes them ideal for ultra-precise sensing and time keeping. All these factors call for generating non-classical atomic states designed for phase estimation in atomic clocks and atom interferometers, exploiting many-body entanglement to increase the sensitivity of precision measurements. The goal of this article is to review and illustrate the theory and the experiments with atomic ensembles that have demonstrated many-particle entanglement and quantum-enhanced metrology.Comment: 76 pages, 40 figures, 1 table, 603 references. Some figures bitmapped at 300 dpi to reduce file siz

    λΉ›μ˜ 이쒅 μ–‘μž μ–½νž˜μ„ ν†΅ν•œ 손싀에 κ°•ν•œ μ–‘μžκ³΅κ°„μ΄λ™

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    ν•™μœ„λ…Όλ¬Έ (박사) -- μ„œμšΈλŒ€ν•™κ΅ λŒ€ν•™μ› : μžμ—°κ³Όν•™λŒ€ν•™ λ¬Όλ¦¬Β·μ²œλ¬Έν•™λΆ€(물리학전곡), 2021. 2. μ •ν˜„μ„.The optical system is one of the promising candidates for quantum information processing. Using quantum resources possible for the optical state, one can gain quantum advantages in many useful applications. Quantum teleportation is one of the outstanding protocols using entanglement. However, the unavoidable photon loss damages the entanglement, especially for the optical qubit having many photons. This dissertation discusses the usage of the hybrid entanglement between two different qubit encodings to achieve both the high teleportation success probability and the high fidelity between the input and target qubit. For the high success probability, I utilize the many-photon qubit encoding such as the coherent-state qubit with large amplitude and multiphoton qubit of polarized photons since these encodings have the nearly-deterministic Bell-state measurement schemes. The small-photon qubit encoding, in contrast, shows the better behavior on the photon loss. This encoding includes a vacuum-and-single-photon (VSP) qubit, polarized single-photon (PSP) qubit, and coherent-state qubit with a small amplitude. I consider the hybrid entanglement for a coherent-state qubit to a VSP qubit and a multiphoton qubit to all small-photon qubits. First, the analysis of the hybrid entanglement of a coherent-state qubit shows that the success probability withstands more photon losses as the amplitude of coherent-state qubit increases. The fidelity is affected by the losses both on the coherent-state qubit and VSP qubit, but the loss of the coherent-state qubit affects it more severely especially for large amplitude. Second, the hybrid entanglement of a multiphoton qubit shows that the fidelity is determined by the loss of the small-photon qubit side while the success probability depends on loss only in the multiphoton qubit side. Especially, the hybrid entanglement with the VSP qubit tolerates 10 times more photon-loss rate than the direct transmission in high fidelity regime (F>90%). For the success probability, I propose the optimal photon number consisting of a multiphoton qubit. The generation methods for the required entangled states are additionally discussed. I further investigate the quantum resources of light other than entanglement: coherence and nonclassicality. I propose physically motivated coherence measures from the role of coherence in the quantum Fisher information and expectation values of quantum observables. For the latter measure, the semidefinite programming provides an efficient method to compute the involved optimization. The suggested nonclassicality measure is based on the negativity of the Glauber-Sudarshan P function. The singular behavior of the P function is dealt with by the filtering on the Fourier space. The negativity is proven to be equivalent to the robustness of mixing with the classical state, which gives its operational meaning.κ΄‘ν•™ μ‹œμŠ€ν…œμ€ μ–‘μž 정보 μ²˜λ¦¬μ—μ„œ μœ λ§ν•œ 후보 쀑 ν•˜λ‚˜μ΄λ©° μ–‘μž μžμ›μ„ ν™œμš©ν•˜μ—¬ μ–‘μžμ  이점을 얻을 수 μžˆλŠ” λ§Žμ€ μ‘μš©μ΄ μ‘΄μž¬ν•œλ‹€. μ–‘μž ν…”λ ˆν¬ν…Œμ΄μ…˜μ€ 잘 μ•Œλ €μ§„ ν”„λ‘œν† μ½œ 쀑 ν•˜λ‚˜λ‘œμ„œ μ–‘μž μ–½νž˜μ„ μ΄μš©ν•œλ‹€. κ·ΈλŸ¬λ‚˜ κ΄‘μž 손싀은 μ–‘μž μ–½νž˜μ— λΆˆκ°€ν”Όν•˜κ²Œ 손상을 μ£Όκ³ , μ΄λŠ” λ§Žμ€ κ΄‘μžλ‘œ κ΅¬μ„±λœ νλΉ—μ˜ 경우 더 μ‹¬κ°ν•œ 영ν–₯을 λΌμΉœλ‹€. 이 논문은 μ„œλ‘œ λ‹€λ₯Έ 두 μ’…λ₯˜μ˜ 큐빗 인코딩 μ‚¬μ΄μ˜ μ–½νž˜μ„ μ΄μš©ν•˜λŠ” 이쒅 μ–‘μž μ–½νž˜μ„ μ‚¬μš©ν•˜κ³  높은 ν…”λ ˆν¬ν…Œμ΄μ…˜ 성곡 ν™•λ₯ κ³Ό μˆœκ²°μ„±μ„ λ™μ‹œμ— λ‹¬μ„±ν•˜λŠ” 방법에 λŒ€ν•΄ λ…Όμ˜ν•œλ‹€. 높은 성곡 ν™•λ₯ μ„ μœ„ν•΄ 이 λ…Όλ¬Έμ—μ„œλŠ” 거의 확정적인 벨 츑정을 μˆ˜ν–‰ν•  수 μžˆλŠ” 큰 μ§„ν­μ˜ 결맞음 큐빗과 νŽΈκ΄‘λœ κ΄‘μžλ‘œ κ΅¬μ„±λœ λ‹€κ΄‘μž 큐핏을 κ³ λ €ν•œλ‹€. ν•œνŽΈ, 적은 κ΄‘μžλ₯Ό 가진 큐빗듀은 κ΄‘μž 손싀에 μ˜ν•œ 영ν–₯이 μƒλŒ€μ μœΌλ‘œ 적닀. μ΄λŸ¬ν•œ νλΉ—μ˜ ν›„λ³΄λ‘œ 진곡-단일 κ΄‘μž 큐빗, νŽΈκ΄‘λœ 단일 κ΄‘μž 큐빗, μž‘μ€ μ§„ν­μ˜ 결맞음 큐빗이 κ³ λ €λœλ‹€. 큰 μ§„ν­μ˜ 결맞음 큐빗은 진곡-단일 κ΄‘μž 큐빗과 이쒅 μ–½νž˜μ„, 그리고 λ‹€κ΄‘μž 큐빗은 μ„Έκ°€μ§€μ˜ μž‘μ€ κ΄‘μž νλΉ„νŠΈμ— λŒ€ν•œ μ–½νž˜μ„ κ³ λ €ν•œλ‹€. λ¨Όμ €, 큰 μ§„ν­μ˜ 결맞음 큐빗을 μ΄μš©ν•œ 이쒅 μ–‘μž μ–½νž˜μ— λŒ€ν•œ 뢄석은 νλΉ—μ˜ 진폭이 클수둝 성곡 ν™•λ₯ μ΄ 더 λ§Žμ€ κ΄‘μž 손싀에 λŒ€ν•΄μ„œλ„ λ†’κ²Œ μœ μ§€λœλ‹€λŠ” 것이 λ‚˜νƒ€λ‚œλ‹€. μˆœκ²°μ„±μ€ 결맞음 큐빗과 진곡-단일 κ΄‘μž 큐빗 λͺ¨λ‘μ˜ 손싀에 영ν–₯을 λ°›μ§€λ§Œ, 진폭이 클수둝 결맞음 νλΉ—μ˜ 손싀에 λŒ€ν•œ 영ν–₯을 더 크게 λ°›λŠ” 것을 λ³Ό 수 μžˆλ‹€. λ‘˜μ§Έλ‘œ, λ‹€κ΄‘μž νλΉ—μ˜ 이쒅 μ–‘μž μ–½νž˜μ—μ„œλŠ” μˆœκ²°μ„±μ΄ μž‘μ€ κ΄‘μž νλΉ—μ—μ„œ μΌμ–΄λ‚˜λŠ” μ†μ‹€μ—λ§Œ 영ν–₯을 λ°›λŠ” 반면 성곡 ν™•λ₯ μ€ λ‹€κ΄‘μž νλΉ—μ˜ μ†μ‹€μ—λ§Œ 영ν–₯ λ°›μŒμ„ 보인닀. 특히 높은 μˆœκ²°μ„± μ˜μ—­μ—μ„œ (F>90%) 진곡-단일 κ΄‘μž 큐빗은 λ‹€κ΄‘μž 큐빗을 직접 μ „μ†‘ν•˜λŠ” 방법 보닀 10λ°° λ§Žμ€ κ΄‘μž 손싀λ₯ μ„ κ²¬λ”˜λ‹€λŠ” 것을 보인닀. 성곡 ν™•λ₯ μ— λŒ€ν•΄, 이 논문은 주어진 손싀λ₯ μ— λŒ€ν•΄ λ‹€κ΄‘μž νλΉ—μ˜ 졜적의 κ΄‘μž 수 λ˜ν•œ μ œμ‹œν•œλ‹€. μΆ”κ°€μ μœΌλ‘œ 이쒅 μ–‘μž μ–½νž˜μ„ 생성할 수 μžˆλŠ” μ‹€ν—˜μ  방법이 λ…Όμ˜λœλ‹€. 여기에 더 λ‚˜μ•„κ°€ μ–‘μž μ–½νž˜ 외에 빛이 κ°€μ§ˆ 수 μžˆλŠ” μ–‘μž μžμ›μΈ μ–‘μž 결맞음과 비고전성을 μžμ› 이둠 κ΄€μ ν•˜μ—μ„œ 닀룬닀. λ¨Όμ € 결맞음 이둠에 λŒ€ν•΄ μ–‘μž 츑도 세기와 μ–‘μž κ΄€μΈ‘λŸ‰μ˜ ν‰κ· κ°’μ΄λΌλŠ” 물리적인 ν˜„μƒμ— κΈ°μ΄ˆν•œ 츑도λ₯Ό μ œμ‹œν•œλ‹€. ν›„μžμ˜ 경우 μ–‘ν–‰λ ¬ ν”„λ‘œκ·Έλž˜λ°μ„ 톡해 ν•„μš”ν•œ μ΅œμ ν™” 계산을 μˆ˜ν–‰ ν•  수 μžˆμŒμ„ 보인닀. 이 λ…Όλ¬Έμ—μ„œ μ œμ‹œλœ λΉ„κ³ μ „μ„±μ˜ μΈ‘λ„λŠ” κΈ€λΌμš°λ²„-μˆ˜λ‹€λ₯΄μƒ¨ P-ν•¨μˆ˜μ˜ μŒμˆ˜μ„±μ— κΈ°μ΄ˆν•˜λ©°, P-ν•¨μˆ˜μ˜ νŠΉμ΄μ μ„ 필터링을 톡해 푸리에 κ³΅κ°„μ—μ„œ 닀룬닀. μ΄λŸ¬ν•œ μŒμˆ˜μ„±μ€ κ³ μ „ μƒνƒœμ™€ ν˜Όν•©μ„ κ²¬λ””λŠ” 정도와 κ°™λ‹€λŠ” 것을 증λͺ…ν•˜μ—¬, μ‘°μž‘μ μΈ κ΄€μ μ—μ„œ 의미 λ˜ν•œ μ œμ‹œν•œλ‹€.Abstract i I. Introduction 1 II. Hybrid entanglement of light and teleportation of many-photon qubit encodings 5 2.1 Introduction 5 2.2 Photon-loss model 7 2.3 Teleportation using the hybrid entanglement between a VSP qubit and a coherent-state qubit 8 2.3.1 Loss on hybrid entanglement 8 2.3.2 Output state of the teleportation 9 2.3.3 Fidelity 12 2.3.4 Success probability 13 2.4 Teleportation of a multi-photon qubit using a carrier qubit 15 2.4.1 Review of multiphoton qubit 15 2.4.2 Loss on hybrid entangled states 17 2.4.3 Output states and their fidelities 22 2.4.4 Success probabilities 31 2.5 Generation of hybrid entangled states 34 2.6 Remarks 38 III. Operational quantum resources beyond entanglement 43 3.1 Introduction 43 3.2 Measuring coherence via observable quantum effects 45 3.2.1 Preliminaries 45 3.2.2 Coherence and Quantum Fisher Information 47 3.2.3 Coherence measures from quantum observables 54 3.2.4 Examples 63 3.3 Measuring Nonclassicality via negativity 65 3.3.1 Nonclassicality filtering 65 3.3.2 Negativity as a linear optical monotone 70 3.3.3 Operational interpretations of the negativity 72 3.3.4 Approximate nonclassicality monotones 75 3.3.5 Examples 79 3.4 Remarks 81 IV. Conclusion 85 Bibliography 89 Abstract in Korean 103Docto

    The Dynamics of Energy Systems and the Logistic Substitution Model

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    This work is dedicated to the empirical testing and theoretical formulation of an invariant, the logistic learning curve, as it applies to the structural evolution of energy systems and systems related to energy, such as coal mining. The great success of the model in organizing past data, and the insensitivity to major political and economic perturbations of the structures obtained seem to lend great predictive power to this invariant

    Quantum information with Gaussian states

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    Quantum optical Gaussian states are a type of important robust quantum states which are manipulatable by the existing technologies. So far, most of the important quantum information experiments are done with such states, including bright Gaussian light and weak Gaussian light. Extending the existing results of quantum information with discrete quantum states to the case of continuous variable quantum states is an interesting theoretical job. The quantum Gaussian states play a central role in such a case. We review the properties and applications of Gaussian states in quantum information with emphasis on the fundamental concepts, the calculation techniques and the effects of imperfections of the real-life experimental setups. Topics here include the elementary properties of Gaussian states and relevant quantum information device, entanglement-based quantum tasks such as quantum teleportation, quantum cryptography with weak and strong Gaussian states and the quantum channel capacity, mathematical theory of quantum entanglement and state estimation for Gaussian states.Comment: 170 pages. Minors of the published version are corrected and listed in the Acknowledgement part of this versio
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