1 research outputs found
λΉμ μ΄μ’ μμ μ½νμ ν΅ν μμ€μ κ°ν μμ곡κ°μ΄λ
νμλ
Όλ¬Έ (λ°μ¬) -- μμΈλνκ΅ λνμ : μμ°κ³Όνλν 물리·μ²λ¬ΈνλΆ(물리νμ 곡), 2021. 2. μ νμ.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 μμ€ν
μ μμ μ 보 μ²λ¦¬μμ μ λ§ν ν보 μ€ νλμ΄λ©° μμ μμμ νμ©νμ¬ μμμ μ΄μ μ μ»μ μ μλ λ§μ μμ©μ΄ μ‘΄μ¬νλ€. μμ ν
λ ν¬ν
μ΄μ
μ μ μλ €μ§ νλ‘ν μ½ μ€ νλλ‘μ μμ μ½νμ μ΄μ©νλ€. κ·Έλ¬λ κ΄μ μμ€μ μμ μ½νμ λΆκ°νΌνκ² μμμ μ£Όκ³ , μ΄λ λ§μ κ΄μλ‘ κ΅¬μ±λ νλΉμ κ²½μ° λ μ¬κ°ν μν₯μ λΌμΉλ€.
μ΄ λ
Όλ¬Έμ μλ‘ λ€λ₯Έ λ μ’
λ₯μ νλΉ μΈμ½λ© μ¬μ΄μ μ½νμ μ΄μ©νλ μ΄μ’
μμ μ½νμ μ¬μ©νκ³ λμ ν
λ ν¬ν
μ΄μ
μ±κ³΅ νλ₯ κ³Ό μκ²°μ±μ λμμ λ¬μ±νλ λ°©λ²μ λν΄ λ
Όμνλ€. λμ μ±κ³΅ νλ₯ μ μν΄ μ΄ λ
Όλ¬Έμμλ κ±°μ νμ μ μΈ λ²¨ μΈ‘μ μ μνν μ μλ ν° μ§νμ κ²°λ§μ νλΉκ³Ό νΈκ΄λ κ΄μλ‘ κ΅¬μ±λ λ€κ΄μ ννμ κ³ λ €νλ€. ννΈ, μ μ κ΄μλ₯Ό κ°μ§ νλΉλ€μ κ΄μ μμ€μ μν μν₯μ΄ μλμ μΌλ‘ μ λ€. μ΄λ¬ν νλΉμ νλ³΄λ‘ μ§κ³΅-λ¨μΌ κ΄μ νλΉ, νΈκ΄λ λ¨μΌ κ΄μ νλΉ, μμ μ§νμ κ²°λ§μ νλΉμ΄ κ³ λ €λλ€. ν° μ§νμ κ²°λ§μ νλΉμ μ§κ³΅-λ¨μΌ κ΄μ νλΉκ³Ό μ΄μ’
μ½νμ, κ·Έλ¦¬κ³ λ€κ΄μ νλΉμ μΈκ°μ§μ μμ κ΄μ νλΉνΈμ λν μ½νμ κ³ λ €νλ€.
λ¨Όμ , ν° μ§νμ κ²°λ§μ νλΉμ μ΄μ©ν μ΄μ’
μμ μ½νμ λν λΆμμ νλΉμ μ§νμ΄ ν΄μλ‘ μ±κ³΅ νλ₯ μ΄ λ λ§μ κ΄μ μμ€μ λν΄μλ λκ² μ μ§λλ€λ κ²μ΄ λνλλ€. μκ²°μ±μ κ²°λ§μ νλΉκ³Ό μ§κ³΅-λ¨μΌ κ΄μ νλΉ λͺ¨λμ μμ€μ μν₯μ λ°μ§λ§, μ§νμ΄ ν΄μλ‘ κ²°λ§μ νλΉμ μμ€μ λν μν₯μ λ ν¬κ² λ°λ κ²μ λ³Ό μ μλ€. λμ§Έλ‘, λ€κ΄μ νλΉμ μ΄μ’
μμ μ½νμμλ μκ²°μ±μ΄ μμ κ΄μ νλΉμμ μΌμ΄λλ μμ€μλ§ μν₯μ λ°λ λ°λ©΄ μ±κ³΅ νλ₯ μ λ€κ΄μ νλΉμ μμ€μλ§ μν₯ λ°μμ 보μΈλ€. νΉν λμ μκ²°μ± μμμμ (F>90%) μ§κ³΅-λ¨μΌ κ΄μ νλΉμ λ€κ΄μ νλΉμ μ§μ μ μ‘νλ λ°©λ² λ³΄λ€ 10λ°° λ§μ κ΄μ μμ€λ₯ μ 견λλ€λ κ²μ 보μΈλ€. μ±κ³΅ νλ₯ μ λν΄, μ΄ λ
Όλ¬Έμ μ£Όμ΄μ§ μμ€λ₯ μ λν΄ λ€κ΄μ νλΉμ μ΅μ μ κ΄μ μ λν μ μνλ€. μΆκ°μ μΌλ‘ μ΄μ’
μμ μ½νμ μμ±ν μ μλ μ€νμ λ°©λ²μ΄ λ
Όμλλ€.
μ¬κΈ°μ λ λμκ° μμ μ½ν μΈμ λΉμ΄ κ°μ§ μ μλ μμ μμμΈ μμ κ²°λ§μκ³Ό λΉκ³ μ μ±μ μμ μ΄λ‘ κ΄μ νμμ λ€λ£¬λ€. λ¨Όμ κ²°λ§μ μ΄λ‘ μ λν΄ μμ μΈ‘λ μΈκΈ°μ μμ κ΄μΈ‘λμ νκ· κ°μ΄λΌλ 물리μ μΈ νμμ κΈ°μ΄ν μΈ‘λλ₯Ό μ μνλ€. νμμ κ²½μ° μνλ ¬ νλ‘κ·Έλλ°μ ν΅ν΄ νμν μ΅μ ν κ³μ°μ μν ν μ μμμ 보μΈλ€. μ΄ λ
Όλ¬Έμμ μ μλ λΉκ³ μ μ±μ μΈ‘λλ κΈλΌμ°λ²-μλ€λ₯΄μ¨ P-ν¨μμ μμμ±μ κΈ°μ΄νλ©°, P-ν¨μμ νΉμ΄μ μ νν°λ§μ ν΅ν΄ νΈλ¦¬μ 곡κ°μμ λ€λ£¬λ€. μ΄λ¬ν μμμ±μ κ³ μ μνμ νΌν©μ 견λλ μ λμ κ°λ€λ κ²μ μ¦λͺ
νμ¬, μ‘°μμ μΈ κ΄μ μμ μλ―Έ λν μ μνλ€.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