苏汝铿高等量子力学讲义英文版Chapter7QuantumEntanglementandQuantumInformation课件幻灯片.ppt

§ 7.4 Measurement and decoherence Measurement Wave packet collapse Quantum decoherence The non-diagonal terms of density matrix disappear § 7.4 Measurement and decoherence System A is at the state , while B is at the state . § 7.5 Quantum teleporation § 7.5 Quantum teleporation Motivation Procedure The particle 1 with its spin ? at Alice. § 7.5 Quantum teleporation The particle 2, 3 with its spin ? are at the entangled state EPR pair: In the Bell basis § 7.5 Quantum teleporation If Alice obtain , the particle 3 measured by Bob is § 7.5 Quantum teleporation Measured by Alice Measured by Bob Chapter 7Quantum Entanglement and Quantum Information §7.1 Pure states and mixed states Introduction: Quantum entanglement describes the coherence of two or many quantum states according to the superposition principle of quantum states. Energy: interactions, conservation laws, work… Entropy: information, order and disorder… Entanglement: coherence, teleportation… Pure state §7.1 Pure states and mixed states System A: Systems A+B: Pure state §7.1 Pure states and mixed states Density matrix: In the base of the representation O § 7.1 Pure states and mixed states The average value of a quantity F: § 7.1 Pure states and mixed states Mixed state: the non-coherent mixture of two or many pure states System A: § 7.1 Pure states and mixed states In the base of the representation O § 7.1 Pure states and mixed states Systems A+B: the reduced density matrix If is a observable quantity of system A, its average value: is a unit operator of system B. § 7.1 Pure states and mixed states is called the reduced density matrix. § 7.1 Pure states and mixed states The properties of measurement § 7.1 Pure states and mixed states For a s=1/2 particle: Pure State: Mixed State: The superposition state and its mixed state: § 7.1 Pure states and mixed states The measurement of : Pure State: Mixed State: § 7.1 Pure st