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Review of Basics and Elementary introduction to quantum postulates.

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Presentation on theme: "Review of Basics and Elementary introduction to quantum postulates."— Presentation transcript:

1 Review of Basics and Elementary introduction to quantum postulates

2 Requirements On Mathematics Apparatus Physical states Mathematic entities Interference phenomena Nondeterministic predictions Model the effects of measurement Distinction between evolution and measurement

3 What’s Quantum Mechanics A mathematical framework Description of the world known Rather simple rules but counterintuitive applications

4 Introduction to Linear Algebra Quantum mechanics  The basis for quantum computing and quantum information Why Linear Algebra?  Prerequisities What is Linear Algebra concerning?  Vector spaces  Linear operations

5 Basic linear algebra useful in QM Complex numbers Vector space Linear operators Inner products Unitary operators Tensor products …

6 Dirac-notation: Bra and Ket For the sake of simplification “ket” stands for a vector in Hilbert “bra” stands for the adjoint of Named after the word “bracket”

7 Hilbert Space Fundamentals Inner product space: linear space equipped with inner product Hilbert Space (finite dimensional): can be considered as inner product space of a quantum system Orthogonality: Norm: Unit vector parallel to |v  :

8 Hilbert Space (Cont’d) Orthonormal basis: a basis set where Can be found from an arbitrary basis set by Gram-Schmidt Orthogonalization

9 Inner Products Inner Product is a function combining two vectors It yields a complex number It obeys the following rules



12 Unitary Operator An operator U is unitary, if Preserves Inner product

13 Tensor Product Larger vector space formed from two smaller ones Combining elements from each in all possible ways Preserves both linearity and scalar multiplication

14 Mathematically, what is a qubit ? (1) We can form linear combinations of states A qubit state is a unit vector in a two dimensional complex vector space

15 Qubits Cont'd We may rewrite as… From a single measurement one obtains only a single bit of information about the state of the qubit There is "hidden" quantum information and this information grows exponentially We can ignore e i  as it has no observable effect

16 Any pair of linearly independent vectors can be a basis!

17 1/  2

18 Bloch Sphere

19 Measurements

20 Postulates in QM Why are postulates important?  … they provide the connections between the physical, real, world and the quantum mechanics mathematics used to model these systems - Isaak L. Chuang 2424

21 Physical Systems - Quantum Mechanics Connections Postulate 1 Isolated physical system  Hilbert Space Postulate 2 Evolution of a physical system  Unitary transformation Postulate 3 Measurements of a physical system  Measurement operators Postulate 4 Composite physical system  Tensor product of components entanglement

22 Summary on Postulates

23 Postulate 3 in rough form


25 From last slide

26 Manin was first compare

27 You can apply the constant to each Distributive properties Postulate 4

28 Entanglement


30 Some convenctions implicit in postulate 4

31 We assume the opposite Leads to contradiction, so we cannot decompose as this Entangled state as opposed to separable states

32 Composite quantum system


34 This was used before CV was invented. You can verify it by multiplying matrices

35 The Measurement Problem Can we deduce postulate 3 from 1 and 2? Joke. Do not try it. Slides are from MIT.

36 Quantum Computing Mathematics and Postulates Advanced topic seminar SS02 “Innovative Computer architecture and concepts” Examiner: Prof. Wunderlich Presented by Chensheng Qiu Supervised by Dplm. Ing. Gherman Examiner: Prof. Wunderlich Anuj Dawar, Michael Nielsen Sources

37 Covered in 2007

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