What is a Dual Vector in Bra and Ket Notation?

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SUMMARY

The discussion clarifies the concepts of bra and ket notation in quantum mechanics, specifically defining a ket |ψ> as a column matrix and a bra <ψ| as a row matrix. The dot product is denoted as <ψ|ψ>, while the outer product |ψ><ψ| results in a matrix. The term "dual vector" refers to the relationship between bra and ket vectors, emphasizing their distinct roles in quantum mechanics. A recommended resource for further understanding is the PDF from CSB SJU, which supplements the textbook "Quantum Mechanics" by Brandsen and Joachain.

PREREQUISITES
  • Understanding of basic linear algebra concepts, specifically matrices.
  • Familiarity with quantum mechanics terminology and principles.
  • Knowledge of vector spaces and their duals.
  • Basic comprehension of Dirac notation and its applications in quantum theory.
NEXT STEPS
  • Study the PDF resource on Dirac notation provided in the discussion.
  • Learn about the properties of dual vectors in vector spaces.
  • Explore the mathematical foundations of quantum mechanics, focusing on linear operators.
  • Investigate the implications of bra-ket notation in quantum state representation.
USEFUL FOR

Students of quantum mechanics, physicists, and anyone seeking to deepen their understanding of bra and ket notation and its applications in quantum theory.

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This isn't a homework problem, but it's so simple that it belongs here.

Can someone please explain to me bra and ket notation? I've been consulting various books and they are all so abstract. Yesterday, my professor told me that a ket |ψ> represents a column matrix and a bra <ψ| represents a row matrix, and that's all there is to it. The (dot) product is represented by <ψ|ψ> rather than <ψ||ψ>, and |ψ><ψ| is also a product, though it produces a matrix.

Yes, this all makes sense in terms of matrices. So my first request is that someone explain this to me in modern, matrix notation.

What's this mysterious "dual vector" that all the books allude to in the introduction of bra and kets? Why isn't matrix notation, ψ for column matrix and ψT for row matrix good enough?
 
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I would recommend you reading this:
www.users.csbsju.edu/~frioux/dirac/dirac.pdf
It helped me a lot and we got it from our QM-teacher as a supplement to the book by Brandsen and Joachain named Quantum Mechanics(Descriptive title)
 

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