Can Quantum Mechanics Ket and Bra Methods Solve Scalar Equations?

  • #1
Ugnius
54
10
Homework Statement
##\left|m\right\rangle = \frac{1}{\sqrt{A}}\binom{1-2i}{\alpha} , \left|n\right\rangle = \frac{1}{\sqrt{14}}\binom{-3+2i}{\beta}##
Relevant Equations
Find unknown constants A, α and β, we know that β is real positive integer , α has both real and imaginary parts
Not really even sure how to approach this problem , I would guess if we need scalar answer we would need to combine these two given equations together but I'm unfamiliar with such methods, in the book there is methods to make a ket to a bra and then matrix part transposes and multiplies with the original while constant squares like:
##\left\langle m \right|\left|m\right\rangle = ({\frac{1}{\sqrt{A}}}^2)*\binom{1-2i}{\alpha}*(1-2i ,\alpha)##

Would that be an approach?
 
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  • #2
Ugnius said:
Homework Statement: ##\left|m\right\rangle = \frac{1}{\sqrt{A}}\binom{1-2i}{\alpha} , \left|n\right\rangle = \frac{1}{\sqrt{14}}\binom{-3+2i}{\beta}##
Relevant Equations: Find unknown constants A, α and β, we know that β is real positive integer , α has both real and imaginary parts

Not really even sure how to approach this problem , I would guess if we need scalar answer we would need to combine these two given equations together but I'm unfamiliar with such methods, in the book there is methods to make a ket to a bra and then matrix part transposes and multiplies with the original while constant squares like:
##\left\langle m \right|\left|m\right\rangle = ({\frac{1}{\sqrt{A}}}^2)*\binom{1-2i}{\alpha}*(1-2i ,\alpha)##

Would that be an approach?
If you normalize ##\mid n \rangle##, then yes, you can find ##\beta##. But you would write this as
##\langle n \mid n \rangle = \dfrac{1}{\sqrt{14}} \begin{pmatrix} -3-2i & \beta^* \end{pmatrix} \dfrac{1}{\sqrt{14}} \begin{pmatrix} -3+2i \\ \beta \end{pmatrix}##
(You wrote your bra and ket in the wrong order for ##\langle m \mid m \rangle## in your OP.)

We know that ##\beta## is real, so ##\beta^* = \beta##, and you can go from there.

To find A and ##\alpha## we need to know something about how ##\mid m \rangle## and ##\mid n \rangle## relate to each other. Are they orthogonal? ie. ##\langle n \mid m \rangle = 0##?

-Dan
 
  • #3
Thank you.
They are orthogonal yes , I'm brute forcing the solution right now , I solved for \beta. Now I need to solve \langle n \mid m \rangle = 0 and i'll get back to you for confirmation if I did it correctly
 

FAQ: Can Quantum Mechanics Ket and Bra Methods Solve Scalar Equations?

What are Ket and Bra methods in Quantum Mechanics?

Ket and Bra methods, also known as Dirac notation, are a mathematical formalism used in quantum mechanics to describe quantum states. A "ket" (denoted as |ψ⟩) represents a column vector in a complex vector space, while a "bra" (denoted as ⟨φ|) represents a row vector, which is the Hermitian conjugate of a ket. These notations simplify the representation of quantum states and the operations performed on them.

Can Ket and Bra methods be used to solve scalar equations?

Ket and Bra methods are primarily designed for dealing with linear operators and vector spaces in quantum mechanics. While they are not typically used to solve scalar equations directly, they can be employed to solve problems where scalar quantities arise from operations on quantum states, such as expectation values or inner products. In these cases, the methods help to simplify and organize the calculations.

What is an example of using Ket and Bra notation to solve a problem involving scalars?

One common example is calculating the expectation value of an operator. If you have an operator \(\hat{A}\) and a quantum state |ψ⟩, the expectation value is given by ⟨ψ| \(\hat{A}\) |ψ⟩. This scalar value can be interpreted as the average measurement outcome of the operator \(\hat{A}\) when the system is in state |ψ⟩. The bra-ket notation simplifies the expression and helps in performing the necessary linear algebra operations.

Are there limitations to using Ket and Bra methods for scalar equations?

Yes, Ket and Bra methods are not universally applicable to all scalar equations, especially those that do not involve linear operators or quantum states. They are most effective in the context of quantum mechanics and linear algebra. For purely scalar equations that do not have a natural representation in a vector space, traditional mathematical methods are more appropriate.

How do Ket and Bra methods compare to other mathematical techniques for solving equations?

Ket and Bra methods offer a powerful and compact way to handle problems in quantum mechanics, particularly those involving linear operators and vector spaces. They provide a clear and structured approach to complex problems that might be cumbersome with traditional techniques. However, for purely scalar equations or problems outside the realm of quantum mechanics, other mathematical techniques such as calculus, algebra, or numerical methods may be more suitable and straightforward.

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