Interaction picture - time evolution operator

In summary, the conversation is about the interaction picture and how to transform a time evolution operator into it. The question is whether one needs to calculate a complex expression to do so.
  • #1
Faust90
20
0
Hey all,

I got some question referring to the interaction picture. For example:

I have the Hamiltonian ##H=sum_k w_k b_k^\dagger b_k + V(t)=H1+V(t)##

When I would now have a time evolution operator:

##T exp(-i * int(H+V))##.

(where T is the time ordering operator)

How can I transform it into the interaction picture?

Do I have to calculate:

##exp[i H(1)t]T exp(-i int(H+V))exp[-i H(1)t]##

This is nearly impossible, isn't it?

Best

(is it possible to use latex here?)
 
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  • #2
I adjusted your post using the double # around your latex expressions and they look a lot better. You can do the same.
 

FAQ: Interaction picture - time evolution operator

What is the interaction picture in quantum mechanics?

The interaction picture is a mathematical tool used in quantum mechanics to simplify the calculation of time evolution of a quantum system under the influence of a time-dependent external potential or force. In this picture, the time evolution is split into two parts - a free evolution governed by the Hamiltonian of the system, and an interaction term that takes into account the external potential. This approach is particularly useful for systems with time-dependent perturbations, such as atoms in an electromagnetic field.

What is the time evolution operator in the interaction picture?

The time evolution operator in the interaction picture is a unitary operator that describes the time evolution of a quantum system under the influence of a time-dependent external potential. It is denoted by UI(t) and is defined as the product of the free evolution operator, U0(t), and the interaction term, UI(t), i.e. UI(t) = U0(t)UI(t). This operator is used to calculate the state of the system at any given time t, given its initial state at t = 0.

What is the difference between the interaction picture and the Schrodinger picture?

In the Schrodinger picture, the time evolution of a quantum system is described by the state vector, which evolves in time according to the Schrodinger equation. In contrast, in the interaction picture, the time evolution of the system is split into a free evolution and an interaction term, making it easier to solve for systems with time-dependent perturbations. The state vector in the interaction picture is then given by multiplying the time evolution operator with the state vector in the Schrodinger picture.

How is the time evolution operator related to the Hamiltonian in the interaction picture?

In the interaction picture, the time evolution operator can be expressed in terms of the Hamiltonian of the system. Specifically, it is given by UI(t) = e-iH0t/he-iHIt/h, where H0 is the free Hamiltonian and HI is the interaction Hamiltonian. This relation allows us to express the time evolution in terms of the Hamiltonian, making it easier to calculate the state of the system at any given time.

What is the significance of the time evolution operator in quantum mechanics?

The time evolution operator plays a crucial role in quantum mechanics as it allows us to calculate the state of a quantum system at any given time, given its initial state. It also helps us understand how the state of a system changes in response to external perturbations, and is essential in studying quantum phenomena such as quantum entanglement and quantum decoherence.

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