University Advanced Quantum Mechanics · topic UAQM-14.04
The Lindblad form, the GKSL theorem and a thermal reservoir
Connect the ideas, make your working visible, and test the result. Use the hints when you need a starting point; open the full solution after your attempt.
Further practice
Work through a fresh case before tackling the extension.
The Lindblad form, the GKSL theorem and a thermal reservoir: predict a finite change
A Lindblad master equation is a first-order equation for the density operator, built from a Hamiltonian and jump operators Lₖ, whose solution at every later time is a completely positive, trace-preserving map of the initial state. Use the supplied topic model Y_out = (exp(1/temp)-1)/(exp(1/temp)+1), where Y_out is T₁ IN UNITS OF 1/Γ (dimensionless). The output symbol Y_out is distinct from all input symbols. ^ denotes a power; π = 3.141592653589793; exp(x) means eˣ. temp is Temperature k_B T/ħω₀, dimensionless. Keep p0 (Initial excited population pₑ(0)) = 1 fixed. For this exercise use only 0.408125 ≤ temp ≤ 2.69188 on this continuous branch. A grid of test settings is an input restriction for this exercise, not by itself a claim of physical quantisation. This calculation retains the topic model's stated assumptions; it does not extend them to a different physical setup. Calculate Y_out at temp = 0.91055 and 1.23027. Find the signed output change ΔY_out and the average sensitivity ΔY_out/Δtemp across this interval. State whether the response increases or decreases; distinguish this interval average from a derivative at one point.
T₁ IN UNITS OF 1/Γ against temp
Predictions from the supplied The Lindblad form, the GKSL theorem and a thermal reservoir model, with all other inputs fixed as stated in the question. 5 calibration points support a trend comparison; they are not measured data or a straight-line law.
Vertical axis (y): T₁ IN UNITS OF 1/Γ
Horizontal axis (x): temp: Temperature k_B T/ħω₀
Axes show the supplied calibration interval; the origin may lie outside the plot.
Read the exact data as a table
| temp: Temperature k_B T/ħω₀ | T₁ IN UNITS OF 1/Γ |
|---|---|
| 0.40812499999999996 | 0.8411564947415912 |
| 0.9790625 | 0.4704846845216812 |
| 1.5499999999999998 | 0.31183848721073015 |
| 2.1209375 | 0.2314725340747788 |
| 2.691875 | 0.1836370982174719 |
These are the supplied values, not a worked answer. No fitted trend is drawn.
Show a hint
Substitute each value of temp separately while keeping every other input fixed, then subtract in the same order.
Reveal the worked solution
- At temp = 0.91055, substitute into Y_out = (exp(1/temp)-1)/(exp(1/temp)+1): Y₀ = 0.499859.
- At temp = 1.23027, the same fixed-parameter model gives Y₁ = 0.385423.
- Signed change: ΔY_out = Y₁ − Y₀ = -0.114436; the input change is Δtemp = 0.319725.
- Average sensitivity is ΔY_out/Δtemp = -0.357921 1 per unit input. Its negative sign means that this response decreases over the specified interval.
- This is a secant slope between two settings. It equals a point derivative only for a locally linear relation or in a justified small-interval limit.
Answer Y₀ = 0.499859, Y₁ = 0.385423; ΔY_out = -0.114436; average sensitivity = -0.357921 1 per unit input.
Compare the assumptions, method and units with your attempt. Explain any correction before trying another question.
Extra challenging questions
Work through the linked stages and explain what each result means.
The Lindblad form, the GKSL theorem and a thermal reservoir: infer an input with uncertainty
A Lindblad master equation is a first-order equation for the density operator, built from a Hamiltonian and jump operators Lₖ, whose solution at every later time is a completely positive, trace-preserving map of the initial state. Use the supplied topic model Y_out = (exp(1/temp)-1)/(exp(1/temp)+1), where Y_out is T₁ IN UNITS OF 1/Γ (dimensionless). The output symbol Y_out is distinct from all input symbols. ^ denotes a power; π = 3.141592653589793; exp(x) means eˣ. temp is Temperature k_B T/ħω₀, dimensionless. Keep p0 (Initial excited population pₑ(0)) = 1 fixed. For this exercise use only 0.408125 ≤ temp ≤ 2.69188 on this continuous branch. A grid of test settings is an input restriction for this exercise, not by itself a claim of physical quantisation. This calculation retains the topic model's stated assumptions; it does not extend them to a different physical setup. A reading gives Y_out = 0.27067384, with a bounded reading uncertainty ±0.013056. Treat the model and all fixed inputs as exact for this exercise; the bound is not a standard deviation. First estimate the unknown temp by straight-line interpolation between the two endpoint predictions. Then solve the actual model on the stated branch to an absolute input tolerance of 0.000228375, using a numerical bracket if required. Find the full input interval consistent with the bounded reading uncertainty and compare it with a symmetric input-error assumption. Do not assume that the supplied calibration points prove monotonicity outside this branch.
T₁ IN UNITS OF 1/Γ against temp
Predictions from the supplied The Lindblad form, the GKSL theorem and a thermal reservoir model, with all other inputs fixed as stated in the question. 5 calibration points support a trend comparison; they are not measured data or a straight-line law.
Vertical axis (y): T₁ IN UNITS OF 1/Γ
Horizontal axis (x): temp: Temperature k_B T/ħω₀
Axes show the supplied calibration interval; the origin may lie outside the plot.
Read the exact data as a table
| temp: Temperature k_B T/ħω₀ | T₁ IN UNITS OF 1/Γ |
|---|---|
| 0.40812499999999996 | 0.8411564947415912 |
| 0.9790625 | 0.4704846845216812 |
| 1.5499999999999998 | 0.31183848721073015 |
| 2.1209375 | 0.2314725340747788 |
| 2.691875 | 0.1836370982174719 |
These are the supplied values, not a worked answer. No fitted trend is drawn.
Show a hint
The model's endpoint predictions bracket the reading. Solve Y_out(temp) = Y_measured and then solve again at Y_measured − u and Y_measured + u; a nonlinear inverse can give unequal input deviations.
Reveal the worked solution
- Endpoint predictions are Y_out(0.408125) = 0.841156 and Y_out(2.69188) = 0.183637. The target lies between them. On the selected branch the response is strictly decreasing.
- Endpoint interpolation gives temp_line = 0.408125 + (0.270674 − 0.841156)(2.69188 − 0.408125)/(0.183637 − 0.841156) = 2.38957. This estimates the inverse of the endpoint chord, rather than assuming that chord is the physical model.
- Use the actual equation, not the chord, and bracket its root. Evaluating the midpoint and retaining the sign-changing half-interval gives temp = 1.80121; substituting back gives Y_out = 0.27067384.
- The interpolation error in the input is |temp_line − temp| = 0.588359. This is larger than the requested numerical tolerance.
- Invert both limits Y_out = 0.25761784 and 0.28372984. Sort the roots even if the response decreases: 1.71389 ≤ temp ≤ 1.89714.
- The lower and upper input deviations are 0.0873214 and 0.0959231. They differ because the inverse response is nonlinear; a symmetric error bar would only be a local approximation. This interval includes reading uncertainty only, not model error or uncertainty in fixed inputs.
Answer temp ≈ 1.80121; compatible interval [1.71389, 1.89714]. Endpoint interpolation gives 2.38957.
Compare the assumptions, method and units with your attempt. Explain any correction before trying another question.