I Lindbladian Jump Operators Condition

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The discussion centers on the conditions for jump operators in quantum dynamical semigroups, specifically referencing a paper that outlines the requirement that the sum of the adjoint operators must be less than or equal to one. The user questions how equation (8.12) maintains its classification as a quantum-dynamical-semigroup type when this condition appears violated, particularly in relation to the number operator, which is unbounded. The confusion arises from the identification of the jump operators with spatially dependent creation operators and their implications for the boundedness condition. The conversation highlights the nuances of operator theory in quantum mechanics and the specific mathematical frameworks being applied. Clarification on these points is sought to resolve the apparent contradiction.
thatboi
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Hi all,
I am considering the following paper: https://arxiv.org/abs/quant-ph/0302164. Specifically the discussion of the quantum dynamical semigroup equations in section 6.6, where just above equation (6.66), there was the following condition on the jump operators ##A_{i}##: ##\sum_{i\in K_{0}}A_{i}^{\dagger}A_{i} \leq 1## for all ##K_{0} \subset K##. I then looked at equation (8.12), where the author identified ##A_{i}## with ##N(x) = \int d^{3}y \hspace{0.25cm} g(y-x)a^{\dagger}(y)a(y) ## where ##g(x) = \left(\frac{\alpha}{2\pi}\right)e^{-\frac{\alpha}{2}x^{2}}## and ##a^{\dagger}## is the creation operator of a particle (either fermionic or bosonic), and identified the index ##i## with the position in space ##x##. My confusion is why equation (8.12) is still quantum-dynamical-semigroup type when ##\sum_{i\in K_{0}}A_{i}^{\dagger}A_{i} \leq 1## no longer seems to be satisfied. After all, the number operator itself is not a bounded operator right?
 
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