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Probability vector representation of the Schrödinger equation

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How does this relate to the MIC-POVM representation of states? In the QuantumFramework, we have a transformation that turns a quantum state into a probability distribution in a minimal d^2 dimension, not of order d^3, like in your paper. Then, the Schrodinger equation (technically Liouville–von Neumann equation) can also be written in probability vector form.

We've made this a special case for evolution in phase space. For example, given random Hamiltonian and initial state, you can inspect what equations it generates for NDSolve: equations = Normal @ QuantumEvolve[QuantumOperator["RandomHermitian"], QuantumWignerMICTransform[QuantumState["RandomMixed"]], {t, 0, 1}, "ReturnEquations" -> True] For a qubit, the initial vector would be a 4-dimension probability distribution. Of course, not every 4-dimension probability distribution would correspond to a valid qubit.

POSTED BY: Nikolay Murzin

Dear Nikolay,

thank you for your comment. I’m not familiar with this particular representation, but if you’re referring to works such as https://arxiv.org/abs/2006.13727, then it seems to me that this is fundamentally different. Our aim is to discuss Leggett-Garg inequalities, and thus we need to be able to distinguish physical observables (observed and disturbed). Our probability vector representation allows for such a distinction. On the other hand, the MIC-POVM measurement cannot distinguish the observables since the POVM measurement provides all of the probabilities at once by measuring quantum devices with larger dimensions. Consequently, the MIC-POVM representation cannot be used to investigate assumptions underlying the formulation of Leggett-Garg inequalities such as noninvasive measurability.

Lastly, please note that the dimension of probability vectors associated with generic N-level qudit states in our construction is N(N^2-1). For more details, please refer to Sec. II of https://arxiv.org/abs/2312.16281.

All the best,

Sebastian

POSTED BY: Sebastian Murk

You may find it helpful. I've formulated the temporal version of the CHSH game in analogy to the spatial one, which I've studied here: https://community.wolfram.com/groups/-/m/t/3026423. It is mainly based on this paper: https://arxiv.org/pdf/1005.3421.pdf.

POSTED BY: Nikolay Murzin

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