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quant-ph2024
Discrete dynamics in the set of quantum measurements
Albert Rico, Karol Życzkowski
A quantum measurement, often referred to as positive operator-valued measurement (POVM), is a set of positive operators summing to identity, $\sum_jP_j=\mathbb{…
quant-ph2024
Multi-Unitary Complex Hadamard Matrices
Wojciech Bruzda, Grzegorz Rajchel-MieldzioÄ, Karol Å»yczkowski
We analyze the set of real and complex Hadamard matrices with additional symmetry constrains. In particular, we link the problem of existence of maximally entangled multipartite st…
quant-ph2024
Minimal-noise estimation of noncommuting rotations of a spin
Jakub Czartowski, Karol Życzkowski, Daniel Braun
We propose an analogue of interferometry to measure rotation of a spin by using two-spin squeezed states. Attainability of the Heisenberg limit for the estimation…