Quantum Journal

Exact Posterior Prediction from Product Haar Measurements and a Randomized-Mesh Maximum-Likelihood Bridge

We study prediction of one unmeasured copy of an unknown finite-dimensional pure quantum state after independently measuring the observed copies with the one-copy Haar POVM. For the resulting fixed separable observation, the Bayes predictive state under quantum relative-entropy loss is the full-rank posterior mean. We evaluate it exactly through permanents of minors of the outcome Gram matrix, prove positivity and normalization of the permanent...

Global and nonlocal magic of quantum many-body scars

Nonergodic features of chaotic quantum many-body systems are commonly characterized through local observables, fidelity, and entanglement entropy. Here, using global and nonlocal measures of nonstabilizerness (magic), we study quantum many-body scars near infinite temperature in $(1+1)$-dimensional Abelian $\mathbb{Z}_2$ and U$(1)$ lattice gauge theories, both analytically and numerically. We derive an exact closed-form expression for the nonloc...

Electrons slow to a crawl in a strange new quantum state

Scientists at the University of Chicago have uncovered a surprising quantum state in the layered magnetic material Fe5GeTe2, where huge numbers of electrons move together unusually slowly while remaining quantum coherent. The behavior contradicts existing theoretical predictions about how the material’s magnetism should work and suggests scientists may need to rethink its underlying physics.

Patenting Quantum Computing Innovations – Part 4: Entanglement Swapping

In part four of our five part series on quantum patents, Sinan Utku discusses the arguments both for and against the patent eligibility as an invention of entanglement swapping. The post Patenting Quantum Computing Innovations – Part 4: Entanglement Swapping appeared first on Quantum Computing Report .