Quantum Journal

Counterdiabatic Quantum Circuits

Counterdiabatic driving provides a universal route to fast quantum control, but its standard formulation presupposes a Hamiltonian generator. We develop a Hamiltonian-free theory of the adiabatic gauge potential (AGP) for parameter-dependent unitary operators $U_\lambda$. Exact and regularized versions of the AGP follow from a Hermitian, banded linear system at a cost comparable to the Lanczos construction in the Hermitian case, requiring neithe...

Gap-Protected Heisenberg-Limited Squeezing with Locally Interacting Multi-Level Spins

We demonstrate a general mechanism to generate scalable, metrologically useful entanglement in the form of generalized spin squeezing in multi-level (qudit) spin systems with power-law interactions. We demonstrate this for spin-changing dynamics, extending the physics of spin-nematic squeezing known from spinor BECs to spatially extended lattice geometries. In the absence of all-to-all connectivity, the dynamics generally suffers from leakage in...

Researchers Learn Quantum Systems Using Unstable States - Quantum Zeitgeist

Researchers Find Gaussian States Yield Unique Quantum Transport Barycentres

Until now, determining whether combinations of quantum states would themselves remain predictably Gaussian has remained an open problem. This work demonstrates that providing even one ‘faithful’ Gaussian input guarantees both a uniquely defined and entirely Gaussian resulting barycenter, a result previously unproven. Furthermore, it establishes how these quantum solutions converge towards their classical counterparts in transport theory.