In briefExact analytical solution for collectively pumped superradiance in Dicke states
SummaryThis paper studies a group of N two-level emitters that decay collectively and are pumped collectively, staying within the symmetric Dicke states. The authors sum up the infinitely many quantum trajectories created by competing pumping and decay to obtain an exact finite continued fraction for the Dicke-state populations. They also give perturbative transient solutions for strong and weak pumping, along with relaxation eigenvalues and emission observables for balanced pumping and decay.
Avishi Poddar, Nico Ba{\ss}ler, Julian Lyne et al.
In briefOptimal quantum discrimination at Liouvillian exceptional points
SummaryThis paper examines whether exceptional points (EPs) in non-Hermitian systems help detect weak perturbations. In finite-dimensional Lindblad systems with a unique stationary state and nonzero relaxation gap, the authors show EPs give no fundamental advantage in how observation time scales with perturbation strength. However, by selecting perturbations that boost the quantum Fisher information rate, EPs can reach a set detection accuracy faster than a non-EP reference with the same decay rate. An optomechanical model illustrates detecting a weak force at an EP in less time.
In briefRepulsive Landau Interactions Between Fermi Polarons at Strong Coupling
SummaryThis paper studies mediated interactions between quasiparticles emerging from a Fermi sea, known as Fermi polarons, using zero-temperature quantum Monte Carlo methods. The main result is that the Landau interaction between polarons stays repulsive across all coupling strengths on the polaronic branch in the strongly interacting regime. The authors also compute the real-space interaction between static impurities, which shows RKKY-like behavior at weak coupling and matches the nonperturbative Born-Oppenheimer result at strong coupling.
Renato Pessoa, S. A. Vitiello, Luis A. Pe\~na Ardila
In briefDynamical quantum simulations used as testbeds for quantum information
SummaryThis paper shows that dynamical quantum simulations built to compute response functions prepare many-body states that carry information beyond their original observable. Using local-pulse protocols for Green functions in finite XX and XXX spin chains as a case study, the authors encode a classical bit via opposite source rotations and track how this record spreads across local subsystems and how readily different measurements access it. They find that fermionic covariance reconstructs the signed response in the XX chain, while simple spin measurements recover more local information in the XXX chain. The analysis is extended to Bell state recovery, quantum communication rates, and bipartite and multipartite entanglement.
Su Yeon Chang, Hailey S. Murray, Brian Barch et al.
In briefMeet-in-the-Middle Compilation of the [CNOT] Class with Fibonacci Anyons
SummaryThis paper studies how to compile two-qubit gates for Fibonacci anyons, where errors arise from leakage out of the computational subspace into a fifth fusion state. The authors build a GPU pipeline that searches braid group subsets for low-leakage representatives of the [CNOT] class, narrowing the search space to reach braid length L=72. They prove that leakage lies in Z[φ], that nonzero leakage has an exponential lower bound in braid length, and derive limit distribution laws.
In briefRecovering classical gauge geometry from quantum master constraints
SummaryThe paper asks how the degenerate directions of classical first-class constraints can be recovered when quantum theory is taken as fundamental and the constraints are imposed through a single positive master operator. For a nonnegative master function whose zero set is a Morse–Bott critical manifold, the image of the linearized Hamiltonian vector field is shown to be the symplectic orthogonal of the zero set, with coisotropy equivalent to the linearization having square zero. Three realizations are discussed, including the spectral bottom for quadratic masters and results for the non-Abelian SL(2,R) model.
In briefAdaptive Information Mining: Reaching the Quantum Limit of Super-Resolution Imaging
SummaryThis paper presents Adaptive Information Mining (AIM), a framework that achieves super-resolution by refining measurements of incoming photons in sequence. A reconfigurable imaging system reshapes its measurement responses to maximize Fisher information. When imaging point sources, the authors report estimation errors 2 to 5 times closer to the fundamental quantum limit than traditional direct imaging.
Seungman Choi, Peter Menart, Andrew Schramka et al.
In briefPaper on homodyne-based tracking and parameter estimation for quantum systems in squeezed thermal baths.
SummaryThe paper derives an alternative stochastic master equation for quantum systems continuously measured by homodyne detection in a squeezed-thermal environment. This form identifies two collapse operators for monitored and unmonitored channels and expresses state evolution through Kraus-like operators, aiding numerical methods and Cramér-Rao bound evaluation. For qubit frequency estimation, the authors compute the Fisher information of continuous homodyne monitoring and find that its steady-state rate still scales exponentially with squeezing at nonzero temperature.
Eoin O'Connor, Francesco Albarelli, Marco G. Genoni
