Curator's Take
AI Commentary
This article demonstrates a concrete route to simulate non‑Hermitian Yang‑Lee criticality in an open quantum processor without the costly post‑selection step that has limited previous experiments. By engineering competing unitary and dissipative channels, the authors map the dynamics onto the exact Yang‑Lee transfer matrix, turning a purely theoretical construct into measurable spin correlations and Loschmidt‑echo observables on near‑term hardware. The approach not only broadens the toolbox for exploring exceptional points and complex‑field phase transitions but also offers a scalable template for embedding arbitrary non‑Hermitian Hamiltonians in Lindbladian evolution, paving the way for experimental studies of otherwise inaccessible quantum critical phenomena.
— Mark Eatherly
Summary
We show that the $d+0$-dimensional Yang-Lee theory describing classical Ising spins in an imaginary magnetic field can be realized, without post-selection, within a $(d-1)+1$ open quantum system whose dynamics consist of local unitaries and engineered dissipation. Competition between the coherent unitary and dissipative dynamics drives a transition wherein the time-dependence of a particular class of linear observables changes from damped oscillatory "underdamped" to purely exponential "overdamped" decay. Our construction relies on an extensive number of weak-symmetries of the Lindbladian fixed by the choice of observable but is otherwise exact. Consequently, we show that the dynamics are described by the non-Hermitian generator of the Yang-Lee transfer matrix, leading to an effective Yang-Lee theory defined on the spacetime history of the open system. By locally modifying the dynamics, we directly measure spin correlation functions of the Yang-Lee theory as well as a related "Loschmidt Echo" correlator which we detail. We explicitly show that the required dissipation channels can be obtained through local $2$-qubit gates and discuss potential realization on near-term quantum simulator devices. Finally, we generalize our construction to embed arbitrary non-Hermitian Hamiltonians within an open quantum system under Lindbladian time-evolution without post-selection, drawing connections between unconditional open quantum dynamics, exceptional point physics, and non-unitary statistical mechanics.