A new preprint lays out a way to study Yang-Lee criticality through an open quantum system whose motion combines ordinary unitary evolution with dissipation. Its central claim is a formally exact mapping: in a carefully selected observable sector, the system’s Lindbladian—the operator describing that combined evolution—reproduces the target non-Hermitian dynamics without post-selection, the practice of discarding unwanted experimental outcomes.
The manuscript, identified as arXiv:2608.26082v1, is a preprint dated 26 August 2026, and the work presents a theoretical construction rather than a reported device demonstration. Its numerical illustration compares qubit-chain sizes L = 4, 5, 6 and 7, giving a small finite-size window rather than a large-system test.
The mapping lives in a narrow sector
To make the mapping work, the authors isolate a non-Hermitian sector called Lambda. It is spanned by Pauli strings that place an X or Y operator on every site. Observables chosen inside that sector are governed by the Lindbladian after it is projected into the sector, rather than by the full open-system evolution. That projection is what allows a non-Hermitian description to appear at the level of selected observables.
Within this construction, the expectation value of the selected observables is identified with the Yang-Lee partition function defined on the open system’s spacetime history. In plain terms, a quantity obtained from the evolving open system is used as the counterpart of the partition function, without requiring post-selected trajectories. The correspondence depends on choosing the specified observable sector and boundary construction, so it is not a claim about every measurement of the system.
What the finite simulations showed
The numerical test used a Suzuki-Trotter approximation, a step-by-step digital version of continuous Lindbladian evolution. The reported discretization error is O(delta t^2), meaning the approximation becomes more accurate as the time step is reduced. The illustration compared qubit-chain sizes L = 4, 5, 6 and 7, giving a small finite-size window rather than a large-system test.
The clearest signal appeared in the time dependence of a selected observable. As the model parameter theta increased, its behavior moved from overdamped—motion that dies away without visible oscillation—to underdamped behavior, with an apparent threshold theta_c of about 0.64. The threshold was a numerical model result, not a statistical estimate with an uncertainty interval.
Other diagnostics pointed in different directions. At the reported critical point, the Yang-Lee spin-spin correlator rose with the separation between sites and exceeded 1. Its growth was qualitatively consistent with a power-law form proportional to |i-j|^(4/5), but the calculation did not match that prediction quantitatively; the authors attribute the gap to finite-size effects.
By contrast, the Loschmidt Echo correlator, written as LE(2), decreased with separation and was described as bounded above by 1. That contrast does not settle the broader theory: the authors identify a theoretical understanding of the expected Loschmidt Echo scaling as an open problem.
From a model to a proposal
The paper then extends the idea beyond the Yang-Lee example. The authors state that any target non-Hermitian Hamiltonian can be represented by a Lindbladian whose projection into an associated non-Hermitian subspace is equivalent to that target. The general construction assumes a tensor-product Hilbert-space structure and finite-dimensional local sites, so its reach is tied to those structural conditions.
For a local site with Hilbert-space dimension d, the proposed construction introduces n = ceil(log2 d) qubits and an additional four-dimensional auxiliary qudit. The implementation is digital, using nearest-neighbor gates, ancilla-engineered dissipation, and CNOT or CZ as the stated two-qubit gate types. This is a resource prescription, not performance data from a working device.
Several obstacles remain before the proposal could be judged as a practical simulation method. The formal projection requires a nonlocal observable, while estimating the partition-function quantity is stated to require exponentially many experimental runs in practice. Finite Suzuki-Trotter steps also introduce the reported O(delta t^2) error, and the general jump-operator construction is not necessarily the most efficient or physically natural representation.
For now, the paper’s contribution is a mathematical and numerical framework linking an open-system observable to Yang-Lee dynamics. It does not establish quantitative conformal scaling in the finite systems studied, practical sample efficiency for partition-function estimation, or an efficient and physically natural realization for arbitrary target Hamiltonians. Experimental tests on quantum simulators, along with work on higher-dimensional extensions and ways to remove the nonlocal-readout and sampling burdens, are left for future research.
Paper data and sources
Original title: Yang-Lee Criticality as a Dissipative Dynamical Phase Transition: Quantum Simulation of non-Hermitian Physics without Post-selection
Authors: Stephen W. Yan
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text