Quantum Zeno effects across a parity-time symmetry breaking transition in atomic momentum space

We experimentally study quantum Zeno effects in a parity-time (PT) symmetric cold atom gas periodically coupled to reservoir. Based on the state-of-the-art control of inter-site couplings atoms momentum lattice, we implement synthetic two-level system with passive PT symmetry over two lattice sites, where an effective dissipation is introduced through repeated rest lattice. Quantum (anti-Zeno) manifest our experiment as overall becoming suppressed (enhanced) increasing coupling intensity or frequency. demonstrate that regimes exist broken phase, and are bounded by exceptional points separating phases, well discrete set critical frequencies. Our establishes connection between PT-symmetry-breaking transitions effects, extendable higher dimensions interacting regimes, thanks flexible