We introduce a Ramsey pulse scheme which extracts the non-Hermitian Hamiltonian associated with an arbitrary Lindblad dynamics. We propose a related protocol to measure via interferometry a generalized Loschmidt echo of a generic state evolving in time with the non-Hermitian Hamiltonian itself, and we apply the scheme to a one-dimensional weakly interacting Bose gas coupled to a stochastic atomic impurity. The Loschmidt echo is mapped into a functional integral from which we calculate the long-time decohering dynamics at arbitrary impurity strengths. For strong dissipation we uncover the phenomenology of a quantum many-body Zeno effect: Corrections to the decoherence exponent resulting from the impurity self-energy become purely imaginary, in contrast to the regime of small dissipation where they instead enhance the decay of quantum coherences. Our results illustrate the prospects for experiments employing Ramsey interferometry to study dissipative quantum impurities in condensed matter and cold-atom systems.

中文翻译：

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非Hermitian量子杂质的Ramsey干涉测量

我们引入了一种拉姆西脉冲方案，该方案提取与任意Lindblad动力学相关的非埃尔米特哈密顿量。我们提出了一种相关的协议，通过干涉测量法来测量随非赫米特哈密顿量本身随时间演化的一般状态的广义Loschmidt回波，并将该方案应用于耦合到随机原子杂质的一维弱相互作用的玻色气体。Loschmidt回波被映射到一个函数积分中，从中我们可以计算出任意杂质强度下的长时间去相干动力学。对于强耗散，我们揭示了量子多体芝诺效应的现象学：与杂质的小耗散状态相反，它们纠正了量子相干的衰变，而杂质自能量导致的退相干指数的校正变得纯粹是虚构的。