We propose an analogue quantum simulator of a 1 + 1D spacetime containing non-causal curves, in particular null geodesics going back in time, by means of a dc-SQUID array embedded on an open superconducting transmission line. This is achieved by mimicking the spatial dependence of the metric with the propagation speed of the electromagnetic field in the simulator, which can be modulated by an external magnetic flux. We show that it is possible to simulate a spacetime region containing non-causal null geodesics, but not a full spacetime containing a chronological horizon separating regions with non-causal null geodesics and regions without them. This is in agreement with a recent suggestion of an analogue-gravity chronology protection mechanism by Barceló et al.

中文翻译：

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dc-SQUID 阵列中的模拟非因果零曲线和时序保护

我们通过嵌入在开放超导传输线上的 dc-SQUID 阵列，提出了一个包含非因果曲线的 1 + 1D 时空模拟量子模拟器，特别​​是回溯到时间的零测地线。这是通过在模拟器中模拟度量与电磁场传播速度的空间依赖性来实现的，该传播速度可以通过外部磁通量进行调制。我们表明，可以模拟包含非因果零测地线的时空区域，但不能模拟包含按时间顺序划分具有非因果零测地线区域和没有它们的区域的时间层的完整时空。这与 Barceló 等人最近提出的模拟重力年表保护机制的建议一致。