"Robust continuous time crystal in an electron–nuclear spin system" (2024) <a href="https://www.nature.com/articles/s41567-023-02351-6" rel="nofollow">https://www.nature.com/articles/s41567-023-02351-6</a> :<p>> <i>The time crystal state enables fundamental studies of nonlinear interactions and has potential applications as a precise on-chip frequency standard.</i><p>Re: Retrocausality:
<a href="https://news.ycombinator.com/item?id=38047149">https://news.ycombinator.com/item?id=38047149</a><p>Does retrocausality of time crystals affect quantum circuit measurement at t>0?<p>"Double-slit time diffraction at optical frequencies" (2023), "Incandescent Temporal Metamaterials" (2023) <a href="https://news.ycombinator.com/item?id=39162149">https://news.ycombinator.com/item?id=39162149</a><p>(Edit) /? Indefinite causal order: <a href="https://www.google.com/search?q=indefinite+causal+order" rel="nofollow">https://www.google.com/search?q=indefinite+causal+order</a><p>"Admissible causal structures and correlations" (
<a href="https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.4.040307" rel="nofollow">https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuan...</a>