Particles subject to confinement experience an attractive potential that increases without bound as they separate. A prominent example is colour confinement in particle physics, in which baryons and mesons are produced by quark confinement. Confinement can also occur in low-energy quantum many-body systems when elementary excitations are confined into bound quasiparticles. Here we report the observation of magnetic domain-wall confinement in interacting spin chains with a trapped-ion quantum simulator. By measuring how correlations spread, we show that confinement can suppress information propagation and thermalization in such many-body systems. We quantitatively determine the excitation energy of domain-wall bound states from the non-equilibrium quench dynamics. We also study the number of domain-wall excitations created for different quench parameters, in a regime that is difficult to model with classical computers. This work demonstrates the capability of quantum simulators for investigating high-energy physics phenomena, such as quark collision and string breaking. Long-range Ising interactions present in one-dimensional spin chains can induce a confining potential between pairs of domain walls, slowing down the thermalization of the system. This has now been observed in a trapped-ion quantum simulator.

}, issn = {1745-2473}, doi = {10.1038/s41567-021-01194-3}, author = {Tan, W. L. and Becker, P. and Liu, F. and Pagano, G. and Collins, K. S. and De, A. and Feng, L. and Kaplan, H. B. and Kyprianidis, A. and Lundgren, R. and Morong, W. and Whitsitt, S. and Gorshkov, A. V. and Monroe, C.} } @article { WOS:000662088000025, title = {Observation of a prethermal discrete time crystal}, journal = {Science}, volume = {372}, number = {6547}, year = {2021}, month = {JUN 11}, pages = {1192+}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, type = {Article}, abstract = {Extending the framework of statistical physics to the nonequilibrium setting has led to the discovery of previously unidentified phases of matter, often catalyzed by periodic driving. However, preventing the runaway heating that is associated with driving a strongly interacting quantum system remains a challenge in the investigation of these newly discovered phases. In this work, we utilize a trapped-ion quantum simulator to observe the signatures of a nonequilibrium driven phase without disorder-the prethermal discrete time crystal. Here, the heating problem is circumvented not by disorder-induced many-body localization, but rather by high-frequency driving, which leads to an expansive time window where nonequilibrium phases can emerge. Floquet prethermalization is thus presented as a general strategy for creating, stabilizing, and studying intrinsically out-of-equilibrium phases of matter.}, issn = {0036-8075}, doi = {10.1126/science.abg8102}, author = {Kyprianidis, A. and Machado, F. and Morong, W. and Becker, P. and Collins, K. S. and Else, V, D. and Feng, L. and Hess, P. W. and Nayak, C. and Pagano, G. and Yao, N. Y. and Monroe, C.} } @article {21526, title = {Observation of {Stark} many-body localization without disorder}, journal = {Nature}, volume = {599}, year = {2021}, pages = {393{\textendash}398}, abstract = {Thermalization is a ubiquitous process of statistical physics, in which a physical system reaches an equilibrium state that is defined by a few global properties such as temperature. Even in isolated quantum many-body systems, limited to reversible dynamics, thermalization typically prevails1. However, in these systems, there is another possibility: many-body localization (MBL) can result in preservation of a non-thermal state2,3. While disorder has long been considered an essential ingredient for this phenomenon, recent theoretical work has suggested that a quantum many-body system with a spatially increasing field{\textemdash}but no disorder{\textemdash}can also exhibit MBL4, resulting in {\textquoteleft}Stark MBL{\textquoteright}5. Here we realize Stark MBL in a trapped-ion quantum simulator and demonstrate its key properties: halting of thermalization and slow propagation of correlations. Tailoring the interactions between ionic spins in an effective field gradient, we directly observe their microscopic equilibration for a variety of initial states, and we apply single-site control to measure correlations between separate regions of the spin chain. Furthermore, by engineering a varying gradient, we create a disorder-free system with coexisting long-lived thermalized and non-thermal regions. The results demonstrate the unexpected generality of MBL, with implications about the fundamental requirements for thermalization and with potential uses in engineering long-lived non-equilibrium quantum matter.

}, issn = {1476-4687}, doi = {10.1038/s41586-021-03988-0}, url = {https://doi.org/10.1038/s41586-021-03988-0}, author = {Morong, W. and Liu, F. and Becker, P. and Collins, K. S. and Feng, L. and Kyprianidis, A. and Pagano, G. and You, T. and Gorshkov, A. V. and Monroe, C.} } @article { WOS:000655978400001, title = {Programmable quantum simulations of spin systems with trapped ions}, journal = {Rev. Mod. Phys.}, volume = {93}, number = {2}, year = {2021}, month = {APR 7}, publisher = {AMER PHYSICAL SOC}, type = {Review}, abstract = {Laser-cooled and trapped atomic ions form an ideal standard for the simulation of interacting quantum spin models. Effective spins are represented by appropriate internal energy levels within each ion, and the spins can be measured with near-perfect efficiency using state-dependent fluorescence techniques. By applying optical fields that exert optical dipole forces on the ions, their Coulomb interaction can be modulated to produce long-range and tunable spin-spin interactions that can be reconfigured by shaping the spectrum and pattern of the laser fields in a prototypical example of a quantum simulator. Here the theoretical mapping of atomic ions to interacting spin systems, the preparation of complex equilibrium states, and the study of dynamical processes in these many-body interacting quantum systems are reviewed, and the use of this platform for optimization and other tasks is discussed. The use of such quantum simulators for studying spin models may inform our understanding of exotic quantum materials and shed light on the behavior of interacting quantum systems that cannot be modeled with conventional computers.}, issn = {0034-6861}, doi = {10.1103/RevModPhys.93.025001}, author = {Monroe, C. and Campbell, W. C. and Duan, L-M and Gong, Z-X and Gorshkov, V, A. and Hess, P. W. and Islam, R. and Kim, K. and Linke, N. M. and Pagano, G. and Richerme, P. and Senko, C. and Yao, N. Y.} } @article { ISI:000553250400007, title = {Efficient Ground-State Cooling of Large Trapped-Ion Chains with an Electromagnetically-Induced-Transparency Tripod Scheme}, journal = {Phys. Rev. Lett.}, volume = {125}, number = {5}, year = {2020}, month = {JUL 29}, pages = {053001}, publisher = {AMER PHYSICAL SOC}, type = {Article}, abstract = {We report the electromagnetically-induced-transparency (EIT) cooling of a large trapped Yb-171(+) ion chain to the quantum ground state. Unlike conventional EIT cooling, we engage a four-level tripod structure and achieve fast sub-Doppler cooling over all motional modes. We observe simultaneous groundstate cooling across the complete transverse mode spectrum of up to 40 ions, occupying a bandwidth of over 3 MHz. The cooling time is observed to be less than 300 mu s, independent of the number of ions. Such efficient cooling across the entire spectrum is essential for high-fidelity quantum operations using trapped ion crystals for quantum simulators or quantum computers.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.125.053001}, author = {Feng, L. and Tan, W. L. and De, A. and Menon, A. and Chu, A. and Pagano, G. and Monroe, C.} } @article { ISI:000447062400001, title = {Cryogenic trapped-ion system for large scale quantum simulation}, journal = {QUANTUM SCIENCE AND TECHNOLOGY}, volume = {4}, number = {1}, year = {2019}, month = {JAN}, pages = {UNSP 014004}, issn = {2058-9565}, doi = {10.1088/2058-9565/aae0fe}, author = {Pagano, G. and Hess, P. W. and Kaplan, H. B. and Tan, W. L. and Richerme, P. and Becker, P. and Kyprianidis, A. and Zhang, J. and Birckelbaw, E. and Hernandez, M. R. and Wu, Y. and Monroe, C.} } @article { ISI:000413927000009, title = {Non-thermalization in trapped atomic ion spin chains}, journal = {PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES}, volume = {375}, number = {2108}, year = {2017}, month = {DEC 13}, issn = {1364-503X}, doi = {10.1098/rsta.2017.0107}, author = {Hess, P. W. and Becker, P. and Kaplan, H. B. and Kyprianidis, A. and Lee, A. C. and Neyenhuis, B. and Pagano, G. and Richerme, P. and Senko, C. and Smith, J. and Tan, W. L. and Zhang, J. and Monroe, C.} }