Locality is a transversal principle that governs quantum dynamics of many-body systems. However, for cavity-embedded systems, such a fundamental notion is hindered by the presence of nonlocal cavity modes, leaving space for new possible dynamical behavior. Here, we investigate the real-time dynamics of low-energy excitations in one-dimensional Rydberg atom arrays coupled to a global cavity mode. We derive an effective description in terms of a Tavis-Cummings-Ising model, whose phase diagram features ordered and disordered phases. The nonlocal nature of the cavity mode drastically affects the emergent meson and string dynamics. Mesons hybridize coherently with the cavity photons, leading to composite meson-polariton excitations. Strings, differently from local interacting theories, acquire a finite kinetic energy thanks to nonlocal cavity-mediated interactions between the underlying domain walls. We then conclude by presenting a new concrete experimental blueprint for a cavity QED Rydberg atom array simulator where the physics outlined in this Letter can be realized.
Locality is a transversal principle that governs quantum dynamics of many-body systems. However, for cavity-embedded systems, such a fundamental notion is hindered by the presence of nonlocal cavity modes, leaving space for new possible dynamical behavior. Here, we investigate the real-time dynamics of low-energy excitations in one-dimensional Rydberg atom arrays coupled to a global cavity mode. We derive an effective description in terms of a Tavis-Cummings-Ising model, whose phase diagram features ordered and disordered phases. The nonlocal nature of the cavity mode drastically affects the emergent meson and string dynamics. Mesons hybridize coherently with the cavity photons, leading to composite meson-polariton excitations. Strings, differently from local interacting theories, acquire a finite kinetic energy thanks to nonlocal cavity-mediated interactions between the underlying domain walls. We then conclude by presenting a new concrete experimental blueprint for a cavity QED Rydberg atom array simulator where the physics outlined in this Letter can be realized.
Rydberg atom triangular arrays in an optical cavity serve as an ideal platform for understanding the interplay between geometric frustration and quantized photons. Using a large-scale quantum Monte Carlo method, we obtain a rich ground state phase diagram. Around half-filling, the infinite long-range light-matter interaction lifts the ground state degeneracy, resulting in a novel order-coexisted superradiant clock phase that completely destroys the fragile order-by-disorder phase observed in classical light fields. According to the Ginzburg-Landau theory, this replacement may result from the competition between threefold and sixfold clock terms. Similar to the spin supersolid, the clear first-order phase transition at the Z_{2} symmetry line is attributed to the nonzero photon density, which couples to the threefold clock term. Finally, we discuss the low-energy physics in the dimer language and propose that cavity-mediated nonlocal ring exchange interactions may play a critical role in the rich physics induced by the attachment of cavity QED. Our Letter opens a new arena of research on the emergent phenomena of quantum phase transitions in many-body quantum optics.
Confinement is a pivotal phenomenon in numerous models of high-energy and statistical physics. In this study, we investigate the emergence of confined meson excitations within a one-dimensional system, comprising Rydberg-dressed atoms trapped and coupled to a cavity field. This system can be effectively represented by an Ising-Dicke Hamiltonian model. The observed ground-state phase diagram reveals a first-order transition from a ferromagnetic-subradiant phase to a paramagnetic-superradiant phase. Notably, a quench near the transition point within the ferromagnetic-subradiant phase induces meson oscillations in the spins and leads to the creation of squeezed-vacuum light states. We suggest a method for the photonic characterization of these confined excitations, utilizing homodyne detection and single-site imaging techniques to observe the localized particles. The methodologies and results detailed in this Letter are feasible for implementation on existing cavity-QED platforms, employing Rydberg-atom arrays in deep optical lattices or optical tweezers.
Rydberg atom arrays with van der Waals interactions provide a controllable path to quantum simulate the locally connected transverse-field Ising model (TFIM), a prototypical model in statistical mechanics. Remotely operating the publicly accessible Aquila Rydberg atom array, we experimentally investigate the physics of TFIM far from equilibrium and uncover significant deviations from the theoretical predictions. Rather than the expected ballistic spread of correlations, the Rydberg simulator exhibits a sub-ballistic spread, along with a logarithmic scaling of entanglement entropy in time all while the system mostly retains its initial magnetization. By modeling the atom motion, we trace these effects to an emergent disorder in Rydberg atom arrays, which we characterize with a minimal random spin model. We further experimentally explore the different dynamical regimes hosted in the system by varying the lattice spacing and the Rabi frequency. Our findings highlight the crucial role of atom motion in the many-body dynamics of Rydberg atom arrays at the TFIM limit, and propose simple benchmark measurements to test for its presence in future experiments.
Scalable quantum computers and quantum networks require the combination of quantum processing nodes with efficient light-matter interfaces to distribute quantum information in local or long-distance quantum networks. Neutral-atom arrays have both been coupled to Rydberg states to enable high-fidelity quantum gates in universal processing architectures, and to optical cavities to realize interfaces to photons. However, combining these two capabilities and coupling atom arrays to highly excited Rydberg states in the mode of an optical cavity has been an outstanding challenge. Here we present a novel cavity-coupled Rydberg array that achieves this long-standing goal. We prepare, detect, and control individual atoms in a scalable optical tweezer array, couple them strongly to the optical mode of a high-finesse optical cavity and excite them in a controlled way to Rydberg states. We show that high-cooperativity coupling to an optical cavity -- demonstrated via the dispersive shift of the resonance of the cavity in presence of the atoms -- and strong Rydberg interactions -- demonstrated via the collective enhancement of Rydberg coupling in the atomic array -- can be achieved in our setup at the same spatial location. Our presented experimental platform opens the path to several new directions, including the realization of quantum network nodes, quantum simulation of long-range interacting, open quantum systems and photonic-state engineering leveraging high-fidelity Rydberg control.
Abstract Photonic materials are an emerging platform to explore quantum matter (Carusotto and Ciuti 2013 Rev. Mod. Phys. 85 299; Sommer et al 2015 arXiv: 1506.00341 ) and quantum dynamics (Peyronel et al 2012 Nature 488 57). The development of Rydberg electromagnetically induced transparency (Weatherill et al 2008 J. Phys. B: At. Mol. Opt. Phys. 41 201002; Petrosyan et al 2011 Phys. Rev. Lett. 107 213601) provided a clear route to strong interactions between individual optical photons. In conjunction with carefully designed optical resonators, it is now possible to achieve extraordinary control of the properties of individual photons, introducing tunable gauge fields (Schine et al 2016 Nature 534 671) whilst imbuing the photons with mass and embedding them on curved spatial manifolds (Sommer et al 2016 New J. Phys. 18 035008). Building on work formalizing Rydberg mediated interactions between propagating photons (Gorshkov et al 2011 Phys. Rev. Lett. 107 133602; Gullans et al 2016 Phys. Rev. Lett. 117 113601), we develop a theory of interacting Rydberg polaritons in multimode optical resonators, where the strong interactions are married with tunable single particle properties to build and probe exotic matter. In the presence of strong coupling between the resonator field and a Rydberg-dressed atomic ensemble, a quasiparticle called the ‘cavity Rydberg polariton’ emerges. We investigate its properties, finding that it inherits both the fast dynamics of its photonic constituents and the strong interactions of its atomic constituents. We develop tools to properly renormalize the interactions when polaritons approach each other, and investigate the impact of atomic motion on the coherence of multi-mode polaritons, showing that most channels for atom-polariton cross-thermalization are strongly suppressed. Finally, we propose to harness the repeated diffraction and refocusing of the optical resonator to realize interactions which are local in momentum-space. This work points the way to efficient modeling of polaritonic quantum materials in properly renormalized strongly interacting effective theories, thereby enabling experimental studies of photonic fractional quantum Hall fluids and crystals (Sommer et al 2015 arXiv: 1506.00341 ; Umucalılar et al 2014 Phys. Rev. A 89 023803; Grusdt and Fleischhauer 2013 Phys. Rev. A 87 043628), plus photonic quantum information processors and repeaters (Jaksch et al 2000 Phys. Rev. Lett. 85 2208; Saffman et al 2010 Rev. Mod. Phys. 82 2313; Han et al 2010 Phys. Rev. A 81 , 052311).
An exciting frontier in quantum information science is the creation and manipulation of \nbottom-up quantum systems that are built and controlled one by one. For the past 30 \nyears, we have witnessed signi cant progresses in harnessing strong atom- eld interactions \nfor critical applications in quantum computation, communication, simulation, and metrology. \nBy extension, we can envisage a quantum network consisting of material nodes coupled \ntogether with in nite-dimensional bosonic quantum channels. In this context, there \nhas been active research worldwide to achieve quantum optical circuits, for which single \natoms are wired by freely-propagating single photons through the circuit elements. For all \nthese systems, the system-size expansion with atoms and photons results in a fundamental \npathologic scaling that linearizes the very atom- eld interaction, and signi cantly limits \nthe degree of non-classicality and entanglement in analog atom- eld quantum systems for \natom number N 1. \nThe long-term motivation of this MSc thesis is (i) to discover new physical mechanisms \nthat extend the inherent scaling behavior of atom- eld interactions and (ii) to \ndevelop quantum optics toolkits that design dynamical gauge structures for the realization \nof lattice-gauge-theoretic quantum network and the synthesis of novel quantum optically \ngauged materials. The basic premise is to achieve the strong coupling regime for a quantum \nmany-body material system interacting with the quantized elds of an optical cavity. Our \nlaboratory e ort can be described as the march towards \\many-body QED," where optical \n elds acquire some properties of the material interactions that constrain their dynamical \nprocesses, as with quantum eld theories. While such an e ort currently do not exist elsewhere, \nwe are convicted that our work will become an essential endeavor to enable cavity \nquantum electrodynamics (QED) in the bona- de regime of quantum many-body physics \nin this entanglement frontier. \nIn this context, I describe an example in Chapter 2 that utilizes strong RydbergRydberg \ninteractions to design dynamical gauge structures for the quantum square ice \nmodels. Quantum \nuctuations driven by cavity-mediated in nite-range interaction stabilize \nthe quantum-gauged system into a long-range entangled quantum spin liquid that may \nbe detected through the time-ordered photoelectric statistics for photons leaking out of the \ncavity. Fractionalized \\spinon" and \\vison" excitations can be manipulated for topological \nquantum computation, and the emergent photons of arti cial QED in our lattice gauge \ntheoretic system can be directly measured and studied. \nThe laboratory challenge towards strongly coupled cavity Rydberg polaritons encompasses \nthree daunting research milestones that push the technological boundaries beyond of the state-of-the-arts. In Chapter 3, I discuss our extreme-high-vacuum chamber (XHV) \ncluster system that allows the world's lowest operating vacuum environment P ' 10 \nTorr for an ultracold AMO experiment with long background-limited trap lifetimes. In \nChapter 4, I discuss our ultrastable laser systems stabilized to the ultra-low-expansion \noptical cavities. Coupled with a scalable eld-programmable-gate-array (FPGA) digitalanalog \ncontrol system, we can manipulate arbitrarily the phase-amplitude relationship of \nseveral dozens of laser elds across 300 nm to 1550 nm at mHz precision. In Chapter 5, \nwe discuss the quantum trajectory simulations for manipulating the external degrees of \nfreedom of ultracold atoms with external laser elds. Electrically tunable liquid crystal \nlens creates a dynamically tunable optical trap to move the ultracold atomic gases over \nlong distance within the ultra-high-vacuum (UHV) chamber system. \nIn Chapter 6, I discuss our collaborative development of two science cavity platforms \n{ the \\Rydberg" quantum dot and the many-body QED platforms. An important development \nwas the research into new high-index IBS materials, where we have utilized our \nlow-loss optical mirrors for extending the world's highest cavity nesse F 500k! We discuss \nthe unique challenges of implementing optical cavity QED for Rydberg atoms, which \nrequired tremendous degrees of electromagnetic shielding and eld control. Single-crystal \nSapphire structure, along with Angstrom-level diamond-turned Ti blade electrodes, is utilized \nfor the eld compensation and extinction by > 60 dB. Single-crystal PZTs on silica \nV-grooves are utilized for the stabilization of the optical cavity with length uncertainty less \nthan 1=100 of a single nucleon, along with extreme level of vibration isolation in a XHV \nenvironment. The capability to perform in-situ RF plasma cleaning allows the regeneration \nof optical mirrors when coated with a few Cs atoms. Lastly but not the least, we combine \nsingle-atom resolution quantum gas microscopy technique with superpixel holographic algorithm \nto project arbitrary real-time recon gurable di raction-limited optical potential \nlandscapes for the preparation of low-entropy atom arrays.