Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.
Realizing robust quantum phenomena in strongly interacting systems is one of the central challenges in modern physical science. Approaches ranging from topological protection to quantum error correction are currently being explored across many different experimental platforms, including electrons in condensed-matter systems, trapped atoms and photons. Although photon-photon interactions are typically negligible in conventional optical media, strong interactions between individual photons have recently been engineered in several systems. Here, using coherent coupling between light and Rydberg excitations in an ultracold atomic gas, we demonstrate a controlled and coherent exchange collision between two photons that is accompanied by a π/2 phase shift. The effect is robust in that the value of the phase shift is determined by the interaction symmetry rather than the precise experimental parameters, and in that it occurs under conditions where photon absorption is minimal. The measured phase shift of 0.48(3)π is in excellent agreement with a theoretical model. These observations open a route to realizing robust single-photon switches and all-optical quantum logic gates, and to exploring novel quantum many-body phenomena with strongly interacting photons.
We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within 3 μs with a success probability of F p ¼ 0.93 AE 0.02, rotate it, and read out its state in 6 μs with a single-shot fidelity of F d ¼ 0.92 AE 0.04. The ensemble-assisted detection is 10 3 times faster than imaging of a single atom with the same optical resolution, and enables fast repeated nondestructive measurement. We observe qubit coherence times of 15 μs, much longer than the π rotation time of 90 ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.
Contents I. Methods 1 A. Atom preparation 1 B. Correlation measurements 2 II. A two-component effective equation governing polariton dynamics 2 A. Single-particle dynamics 3 B. Two-particle dynamics 4 C. Comparing full theory with two-component effective theory 7
Neutral atom arrays recently emerged as one the leading platforms for large-scale quantum computing and simulations [1, 2]. These systems offer a variety of possible qubit encodings with long coherence times along with exceptional programmability and reconfigurability of the array geometry and qubit connectivity. In addition, strong, highly coherent coupling between the qubits can be achieved using Rydberg states of the atoms. QuEra provides a cloud-accessible, programmable 256-qubit quantum simulator based on a two-dimensional array of Rubidium-87 atoms in reconfigurable optical tweezers.
We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within 3 μs with a success probability of F p ¼ 0.93 AE 0.02, rotate it, and read out its state in 6 μs with a single-shot fidelity of F d ¼ 0.92 AE 0.04. The ensemble-assisted detection is 10 3 times faster than imaging of a single atom with the same optical resolution, and enables fast repeated nondestructive measurement. We observe qubit coherence times of 15 μs, much longer than the π rotation time of 90 ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.
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