Many-body physics with individually controlled Rydberg atoms

Abstract

Over the last decade, systems of individually-controlled neutral atoms, interacting with each other when excited to Rydberg states, have emerged as a promising platform for quantum simulation of many-body problems, in particular spin systems. Here, we review the techniques underlying quantum gas microscopes and arrays of optical tweezers used in these experiments, explain how the different types of interactions between Rydberg atoms allow a natural mapping onto various quantum spin models, and describe recent results that were obtained with this platform to study quantum many-body physics. I. MANY-BODY PHYSICS WITH SYNTHETIC MATTERMany-body physics is the field that studies the behavior of ensembles of interacting quantum particles. This is a broad area encompassing almost all condensed matter physics, but also nuclear and high-energy physics. Despite the immense successes obtained over the last decades, many phenomena observed experimentally still do not have a fully satisfactory explanation. At the origin of the difficulty lies the exponential scaling of the size of the Hilbert space with the number of interacting particles. In practice, the best known ab-initio methods allow calculating the evolution of less than 50 particles. To investigate relevant questions involving a much larger number of particles (after all even 1 mg of usual matter contains already 10 18 atoms!), one must rely on approximations, and the art of solving the many-body problem largely relies on mastering them. However, using approximations is not always possible and it may be hard to assess their range of validity. One approach to move forward was suggested by Richard Feynman [1] and consists in building a synthetic quantum system in the lab, implementing a model of interest for which no other way to solve it is known. The model may be an approximate description of a real material, but it can also be a purely abstract one. In this case, its implementation leads to the construction of an artificial many-body system, which becomes an object of study in its own. One appealing feature of this approach is the ability to vary the parameters of the model in ranges inaccessible otherwise, thus providing a way to better understand their respective influence. For example, if one is interested in the influence of interatomic interactions on the phase of a given system, synthetic systems become interesting as they allow varying their strength in a way which is usually impossible in real materials. The approach introduced by Feynman is usually referred to as quantum simulation [2, 3], but it can be viewed more generally as exploring many-body physics with synthetic systems: in the same way chemists design new materials exhibiting interesting properties (such as magnetism, superconductivity. . . ), physicists assemble artificial systems and study their properties, with the hope to observe new phenomena.For a long time, this idea remained theoretical as the experimental control over quantum objects was not advanced enough. The situation changed radically...

Giant Rydberg Excitons in Synthetic and Artificial Cuprous Oxide

“…The emerging research field of Rydberg excitons in cuprous oxide is facilitating an exciting crossover between two previously siloed disciplines: cold-atom physics and semiconductor quantum optics. The coherent spectroscopy of Rydberg states in gas-phase atomic systems has garnered great recent interest, with applications in the measurement of electromagnetic fields from DC to terahertz frequencies [1,2], quantum simulation [3] and computation [4], and quantum optics [5]. There is clear interest in observing similar states in semiconductor systems, where half a century of development in state-of-theart nano-fabrication techniques provide capabilities that go way beyond those available in the gas phase.…”

Quantum computing with neutral atoms

“…Each qubit of the register then behaves as a spin whose states are |↓ = |0 and |↑ = |1 . Depending on the Rydberg states that are involved in the process, the spins experience different types of interactions that translate into different Hamiltonians [6]. The most studied one is the Ising model, which is obtained when the |↓ state is one of the ground states and the |↑ a Rydberg state [25,26,27,28].…”

“…Fundamental research on quantum information processing platforms using neutral atoms has been going on for years, and has led to impressive scientific results such as the simulation of highly complex quantum systems well above 100 qubits, beyond the reach of classical high performance computers [6]. Only recently did it become possible to contemplate manufacturing devices for commercial use thanks to continuous progress in design and engineering.…”

Precise programmable quantum simulations with optical lattices

“…Here, we consider integration of the recently developed DMD techniques in controlling optical potentials 13,[35][36][37][38] to optical lattices, and calibrate the platform towards precise programmable quantum simulations. We develop an efficient algorithm, which can systematically construct an inhomogeneous optical potential to precisely simulate a given tight binding lattice model, i.e., both the onsite energies and the tunnelings are made precisely programmable.…”