[Paper Review] Finite-range interacting Ising quantum magnets with Rydberg atoms in optical lattices - From Rydberg superatoms to crystallization

Peter Schauß|arXiv (Cornell University)|Jun 27, 2017

Cold Atom Physics and Bose-Einstein CondensatesPhysics and Astronomy168 references18 citations

TL;DR

This paper reviews the realization of finite-range interacting Ising quantum magnets using Rydberg atoms in optical lattices, demonstrating tunable long-range interactions via $1/r^6$ van der Waals forces. It details experimental progress from the superatom regime—where only one excitation exists due to blockade—to the observation of spin crystallization in larger systems, enabled by site-resolved detection and controlled transverse and longitudinal fields.

ABSTRACT

Finite-range interacting spin models are the simplest models to study the effect of beyond nearest-neighbour interactions and access new effects caused by the range of the interactions. Recent experiments have reached the regime of dominant interactions in Ising quantum magnets via optical coupling of trapped neutral atoms to Rydberg states. This approach allows for the tunability of all relevant terms in an Ising Hamiltonian with $1/r^6$ interactions in a transverse and longitudinal field. This review summarizes the recent progress of these implementations in Rydberg lattices with site-resolved detection. The strong correlations in this quantum Ising model have been observed in several experiments up to the point of crystallization. In systems with a diameter small compared to the Rydberg blockade radius, the number of excitations is maximally one in the so-called superatom regime.

Motivation & Objective

• To investigate finite-range interacting spin models beyond nearest-neighbor interactions using Rydberg atoms in optical lattices.
• To explore the transition from the superatom regime, where only one Rydberg excitation is allowed due to blockade, to many-body correlated phases.
• To observe and characterize quantum crystallization in finite-range interacting spin systems via site-resolved imaging.
• To enable tunable Ising Hamiltonians with controllable transverse and longitudinal fields using Rydberg state coupling.
• To extend quantum simulation to exotic phases such as supersolids and glassy states via Rydberg dressing techniques.

Proposed method

• Map the Rydberg Hamiltonian to an effective spin-1/2 Ising model using near-resonant laser coupling to Rydberg states.
• Implement tunable $1/r^6$ interactions via van der Waals dipole-dipole coupling between Rydberg-excited atoms.
• Use site-resolved imaging to detect individual spin configurations and measure spatial correlation functions with single-site resolution.
• Control the transverse field via Rabi frequency and longitudinal field via external magnetic fields to tune the Ising Hamiltonian parameters.
• Apply Rydberg dressing—off-resonant coupling to Rydberg states—to engineer long-lived effective interactions and enable atomic motion in the lattice.
• Utilize the frozen Rydberg gas approximation, neglecting atomic motion, to focus on internal spin dynamics in the strongly interacting regime.

Experimental results

Research questions

• RQ1 How do finite-range interactions in Ising models manifest in Rydberg-dressed atomic systems with tunable interaction ranges?
• RQ2 What are the signatures of quantum crystallization in finite Rydberg systems with long-range interactions?
• RQ3 How does the superatom regime emerge when the system size is smaller than the Rydberg blockade radius?
• RQ4 Can Rydberg dressing enable the realization of exotic quantum phases such as supersolids or cluster Luttinger liquids?
• RQ5 What are the experimental limits on coherence and control in long-range interacting spin systems using Rydberg atoms?

Key findings

• The superatom regime is achieved when the system diameter is smaller than the Rydberg blockade radius, restricting the number of excitations to one.
• In larger systems, strong correlations and spin crystallization were experimentally observed using site-resolved detection in Rydberg-dressed optical lattices.
• Finite-range Ising models with $1/r^6$ interactions were realized with full tunability of transverse and longitudinal fields via laser coupling.
• Site-resolved imaging enabled direct measurement of spatial spin correlation functions, confirming the emergence of ordered phases.
• Rydberg dressing was experimentally demonstrated in few-body and many-body systems, enabling longer effective lifetimes and access to new interaction regimes.
• Theoretical proposals for exotic phases—such as supersolid droplet crystals and glassy states—were supported by experimental progress toward their realization.