Short answer: Rydberg dressing mixes a small amount of a highly excited Rydberg state into ground-state atoms, which gives them tunable long-range interactions. A 2016 Nature Physics paper reported a two-dimensional synthetic spin lattice, a 2022 Physical Review Letters paper reported distance-selective dressed interactions, and a 2023 Physical Review Letters paper reported spin-squeezed ensembles of 200 cesium atoms. These are laboratory experiments on atom arrays.
2016: a synthetic spin lattice
The Nature Physics abstract says ultracold atoms in optical lattices are ideal for studying frustrated or topological magnetic phases and supersolids, but control of strong long-range interactions between distant ground-state atoms had remained a long-standing goal. Optical dressing, through off-resonant laser coupling to Rydberg states, is one way to tailor such interactions. The authors report coherent Rydberg dressing used to implement a two-dimensional synthetic spin lattice. Single-atom-resolved interferometric measurements of the many-body dynamics probe the interactions and reveal their tunable range and anisotropy. They call this the first step toward studying exotic quantum magnets with laser-controlled Rydberg interactions in optical lattices.
2022: interactions that peak at one distance
The Physical Review Letters abstract says measurement-based quantum computing relies on rapid creation of large-scale entanglement in a register of stable qubits. Atomic arrays store information well and entanglement can be made with Rydberg states, but isolating pairs during a gate is difficult because Rydberg interactions have long tails at large distances.
The authors engineer distance-selective interactions, strongly peaked in distance, through off-resonant laser coupling of molecular potentials between Rydberg atom pairs. Using quantum gas microscopy, they verify the dressed interactions by observing correlated phase evolution with many-body Ramsey interferometry. They identify atom loss and coupling to continuum modes as limitations of the present scheme and outline ways to mitigate them. These ideas are plans.
2023: spin squeezing with dressing
The second Letter reports an array of spin-squeezed ensembles of cesium atoms created by Rydberg dressing. The authors optimize interaction coherence with a stroboscopic dressing sequence that suppresses super-Poissonian loss. They prepare squeezed states of 200 atoms with a metrological squeezing parameter of 0.77 (uncertainty 0.09), quantifying the reduction in phase variance below the standard quantum limit. They realize metrological gain across three spatially separated ensembles in parallel, with squeezing strength controlled by the local intensity of the dressing light. They say the method could enhance tests of fundamental physics with arrays of atomic clocks and enable quantum-enhanced imaging of electromagnetic fields, which are expectations.
How the three connect
The papers move from many-body physics to engineering. The 2016 work shows that dressed interactions can be probed and tuned, the 2022 work shapes them so they act over a chosen distance, and the 2023 work applies them to produce a metrological resource. The sequence is a reading of the three abstracts, and the authors do not present it as one program.
Limits
A squeezing parameter of 0.77 is a modest gain, and the 2022 abstract names atom loss as a present limitation. None of the three reports a gate between individual qubits or a computation.
FAQ
What is Rydberg dressing?
Off-resonant laser coupling of ground-state atoms to Rydberg states, to engineer interactions.
What did the 2016 paper build?
A two-dimensional synthetic spin lattice with tunable interaction range and anisotropy.
What limits the 2022 scheme?
Atom loss and coupling to continuum modes, per the authors.
How much squeezing was seen?
A parameter of 0.77 for 200 cesium atoms in 2023.
Is it a quantum computer?
No. These are many-body and metrology experiments.
All field notes