Manybody Interferometry of Quantum Fluids

Characterizing strongly correlated matter is an increasingly central challenge in quantum science, where structure is often obscured by massive entanglement. From semiconductor heterostructures and 2D materials to synthetic atomic, photonic and ionic quantum matter, progress in preparation of manybody quantum states is accelerating, opening the door to new approaches to state characterization. It is becoming increasingly clear that in the quantum regime, state preparation and characterization should not be treated separately – entangling the two processes provides a quantum advantage in information extraction. From Loschmidt echo to measure the effect of a perturbation, to out-of-time-order-correlators (OTOCs) to characterize scrambling and manybody localization, to impurity interferometry to measure topological invariants, and even quantum Fourier transform-enhanced sensing, protocols that blur the distinction between state preparation and characterization are becoming prevalent. Here we present a new approach which we term ‚manybody Ramsey interferometry‘ that combines adiabatic state preparation and Ramsey spectroscopy: leveraging our recently-developed one-to-one mapping between computational-basis states and manybody eigenstates, we prepare a superposition of manybody eigenstates controlled by the state of an ancilla qubit, allow the superposition to evolve relative phase, and then reverse the preparation protocol to disentangle the ancilla while localizing phase information back into it. Ancilla tomography then extracts information about the manybody eigenstates, the associated excitation spectrum, and thermodynamic observables. This work opens new avenues for characterizing manybody states, paving the way for quantum computers to efficiently probe quantum matter.