Shadow Tomography from Emergent State Designs in Analog Quantum Simulators.

We introduce a method that allows one to infer many properties of a quantum state-including nonlinear functions such as Rényi entropies-using only global control over the constituent degrees of freedom. In this protocol, the state of interest is first entangled with a set of ancillas under a fixed global unitary, before projective measurements are made. We show that when the unitary is sufficiently entangling, a universal relationship between the statistics of the measurement outcomes and properties of the state emerges, which can be connected to the recently discovered phenomeonon of emergent quantum state designs in chaotic systems. Thanks to this relationship, arbitrary observables can be reconstructed using the same number of experimental repetitions that would be required in classical shadow tomography [Huang et al., Nat. Phys. 16, 1050 (2020)NPAHAX1745-247310.1038/s41567-020-0932-7]. Unlike previous approaches to shadow tomography, our protocol can be implemented using only global Hamiltonian evolution, as opposed to qubit-selective logic gates, which makes it particularly well suited to analog quantum simulators, including ultracold atoms in optical lattices and arrays of Rydberg atoms.