Abstract: Methods, systems, and apparatus for distributed ledger for physical material. In one aspect, a method includes obtaining a first set of information regarding a physical material to be verified, the first set of information including hundreds of values for channels of a spectrum of electromagnetic radiation emitted by the physical material in response to an irradiation of the physical material; obtaining a second set of information regarding the physical material to be verified; sending the first and second sets of information over the communication network to a verification computer system; receiving verification information; initiating addition of information usable to identify the first set of information and the digital signature to a distributed digital ledger; receiving confirmation of the addition of the information useable to identify the first set of information and the digital signature to the distributed digital ledger; and reporting that the physical material has been verified.

Abstract: The disclosure features methods for analyzing a sample, the methods including exposing the sample to plurality of pulses of electromagnetic radiation to convert a portion of the sample into a plasma, recording a spectrum of electromagnetic radiation emitted in response to each of the plurality of pulses to define a sequence of spectra for the sample, and using an electronic processor to determine information about the sample based on the spectra, where exposing the sample to the plurality of pulses of electromagnetic radiation includes directing the pulses to be incident on different spatial regions of the sample, and where a temporal delay between exposing the sample to each successive radiation pulse is constant.