 
 <prompt> Wetin be di type of particle wey no dey made of matter? Based on di question wey dey above, write one context wey get di answer. E fit be 1 - 20 sentences. Context: <response>: In quantum mechanics and quantum field theory, dem talk say vacuum na di state wey get di lowest energy (ground state of di Hilbert space). For quantum electrodynamics, dis vacuum dey call 'QED vacuum' to show say e different from di vacuum of quantum chromodynamics wey dem dey call QCD vacuum. QED vacuum na state wey no get any matter particles (wey be why dem call am vacuum), and no photons too. As dem talk before, e no dey possible to achieve dis state for experiment. (Even if all di matter particles somehow disappear from one place, e no go fit eliminate all di blackbody photons.) But e still dey give us good model for realizable vacuum, and e dey agree with plenty experimental observations as dem go talk next. 