ized ▁energy ▁levels ▁for ▁tra pped ▁charged ▁particles ▁like ▁electrons ▁and ▁pro tons . ▁The ▁earth ' s ▁magnetic ▁field ▁in ▁effect ▁places ▁the ▁earth ▁in ▁an ▁elect romagnet ic ▁cav ity . ▁ ▁Phys ical ▁description ▁of ▁elect romagnet ic ▁cav ities ▁▁ ▁Elect romagnet ic ▁cav ities ▁are ▁represented ▁by ▁potential ▁well s , ▁also ▁called ▁boxes , ▁which ▁can ▁be ▁of ▁limited ▁or ▁un limited ▁depth ▁V 0 . ▁ ▁Quant um - me chan ic ▁boxes ▁are ▁described ▁by ▁the ▁time - in dependent ▁Sch r öd inger ▁equation : ▁ ▁with ▁the ▁additional ▁boundary ▁conditions ▁▁ ▁the ▁wave ▁function ▁is ▁conf ined ▁to ▁the ▁box ▁( in finite ▁deep ▁potential ▁well ) ▁or ▁approaches ▁zero ▁as ▁the ▁distance ▁from ▁the ▁wall ▁increases ▁to ▁infinity , ▁thus ▁normal is able ▁ ▁the ▁wave ▁function ▁must ▁be ▁continuous ▁ ▁the ▁derivative ▁of ▁the ▁wave ▁function ▁must ▁be ▁continuous ▁which ▁leads ▁to ▁real ▁solutions ▁for ▁the ▁wave ▁functions ▁if ▁the ▁net ▁energy ▁of ▁the ▁particle ▁is ▁negative ., ▁i . e . ▁if ▁the ▁particle ▁is ▁in ▁a ▁bound ▁state . ▁ ▁App lications ▁of ▁elect romagnet ic ▁cav ities ▁▁ ▁Elect rons ▁which ▁are ▁tra pped ▁in ▁an ▁elect romagnet ic ▁cav ity ▁are ▁in ▁a ▁bound ▁state ▁and ▁thus ▁organ ise ▁themselves ▁as ▁they ▁do ▁in ▁a ▁regular ▁atom , ▁thus ▁express ing ▁chemical - like ▁behaviour . ▁Several ▁research ers ▁have ▁proposed ▁to ▁develop ▁program m able ▁matter ▁by ▁varying ▁the ▁number ▁of ▁tra pped ▁electrons ▁in ▁those