▁U . S . ▁National ▁Aer onaut ics ▁and ▁Space ▁Administration ▁( N AS A ), ▁published ▁a ▁paper ▁in ▁which ▁they ▁claimed ▁to ▁have ▁achieved ▁quantum ▁supre m acy . ▁While ▁some ▁have ▁disput ed ▁this ▁claim , ▁it ▁is ▁still ▁a ▁significant ▁mil estone ▁in ▁the ▁history ▁of ▁quantum ▁computing . ▁ ▁There ▁are ▁several ▁models ▁of ▁quantum ▁computing , ▁including ▁the ▁quantum ▁circuit ▁model , ▁quantum ▁T uring ▁machine , ▁ad i ab atic ▁quantum ▁computer , ▁one - way ▁quantum ▁computer , ▁and ▁various ▁quantum ▁cell ular ▁autom ata . ▁The ▁most ▁widely ▁used ▁model ▁is ▁the ▁quantum ▁circuit . ▁Quant um ▁circ uits ▁are ▁based ▁on ▁the ▁quantum ▁bit , ▁or ▁" qu bit ", ▁which ▁is ▁somewhat ▁analog ous ▁to ▁the ▁bit ▁in ▁classical ▁computation . ▁Q ub its ▁can ▁be ▁in ▁a ▁ 1 ▁or ▁ 0 ▁quantum ▁state , ▁or ▁they ▁can ▁be ▁in ▁a ▁super position ▁of ▁the ▁ 1 ▁and ▁ 0 ▁states . ▁However , ▁when ▁qu bits ▁are ▁measured ▁the ▁result ▁is ▁always ▁either ▁a ▁ 0 ▁or ▁a ▁ 1 ; ▁the ▁prob abilities ▁of ▁these ▁two ▁out comes ▁depend ▁on ▁the ▁quantum ▁state ▁that ▁they ▁were ▁in ▁immediately ▁prior ▁to ▁the ▁measurement . ▁Comput ation ▁is ▁performed ▁by ▁manip ulating ▁qu bits ▁with ▁quantum ▁logic ▁gates , ▁which ▁are ▁somewhat ▁analog ous ▁to ▁classical ▁logic ▁gates . ▁ ▁There ▁are ▁currently ▁two ▁main ▁approaches ▁to ▁phys ically ▁implementing ▁a ▁quantum ▁computer : ▁analog ▁and ▁digital . ▁Anal og ▁approaches