▁are ▁further ▁divided ▁into ▁quantum ▁simulation , ▁quantum ▁an ne aling , ▁and ▁ad i ab atic ▁quantum ▁computation . ▁Digital ▁quantum ▁computers ▁use ▁quantum ▁logic ▁gates ▁to ▁do ▁computation . ▁Both ▁approaches ▁use ▁quantum ▁bits ▁or ▁qu bits . ▁There ▁are ▁currently ▁a ▁number ▁of ▁significant ▁obst acles ▁in ▁the ▁way ▁of ▁construct ing ▁useful ▁quantum ▁computers . ▁In ▁particular , ▁it ▁is ▁difficult ▁to ▁maintain ▁the ▁quantum ▁states ▁of ▁qu bits ▁as ▁they ▁are ▁pr one ▁to ▁quantum ▁de co her ence , ▁and ▁quantum ▁computers ▁require ▁significant ▁error ▁correction ▁as ▁they ▁are ▁far ▁more ▁pr one ▁to ▁errors ▁than ▁classical ▁computers . ▁ ▁Any ▁computational ▁problem ▁that ▁can ▁be ▁solved ▁by ▁a ▁classical ▁computer ▁can ▁also , ▁in ▁principle , ▁be ▁solved ▁by ▁a ▁quantum ▁computer . ▁Con vers ely , ▁quantum ▁computers ▁obey ▁the ▁Church – T uring ▁th esis ; ▁that ▁is , ▁any ▁computational ▁problem ▁that ▁can ▁be ▁solved ▁by ▁a ▁quantum ▁computer ▁can ▁also ▁be ▁solved ▁by ▁a ▁classical ▁computer . ▁While ▁this ▁means ▁that ▁quantum ▁computers ▁provide ▁no ▁additional ▁power ▁over ▁classical ▁computers ▁in ▁terms ▁of ▁comput ability , ▁they ▁do ▁in ▁theory ▁provide ▁additional ▁power ▁when ▁it ▁comes ▁to ▁the ▁time ▁complexity ▁of ▁solving ▁certain ▁problems . ▁Not ably , ▁quantum ▁computers ▁are ▁believed ▁to ▁be ▁able ▁to ▁quickly ▁solve ▁certain ▁problems ▁that ▁no ▁classical ▁computer ▁could ▁solve ▁in ▁any ▁feas ible ▁amount ▁of ▁time — a ▁fe at ▁known ▁as ▁" quant um ▁supre m acy ". ▁The ▁study ▁of ▁the ▁computational ▁complexity