Why Is Quantum-Si ($QSI) Stock Up +27% Today? (Find out why any stock moved today on Tickeron.) QSI shares surged roughly 27%, climbing from a prior close of $1.22 to about $1.55 in midday trading. The primary catalyst was a development milestone: the company demonstrated detection of 19 amino acids on its next-generation Proteus platform. H.C. Wainwright reaffirmed a Buy rating and a $4.00 price target following the announcement. The rally reflects renewed optimism around the Proteus commercial launch, targeted for the second quarter of 2027. $PACB $AXON $VCYT