X0508 4 2024-09-23 0001816431 Quantum-Si Inc QSI 0002032947 Vieceli John S. C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true Chief Product Officer false Class A Common Stock 2024-09-23 4 S 0 2192 0.9459 D 166916 D Class A Common Stock 2024-09-24 4 S 0 2117 0.9307 D 164799 D The sales reported in this Form 4 were effected to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs") that were granted on March 15, 2024. The sale is mandated by the Issuer's election to require the satisfaction of tax withholding obligations through a "sell to cover" transaction and does not represent a discretionary trade by the reporting person. Represents the weighted average sales price per share. The shares sold at prices ranging from $0.9111 to $0.964 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $0.89 to $0.965 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. /s/ Christian LaPointe, Ph.D., Attorney-in-Fact 2024-09-25