X0508 4 2026-03-05 0001816431 Quantum-Si Inc QSI 0001534980 Kummeth Charles R. C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true false Class A Common Stock 2026-03-05 4 P 0 500000 0.9196 A 855000 D Represents the weighted average purchase price per share. The shares were purchased at prices ranging from $0.8906 to $0.9735 per share. Full information regarding the number of shares purchased 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. 2026-03-09