X0508 4 2024-03-15 0001816431 Quantum-Si Inc QSI 0001557736 Keyes Jeffry R. C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true Chief Financial Officer false Class A Common Stock 2024-03-15 4 A 0 346820 0 A 396820 D Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in equal quarterly installments over four years beginning on June 20, 2024, subject to Mr. Keyes' continued service through the applicable vesting date. /s/ Christian LaPointe, Ph.D., Attorney-in-Fact 2024-03-18