v3.25.4
Cover - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Feb. 25, 2026
Jun. 30, 2025
Entity Listings [Line Items]      
Document Type 10-K    
Document Annual Report true    
Current Fiscal Year End Date --12-31    
Document Period End Date Dec. 31, 2025    
Document Transition Report false    
Entity File Number 001-39486    
Entity Registrant Name QUANTUM-SI INCORPORATED    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 85-1388175    
Entity Address, Address Line One 29 Business Park Drive    
Entity Address, City or Town Branford    
Entity Address, State or Province CT    
Entity Address, Postal Zip Code 06405    
City Area Code 866    
Local Phone Number 688-7374    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 286.3
Documents Incorporated by Reference
The following documents (or parts thereof) are incorporated by reference into the following parts of this Form 10-K: Certain information required in Part III of this Annual Report on Form 10-K is incorporated by reference from the Registrant’s Proxy Statement for the 2026 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission.
    
Entity Central Index Key 0001816431    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Class A common stock      
Entity Listings [Line Items]      
Title of 12(b) Security Class A common stock, $0.0001 per share    
Trading Symbol QSI    
Security Exchange Name NASDAQ    
Entity Common Stock, Shares Outstanding   196,431,273  
Redeemable warrants      
Entity Listings [Line Items]      
Title of 12(b) Security Redeemable warrants, each whole warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share    
Trading Symbol QSIAW    
Security Exchange Name NASDAQ    
Class B common stock      
Entity Listings [Line Items]      
Entity Common Stock, Shares Outstanding   19,937,500