XML 13 R1.htm IDEA: XBRL DOCUMENT v3.21.2
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2021
Nov. 09, 2021
Entity Listings [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2021  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q3  
Document Transition Report false  
Entity File Number 001-39486  
Entity Registrant Name QUANTUM-SI INCORPORATED  
Entity Central Index Key 0001816431  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 85-1388175  
Entity Address, Address Line One 530 Old Whitfield Street  
Entity Address, City or Town Guilford  
Entity Address, State or Province CT  
Entity Address, Postal Zip Code 06437  
City Area Code 203  
Local Phone Number 458-7100  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Class A Common Stock [Member]    
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   117,478,783
Class B Common Stock [Member]    
Entity Listings [Line Items]    
Entity Common Stock, Shares Outstanding   19,937,500
Redeemable Warrants [Member]    
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