United States securities and exchange commission logo

                          August 18, 2023

       Jeffrey Hawkins
       Chief Executive Officer
       Quantum-Si Incorporated
       29 Business Park Drive
       Branford, Connecticut 06405

                                                        Re: Quantum-Si
Statement on Form S-3
                                                            Filed August 11,
                                                            File No. 333-273934

       Dear Jeffrey Hawkins:

              This is to advise you that we have not reviewed and will not
review your registration

               Please refer to Rules 460 and 461 regarding requests for
acceleration. We remind you
       that the company and its management are responsible for the accuracy and
adequacy of their
       disclosures, notwithstanding any review, comments, action or absence of
action by the staff.

                                                        Please contact Benjamin
Richie at 202-551-7857 with any questions.


                          Division of Corporation Finance

                          Office of Industrial Applications and

       cc:                                              Samantha Silver