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                          July 8, 2021

       John Stark
       Chief Executive Officer
       Quantum-Si Incorporated
       530 Old Whitfield Street
       Guilford, Connecticut 06437

                                                        Re: Quantum-Si
Incorporated
                                                            Registration
Statement on Form S-1
                                                            Filed July 2, 2021
                                                            File No. 333-257676

       Dear Mr. Stark:

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

               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 Alan
Campbell at 202-551-4224 with any questions.




                          Sincerely,


                          Division of Corporation Finance

                          Office of Life Sciences