<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2025"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:qsi="http://quantum-si.com/20250926"
  xmlns:us-gaap="http://fasb.org/us-gaap/2025"
  xmlns:xbrldi="http://xbrl.org/2006/xbrldi"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="qsi-20250926.xsd" xlink:type="simple"/>
    <context id="c20250926to20250926">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001816431</identifier>
        </entity>
        <period>
            <startDate>2025-09-26</startDate>
            <endDate>2025-09-26</endDate>
        </period>
    </context>
    <context id="c20250926to20250926_StatementClassOfStockAxis_CommonClassAMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001816431</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">us-gaap:CommonClassAMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2025-09-26</startDate>
            <endDate>2025-09-26</endDate>
        </period>
    </context>
    <context id="c20250926to20250926_StatementClassOfStockAxis_RedeemableWarrantsEachWholeWarrantExercisableForOneShareOfClassACommonStockEachAtAnExercisePriceOf1150PerShareMember">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001816431</identifier>
            <segment>
                <xbrldi:explicitMember dimension="us-gaap:StatementClassOfStockAxis">qsi:RedeemableWarrantsEachWholeWarrantExercisableForOneShareOfClassACommonStockEachAtAnExercisePriceOf1150PerShareMember</xbrldi:explicitMember>
            </segment>
        </entity>
        <period>
            <startDate>2025-09-26</startDate>
            <endDate>2025-09-26</endDate>
        </period>
    </context>
    <dei:AmendmentFlag
      contextRef="c20250926to20250926"
      id="Fact_110c27a812a44a22a539cd50a531f850">false</dei:AmendmentFlag>
    <dei:EntityCentralIndexKey
      contextRef="c20250926to20250926"
      id="Fact_324ac28523df44de85ba526770a82883">0001816431</dei:EntityCentralIndexKey>
    <dei:DocumentType
      contextRef="c20250926to20250926"
      id="Fact_1a5f9a291f954c95bd24028295b47b6d">8-K</dei:DocumentType>
    <dei:DocumentPeriodEndDate
      contextRef="c20250926to20250926"
      id="Fact_ec6595465f6445c28ca676a5d6fdc6cb">2025-09-26</dei:DocumentPeriodEndDate>
    <dei:EntityRegistrantName
      contextRef="c20250926to20250926"
      id="Fact_8902d9f3bcf44f0db5e001218706c755">QUANTUM-SI INCORPORATED</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="c20250926to20250926"
      id="Fact_ba179cb5779a4b43a0eadccadceeedde">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityFileNumber
      contextRef="c20250926to20250926"
      id="Fact_092d9a341cf749059ec73a66033882d9">001-39486</dei:EntityFileNumber>
    <dei:EntityTaxIdentificationNumber
      contextRef="c20250926to20250926"
      id="Fact_028019bee8f34f3e9172feaaba99a9b4">85-1388175</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="c20250926to20250926"
      id="Fact_f88471a82d684c9589c8587dbccb46c1">29 Business Park Drive</dei:EntityAddressAddressLine1>
    <dei:EntityAddressCityOrTown
      contextRef="c20250926to20250926"
      id="Fact_284699d80db64fe39dbfc53cfc64415f">Branford</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="c20250926to20250926"
      id="Fact_cee0802fa73e440cbfe0c3a4c5580e25">CT</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="c20250926to20250926"
      id="Fact_8a71864a355f44b19ae3f8a3c13fb193">06405</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="c20250926to20250926"
      id="Fact_4992bfcfd1054aa7a075d796b2dc96d3">866</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="c20250926to20250926"
      id="Fact_ca2e8a5a0b7240598abe3b31e458a003">688-7374</dei:LocalPhoneNumber>
    <dei:WrittenCommunications
      contextRef="c20250926to20250926"
      id="Fact_94c1f9fe5a644b9892cb17ef77992512">false</dei:WrittenCommunications>
    <dei:SolicitingMaterial
      contextRef="c20250926to20250926"
      id="Fact_2b43b6507722451cb0f4c91bf5ae8850">false</dei:SolicitingMaterial>
    <dei:PreCommencementTenderOffer
      contextRef="c20250926to20250926"
      id="Fact_7dc65315bac74a8c85edc18b483206a6">false</dei:PreCommencementTenderOffer>
    <dei:PreCommencementIssuerTenderOffer
      contextRef="c20250926to20250926"
      id="Fact_20d315bb40044b649b388baecfa0442d">false</dei:PreCommencementIssuerTenderOffer>
    <dei:Security12bTitle
      contextRef="c20250926to20250926_StatementClassOfStockAxis_CommonClassAMember"
      id="Fact_05c49ee7819b426ca4eff1c3434c9089">Class A common stock, par value $0.0001 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="c20250926to20250926_StatementClassOfStockAxis_CommonClassAMember"
      id="Fact_4c65814d32d9423c8409f12171010d50">QSI</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="c20250926to20250926_StatementClassOfStockAxis_CommonClassAMember"
      id="Fact_3ffae4e4f91d48828deb05b09ab52b75">NASDAQ</dei:SecurityExchangeName>
    <dei:Security12bTitle
      contextRef="c20250926to20250926_StatementClassOfStockAxis_RedeemableWarrantsEachWholeWarrantExercisableForOneShareOfClassACommonStockEachAtAnExercisePriceOf1150PerShareMember"
      id="Fact_b1a229f5c271487ba2c023d9722da012">Redeemable warrants, each whole warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="c20250926to20250926_StatementClassOfStockAxis_RedeemableWarrantsEachWholeWarrantExercisableForOneShareOfClassACommonStockEachAtAnExercisePriceOf1150PerShareMember"
      id="Fact_1027ab9440864501bb4e644efcf525eb">QSIAW</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="c20250926to20250926_StatementClassOfStockAxis_RedeemableWarrantsEachWholeWarrantExercisableForOneShareOfClassACommonStockEachAtAnExercisePriceOf1150PerShareMember"
      id="Fact_2d577f64b580438ba8033924c24e5103">NASDAQ</dei:SecurityExchangeName>
    <dei:EntityEmergingGrowthCompany
      contextRef="c20250926to20250926"
      id="Fact_03d6ed07151741bea29cf574e6711acd">false</dei:EntityEmergingGrowthCompany>
</xbrl>
