{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f7172303d670dc40e512de58bda406bf8498666132daf42b5be4bbd3f1b07838","created":"2026-10-03T07:18:01Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"334d823d16d98ffea01e1c7da5bbda55a7468fffa7ed5c83134ffec6a4d8207e","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.qubit-decoherence-defects.dominant-loss-interface","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Energy leaks from qubits into defects at several places: metal-air, metal-substrate and substrate-air surfaces, the substrate interior and the junction itself. Which of these limits the best current qubits is not settled.","posed_since":"","precise":"For Ta- or Nb-based transmons with $T_{1}$ from $\\sim 0.3\\,\\mathrm{ms}$ to above $1\\,\\mathrm{ms}$ at $\\sim 4-5\\,\\mathrm{GHz}$ on sapphire or high-resistivity Si, determine the loss tangents $\\tan \\delta_{i}$ and participation ratios $p_{i}$ of the metal-air, metal-substrate, substrate-air, substrate bulk and junction regions, and identify which term dominates $1/Q = \\sum_{i} p_{i}\\tan \\delta_{i}$ plus non-dielectric channels.","problem_ref":null,"references":"","settled_by":"Participation-resolved loss measurements on resonators and qubits of varied geometry from one fabrication process, with surface chemistry characterized by x-ray photoelectron spectroscopy and bulk substrate loss measured separately.","status_note":"","title":"Which interface dominates dielectric loss in millisecond transmons?","topic_ref":"228b58abc42aea116ba49a5712e2571d336009d0276f52a950ef3939fbb3059f"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d861da47304e085ce6745af9b19b6e6c4b027d039d0bc52532fdcecf12c1bd79","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6822adf531a78ffa8deae7cc5ece9409613c48273c4224662443d9505448bf77","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"y0fGU2fIcJalyczHkWjNm5MVNELsw3izP2ZCjvpFSpqc4F1g5fetEfY_aFvF9x-YWzeTyKT02HA5aDIy3gr-Aw"},"schema":"pubphys.envelope/1"},"record_hash":"d861da47304e085ce6745af9b19b6e6c4b027d039d0bc52532fdcecf12c1bd79","leaf_index":1137}