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SUMMARY:Superconducting Qubits as Single THz-Photon Detectors for Bosonic 
 Dark Matter Searches
DTSTART:20260629T080000Z
DTEND:20260629T100000Z
DTSTAMP:20260710T204300Z
UID:indico-event-18377@indico.global
DESCRIPTION:Speakers: Felix Wagner (ETH Zurich)\n\nThe detection of single
  photons at terahertz frequencies is notoriously difficult\, since wavelen
 gths are small\, making the application of haloscopes difficult\, while th
 e photon energy is also low\, making calorimetric detection impossible for
  current technologies. This combination defines the so-called THz gap\, wh
 ich extends through the laboratory search landscape for fundamental physic
 s. In the 0.1 THz to 1 THz band\, the strongest direct laboratory bound on
  a dark photon is χ ≲ 10^−8 over a narrow sub-band\, three to four or
 ders of magnitude weaker than the limits set by microwave haloscopes immed
 iately below 0.1 THz.\nNotably\, the superconducting gap of typical qubit-
 platform metals lies in this same energy range. Recent measurements identi
 fy thermal radiation in this band as the dominant source of Cooper-pair br
 eaking in state-of-the-art superconducting qubits\, a harmful source of er
 rors for superconducting quantum computers. Offset charge-sensitive superc
 onducting qubits are currently the only sensor technology that resolves th
 e tunneling of a single quasiparticle across a Josephson junction\, which 
 is the signal that follows the resonant absorption of a photon by the spur
 ious antenna mode of the qubit capacitor pad. We propose to exploit this c
 oupling — between the microwave-controllable electromagnetic qubit mode 
 and the THz-scale antenna mode of the capacitor island — to use the qubi
 t as a sensor of single photons sourced by fundamental physics in the THz 
 gap. The planned demonstrator instrument is a multiplexed qubit array with
  narrow-band\, frequency-tiled antenna modes\, coupled to a free-space opt
 ical collection chain and operated as a single-photon counter. For a per-c
 hannel dark count rate of 1 Hz and an effective collection area of order c
 entimeters squared\, a one-month exposure projects a reach on the dark-pho
 ton kinetic mixing parameter four to five orders of magnitude below the st
 rongest direct laboratory bound in this frequency range. \n\nhttps://indi
 co.global/event/18377/
LOCATION:Besprechungsraum 5 - 4. OG (PSK)
URL:https://indico.global/event/18377/
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