Searching for Dark Matter with a Superconducting Qubit.

Area of Science:

• * Particle Physics
• * Astrophysics
• * Quantum Computing

Background:

• * Dark matter detection often relies on interactions with electromagnetic fields, converting dark matter particles into photons.
• * Current microwave frequency searches use resonant cavities and near-standard quantum limited (SQL) amplifiers.
• * Increased sensitivity requires moving beyond SQL detection limits to sub-SQL techniques.

Purpose of the Study:

• * To develop a novel microwave photon counting technique for enhanced dark matter detection.
• * To establish new exclusion limits for hidden photon dark matter.
• * To demonstrate a noise reduction method enabling faster future dark matter searches.

Main Methods:

• * Utilized a superconducting qubit for repeated quantum nondemolition measurements of cavity photons.
• * Applied a hidden Markov model analysis to significantly reduce noise below the quantum limit.
• * Operated a microwave cavity search for hidden photon dark matter.

Main Results:

• * Achieved noise reduction 15.7 dB below the quantum limit.
• * Established a new exclusion limit for hidden photon dark matter with kinetic mixing angle ε ≤ 1.68×10⁻¹⁵.
• * Demonstrated a technique that can speed up future dark matter searches by a factor of 1,300.

Conclusions:

• * The developed microwave photon counting technique offers a path to sub-SQL metrology.
• * This method significantly enhances sensitivity and speed for detecting low mass bosonic dark matter.
• * The technique has broader implications for quantum sensing and metrology beyond dark matter searches.