Scalable architecture for dark photon searches: Superconducting-qubit proof of principle

  1. Runqi Kang,
  2. Qingqin Hu,
  3. Xiao Cai,
  4. Wenlong Yu,
  5. Jingwei Zhou,
  6. Xing Rong,
  7. and Jiangfeng Du
The dark photon is a well-motivated candidate of dark matter due to its potential to open the window of new physics beyond the Standard Model. A fundamental mass-range-sensitivity dilemma
is always haunting the dark photon searching experiments: The resonant haloscopes have excellent sensitivity but are narrowband, and vice versa for the non-resonant ones. A scalable architecture integrating numerous resonant haloscopes will be a desirable solution to this dilemma. However, even the concept of scalable searching remains rarely explored, due to the size limitation of conventional haloscopes imposed by the dark photon wavelength. Here we propose and demonstrate a novel architecture using superconducting qubits as sub-wavelength haloscope units. By virtue of the scalability of superconducting qubits, it is possible to integrate multiple qubits with different frequencies on a chip-scale device. Furthermore, the frequencies of the qubits can be tuned to extend the searching mass range. Thus, our architectures allow for searching for dark photons in a broad mass range with high sensitivity. As a proof-of-principle experiment, we designed and fabricated a three-qubit chip and successfully demonstrated a scalable dark-photon searching. Our work established constraints on dark photons in the mass range of 15.632 μeV∼15.638 μeV, 15.838 μeV∼15.845 μeV, and 16.463 μeV∼16.468 μeV, simultaneously, and the constraints are much more stringent than the cosmology constraints. Our work can be scaled up in the future to boost the scrutiny of new physics and extended to search for more dark matter candidates, including dark photons, axions and axion-like particles.

Analogue Hawking Radiation and Sine-Gordon Soliton in a Superconducting Circuit

  1. Zehua Tian,
  2. and Jiangfeng Du
We propose the use of a waveguide-like transmission line based on direct-current superconducting quantum interference devices (dc-SQUID) and study the sine-Gordon (SG) equation which
characterises the dynamical behavior of the superconducting phase in this transmission line. Guided by the duality between black holes in Jackiw-Teitelboim (JT) dilaton gravity and solitons in sine-Gordon field theory, we show how to, in our setup, realize 1 + 1 dimensional black holes as solitons of the sine-Gordon equation. We also study the analogue Hawking radiation in terms of the quantum soliton evaporation, and analyze its feasibility within current circuit quantum electrodynamics (cQED) technology. Our results may not only facilitate experimentally understanding the relation between Jackiw-Teitelboim dilaton gravity and sine-Gordon field theory, but also pave a new way, in principle, for the exploration of analogue quantum gravitational effects.