Dark Matter Detection through Rydberg Atom Transducer

Abstract

Ultralight bosonic dark matter with masses in the meV range, corresponding to terahertz (THz) Compton frequencies, remains largely unexplored due to the difficulty of achieving both efficient signal conversion and single-photon-sensitive detection at THz frequencies. We propose a hybrid detection architecture that integrates a dielectric haloscope, Rydberg-atom transducer, and superconducting nanowire single-photon detection within a unified cryogenic platform operating at $\lesssim 1\,\text{K}$. The dielectric haloscope converts dark matter into THz photons via phase-matched resonant enhancement, achieving form factors $C \sim 0.4$ and loaded quality factors $Q_L \sim 10^4$. A cold $^{87}$Rb ensemble then coherently up-converts the THz signal to the optical domain through six-wave mixing among Rydberg states. The intrinsic directionality and narrow bandwidth ($Δν_{\mathrm{atomic}} \sim 1\,\text{MHz}$) of this process provide extra suppression of isotropic thermal backgrounds. With 10 days of integration at $0.3\,\text{K}$, we project sensitivity to the axion-photon coupling $g_{aγγ} \sim 10^{-13}\,\mathrm{GeV}^{-1}$ at $m_a \sim 0.4\,\text{meV}$, reaching the QCD axion band and opening the THz window for searches of both axion and dark photon dark matter.

Figures (7)

• Figure 1: Projected sensitivities of our detection setup via DM-THz-Optical conversion for axion DM, $a$, (left) and dark photon DM, $A'$(right), assuming $C=0.4$ and five layers for the dielectric haloscope. For the axion DM search, we further assume that $B_0=10$ T, an integration time of $t=10$ days per experiment, and $T = 0.3\,\text{K}$ with $Q=10^4$ (solid) or $Q=5\times 10^4$ (dash-dotted). For the dark photon DM search, we assume $t=1$ day per experiment, and $Q=10^4$ at $T = 1.6$ K (dashed) or $T=0.3$ K (solid). Gray shading shows existing constraints from AxionLimits. The green band and yellow solid lines in the left panel show the predictions of QCD axion models DiLuzio:2016sbl and the projected sensitivity of IAXO IAXO:2019mpb, respectively. The purple shading in the right panel shows constraints from GigaBREAD BREAD:2023xhc. The purple lines in both panels show the projected sensitivities of BREAD with KIDS/TES (10 days, 0.3 K) BREAD:2021tpx.
• Figure 2: Schematic of the meV-DM cryogenic detection platform. Axion DM converts to THz photons in a dielectric haloscope, a stack of silicon (Si) disks and copper (Cu) mirrors in a magnetic field $\bm{B}_0$. The THz signal exits through a sub-wavelength $3\times3$ hole array in the end mirror and is focused by a cryogenic lens into a magnetically shielded Rydberg-atom ensemble, where six-wave mixing up-converts it to the optical domain. Spectral filtering and SNSPD readout complete the detection chain. The setup for detecting dark photon DM is similar but no magnetic field is needed for the haloscope.
• Figure 3: Simulated $E_x$ distribution at $0.1~\mathrm{THz}$, normalized to $|\bm E|_{\max}$. (a) $y$--$z$ cross section at $x=0$. (b) $x$--$z$ cross section at $y=0$. The $E_x$ component, parallel to the applied $\bm{B}_0$, is concentrated in the dielectric layers, yielding $C = 0.37$.
• Figure 4: (a) Six-wave-mixing energy-level scheme in $^{87}$Rb, converting THz photons ($\omega_T=m_{\rm DM}$) to optical photons ($\omega_L$). (b) Transition frequencies for various Rydberg state combinations. (c) Number of available transitions per frequency bin; 798 transitions span 0.1--1.5 THz. All 798 identified transitions are of the $|nS\rangle \to |n'P\rangle$ type.
• Figure A1: $F$ (Eq. \ref{['eq:F']}) as a function of THz frequency.