Long-baseline Quantum Sensor Network as a Dark Matter Haloscope

Academic Background

Ultralight dark photons, as one of the significant candidates for dark matter, have attracted extensive theoretical and experimental attention. According to the kinetic mixing mechanism, when dark photons couple with standard model photons, coherent electromagnetic waves are produced, and these waves should have spatial correlations within the de Broglie wavelength range of the dark photons. However, despite abundant evidence from astrophysics over the past eighty years supporting the existence of dark matter, direct detection of its non-gravitational interactions with standard model particles and fields has not yet achieved a breakthrough. To address this challenge, many theories have been proposed, some of which predict the existence of new fundamental particles, such as axions and dark photons.

Source

This paper, titled “Long-baseline quantum sensor network as dark matter haloscope,” was completed by several researchers from the University of Science and Technology of China and related research institutions, including Min Jiang, Taizhou Hong, Dongdong Hu, Yifan Chen, Fengwei Yang, Tao Hu, Xiaodong Yang, Jing Shu, Yue Zhao, Xinhua Peng, and Jiangfeng Du. The paper was published in Nature Communications, accepted on April 4, 2024, and published in 2024.

Research Workflow

The research work consists of several main steps: 1. The study configures 15 atomic magnetometers distributed in two electromagnetic shielding rooms in Harbin and Suzhou, China, with a distance of 1700 km between the two experimental locations. 2. All magnetometers are synchronized to the Global Positioning System (GPS) to ensure real-time data comparison between the two locations. 3. The atomic magnetometers have extremely high sensitivity, reaching the femtoTesla (fT) level, and can detect radio signals of electromagnetic fields near the shielding walls. 4. By synchronizing data and conducting long-baseline measurements, many local noise sources are significantly reduced, enhancing the credibility of dark photon signal detection. 5. The kinetic mixing parameter ε is used as a constraint to evaluate the influence of dark photon dark matter within the mass range of 4.1feV to 2.1PeV.

Experimental Methods and Data Analysis

• Experimental Equipment: An electromagnetic shielding room with five layers of shielding, with an internal dimension of 2×2×2m³ per room.
• Data Capture and Processing: All data recorded by the atomic magnetometer network are collected through a custom data acquisition system and synchronized with GPS time, calculating the cross-correlation spectrum for each pair of magnetometers.
• Noise Handling: Using a long-baseline array to distinguish between technical noise and potential dark photon signals, comparing noise levels and the correlation of signals to eliminate noise interference.

Main Results

1. Experimental data show that within the mass range of 4.1feV to 2.1PeV for dark photons, the kinetic mixing parameter ε can be significantly constrained. The measured sensitivity is three orders of magnitude higher than that of ground-based experiments, about 5×10^-6.
2. By cross-correlating data from all magnetometers, the experiment demonstrated the first experimental detection of correlated signals of dark photons over a distance exceeding 1000 km.
3. During the experiment, the validity and reliability of dark photon signal detection were ensured by eliminating technical noise and local background signals.

Conclusion and Significance

1. The research results provide the most stringent constraints on the kinetic mixing parameter of dark photons within the mass range of 4.1feV to 2.1PeV, far exceeding previous ground-based experiments.
2. Through the long-baseline quantum sensor network, large-scale noise from geographic and astronomical factors was significantly reduced, achieving high-sensitivity detection of dark photon signals.
3. This quantum sensor network technology offers new ideas and directions for future dark matter detection. Particularly with further optimization of experimental setups and an increase in the number of detection points, sensitivity an order of magnitude higher than the current level can be achieved.

Research Highlights

1. Using 15 synchronized atomic magnetometers, the experiment detected correlated signals of dark photons over a baseline of up to 1700 km for the first time.
2. The experiment provided the most stringent constraints on the kinetic mixing parameter within the mass range of 4.1feV to 2.1PeV, significantly enhancing the sensitivity of dark photon signal detection.
3. The use of a five-layer magnetic shielding electromagnetic room greatly improved the detection efficiency for dpdm signals, showcasing the potential of large shielding rooms for the collection of weak radio signals.

In the future, the detection capability of dark photon dark matter can be further enhanced by increasing the number of magnetometers, expanding the size of the shielding rooms, and optimizing the sensitivity of the magnetometers, potentially exploring new parameter spaces beyond existing astronomical and cosmological constraints.