Scientists are now convinced of the existence of dark matter, without which the galaxies of our universe could not exist. But unlike ordinary matter, dark matter is not sensitive to electromagnetic force. It cannot absorb, reflect or emit light, which makes it very difficult to detect. Only the effect of gravity on visible matter makes it possible to infer its presence.
Detection of the presence of axions by spinning ions
Several experiments have been conducted, notably at CERN’s Large Hadron Collider, in an attempt to discover the virtual particles that make up this form of matter. Among them is the axon, a supposedly stable particle, electrically neutral and of very low mass, which, according to theoretical models, would have negligible effects on electromagnetism.
Thus a team from the National Institute of Standards and Technology (NIST) developed a new device capable of detecting these axes. ” We have found a protocol that exploits our ability to produce quantum entanglement states that is very sensitive to the small displacements of ions driven by weak electric fields. ‘, explains Kevin Gilmore, lead author of The article describing this research.
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This new quantum sensor consists of 150 beryllium ions. These are confined to the so-called Penning trap, a device that allows charged particles to be stored through a combination of a regular magnetic field and a constant quadrupole electric field. In this way, the ions organize themselves into a two-dimensional crystal only 200 μm thick.
When exposed to an electric field, all the ions in the crystal move in a collective motion, up and down—just like the skin of a vibrating cylinder. Therefore, if it is isolated from any external electric field and still begins to vibrate, this could indicate that the axis – or any particle of dark matter – has passed through it.
in a The device designed by NIST researchers, this collective motion is entangled (or entangled) with the electronic spin of the ions before the start of the experiment, using a specific type of laser light. All ions have been brought to the state above from their spindle. Thus any change in the direction of the spin necessarily translates into a displacement, due to an electric field generated by the axion.
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In other words, the behavior of the ionic crystal – in terms of motion – can be inferred directly from the spin measurements. However, it is relatively easy to achieve: if the ions are in a spin state above, they scatter light, but if they are in a state of rotation UnderThey remain dark. ” The vibrational mode of the crystal center of mass acts as a high-quality mechanical oscillator, and the collective electronic rotation acts as a measuring device » Summarize the researchers in their article.
An electric field sensor with unprecedented sensitivity
Quantum sensors can detect and measure signals that are undetectable with their classical counterparts. It is thus a promising tool in many areas of basic science. Among the many systems that are conceptualized as quantum sensors, those based on ion trapping are particularly interesting because of the precise control of experimenters over their parameters and the possibility of introducing entanglement into the system.
This ultra-precise sensor displays unprecedented power: it can measure external electric fields of the same frequency of vibration as a crystal, with a sensitivity over 10 times that of all atomic devices developed to date! The researchers report an electric field measurement sensitivity of 240 ± 10 nanovolts per meter in one second. ” This means that we demonstrated the advantage of detection using quantum effects (entanglement), which is not significant. “,” Gilmore says to Physicist. The device is so precise that it may be sensitive enough to detect dark matter axes, which are thought to generate tiny oscillating electric fields.
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After demonstrating this principle, the team now plans to create much larger ion crystals: Ultimately, they want to develop a 3D crystal made up of about 100,000 ions. Increasing the number of ions will not only significantly increase the detection power, by 30 times according to the researchers, but also reduce the frequency fluctuations of the crystal’s vibrations. ” If we can improve on this aspect, this experiment could become an essential resource for discovering dark matter. Anna Maria Ray, co-author of the study.
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