Physicists have uncovered a unique aspect of the magnetic sense in animals.

Physicists have discovered two types of sensors in animals that can detect magnetic fields close to the quantum limit. This information could enhance our own designs of magnetometric devices. The study was published in the journal PRX Life 3, as reported by ScienceAlert.

Magnetoreception, the sense that allows living organisms to perceive magnetic fields to determine their location and direction of movement, evolved over a long period of time.

Physicists aimed to understand how biological solutions relate to advancements in magnetometer technology, assessing the energy resolution limits of three magnetoreception mechanisms, and found that at least two of them are in close proximity to the quantum detection limits of magnetic fields.

Today, accurately measuring the strength of a magnetic field requires a detailed and comprehensive understanding of the quantum nature of electromagnetism, which not only enhances sensitivity but also enables predictions of the physical limits of any measurement.

The basis for calculating the force of attraction and repulsion of a magnetic field is the ability to measure the energy contained within it. As our capacity to measure magnetism becomes increasingly precise, quantum uncertainty increasingly prevails. This issue is exacerbated by the tendency of quantum-level systems to entangle with their environment, further blurring the boundaries of energy softened by the magnetic field.

The energy resolution limit is a mixture of parameters representing the properties of a quantum system within the sensor's range, which includes estimating its uncertainty, the size of the perceived area, and the time of transmission during which the measurement is made. The end result is an energy unit over time, equivalent to a quantum unit known as Planck's constant, which allows engineers to compare existing technologies based on their accuracy level as well as assess the ability of any potential system to reach or even exceed what is considered the limit.

Currently, scientists believe that some living organisms detect the Earth's magnetic field through inductive, radical-pair, and magnetite mechanisms.

• Inductive mechanisms convert the energy of the magnetic field into electrical energy within a biological system, ultimately affecting its behavior.
• Radical-pair mechanisms involve the interaction between unpaired electrons attached to different molecules. Under the influence of a magnetic field, the balance in this pair will change enough to affect the nature of chemical reactions, causing a cascade of biological effects determined by the orientation of the magnetic field.
• Magnetoreception based on magnetite mechanisms is a simpler way of sensing the magnetic field. It is believed that tiny crystals of iron-based compounds in the cells of living organisms respond to magnetic fields with a force strong enough to be detected. This enables animals to accurately determine their direction of movement.

Calculations by physicists have shown that inductive mechanisms do not approach the quantum level of sensitivity. However, radical-pair mechanisms may approach quantum limits, much like our technologies.

The findings of the study could not only assist in the development of new magnetometric devices but also enhance our understanding of the evolution of life on Earth that can sense magnetic fields.