Unwanted fluctuations in a magnetic field that can disrupt quantum states.Magnetic noise refers to the random, unwanted fluctuations in a magnetic field that can interfere with the delicate states of quantum systems. In quantum computing and sensing, qubits and other quantum states are extremely sensitive to their environment; a stray magnetic field variation can cause decoherence, destroying the quantum information being processed. This noise is a major obstacle to building reliable quantum technologies, as it can arise from a variety of sources, including thermal fluctuations in materials, electrical currents in nearby wires, or even external events like solar storms.
Magnetic noise originates from the motion of charges and the alignment of magnetic moments in materials. In a conductor, for example, thermal energy causes electrons to move randomly, creating fluctuating currents that generate a time-varying magnetic field. Similarly, in magnetic materials, the orientation of atomic spins can flip due to thermal agitation, producing a noisy magnetic environment. These fluctuations couple to quantum systems through the magnetic interaction, causing the energy levels of the quantum state to shift randomly, which leads to decoherence.
Understanding and mitigating magnetic noise is crucial for improving the coherence times of qubits in quantum computers and for enhancing the sensitivity of quantum sensors, such as magnetometers used in medical imaging and geological surveys.
Magnetic noise from solar storms can be so strong that it disrupts not only quantum experiments but also power grids on Earth.


