Posted in | Quantum Physics

Precise Functioning of Quantum Sensors Induced by Chaotic Dynamics

It is already known that quantum sensors have the ability to accurately measure entities such as accelerations, magnetic field strength, or temperature. Moreover, they function with more precision with chaotic dynamics.

Physicists from the University of Tübingen have demonstrated this in a research in which they devised a technique that can enhance the measurement accuracy of high-precision sensors by a further 70%. Weak laser pulses in a computer simulation were used by doctoral candidate Lukas Fiderer and Professor Daniel Braun at the Institute of Theoretical Physics to perturb the dynamics of a magnetic field sensor. The outcomes of the research have been reported in the Nature Communications journal.

Quantum metrology is a field of metrology, or the science of measurement, which is different from traditional measuring techniques since quantum systems such as photons or atoms are used as sensors that can be explained only using the laws of quantum mechanics. Traditional sensors obey regular, predictable dynamics. They are developed such that chaos - a term used in theoretical physics to describe the dynamics in which disturbances grow exponentially - is prevented; else, the measurement of parameters would be unpredictable or even impossible. However, quantum sensors obey other laws: Quantum chaos is by no means related to unpredictability.

Therefore, the researchers analyzed the way measurement accuracy would get altered if the quantum sensor behaves in an increasingly chaotic manner and not in a regular way. They used formulas to explain a physical model and then developed a computer simulation of a quantum sensor, the atomic vapor magnetometer, and its dynamics. Atomic vapor magnetometers have already been known to be highly accurate magnetic field sensors containing a vapor of alkali atoms in a glass cell.

When the cell is located in a magnetic field, the atoms rotate similar to small compass needles. Researchers can measure the magnetic field by using a laser to measure the direction of rotation. “In the simulation, we fired weak laser pulses at the atoms during the measurement process to render the dynamics chaotic,” explained Lukas Fiderer, who initiated this study as part of his master thesis and is pursuing his doctorate at present.

The study showed an enhancement in measurement accuracy of 70%. An absolute benefit is the fact that the chaotic dynamics can be established such that the sensor is more rugged against perturbing interactions with the environment. The researchers have already filed for a patent for the innovative magnetic field sensor. “We hope that our model will soon be implemented experimentally and assume that the method will be used in various quantum sensors. It could pave the way forward to more accurate and robust sensors.”

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