The quantum mechanical systems used in quantum technologies, for example individual atoms, are very sensitive: any interaction with the environment can cause changes and thus lead to errors. However, this remarkable sensitivity of quantum mechanical systems to environmental factors can also be an advantage. Due to their sensitivity, quantum sensors can outperform conventional sensors in terms of precision, for example when measuring magnetic fields or gravity.
The comparison is certain
The sensitive quantum mechanical properties required for sensor technology can be masked by noise - caused by rapid interactions between the sensor and the environment, which disrupt the information in the sensor and make the quantum signal unreadable. In a new paper, physicists led by Christian Roos from the Institute of Experimental Physics at the University of Innsbruck, together with partners in Israel and the USA, present a method for making this information accessible again using "correlation spectroscopy". "The key idea here is that we don’t just use a single sensor, but a network of up to 91 sensors, each consisting of a single atom," explains Helene Hainzer, the first author of the paper. "Since the noise affects all sensors equally, by analyzing simultaneous changes in the states of all sensors, we can effectively remove the environmental noise and recover the information to be measured. This allows us to precisely measure variations in the magnetic field in the environment, as well as determine the distance between the quantum sensors." In addition, the method is applicable to various other sensing tasks and within different experimental platforms, reflecting its versatility.Precision increases with the number of sensors
Correlation spectroscopy has already been implemented in the past with two atomic clocks, resulting in unprecedented accuracy in time measurement. "Our work is the first application of this method for such a large number of atoms or sensors," emphasizes ERC award winner Christian Roos. "In fact, we have developed a completely new experimental setup over several years to enable experimental control over so many atoms." In their publication, the Innsbruck scientists show that the precision of the sensor measurements increases with the number of particles in the sensor network. Remarkably, entanglement - which is commonly used to increase the accuracy of quantum sensors but is difficult to generate in the laboratory - offers no advantage compared to the multi-sensor system now demonstrated.The work has been published in the journal Physical Review X and was financially supported by the Austrian Science Fund FWF, the Austrian Federal Ministry of Education, Science and Research, the European Union and the Federation of Austrian Industries Tyrol, among others.
Publication: Correlation spectroscopy with multiqubit-enhanced phase estimation. Phys. Rev. X. H. Hainzer, D. Kiesenhofer, T. Ollikainen, M. Bock, F. Kranzl, M. K. Joshi, G. Yoeli, R. Blatt, T. Gefen, and C. F. Roos. Phys. Rev. X 14, 011033 DOI: 10.1103/PhysRevX.14.011033
