ABSTRACT
Quantum sensing with continuous monitoring represents a significant research direction in quantum technologies, particularly promising in the acoustic frequency regime. This potential offers a wide range of scientific applications, including the measurement of weak forces-such as gravitational wave signals emitted by extreme astronomical events -and the detection of magnetic fields generated by brain’s activity, heart beat.
Two fundamental challenges in enhancing the sensitivity of current gravitational wave detectors are managing two competing types of quantum noise; shot noise: which arises from the uncertainty associated with the arrival of photons, and quantum backaction noise: which results from the transfer of photon momentum to the probe sensor as radiation pressure during the interaction. Both types of noise arise from the quantum nature of light, scale differently with the light power, and dominate at different frequencies. Their broadband reduction requires the injection of a squeezed vacuum source, with frequency-dependent rotation of the squeezed quadrature accomplished via a 300 m long detuned filter cavity.
In this talk, I will present a potential alternative approach in which these two competing types of quantum noise can be reduced simultaneously using a hot atomic ensemble empowered by an EPR-entangled source. In the first part, I will introduce the concept of collective spin oscillators with effective masses and present the experimental implementation of a quantum spin oscillator operating in the acoustic regime. In the second part, I will describe a hybrid quantum system involving the spin oscillator and a non-degenerate EPR entangled source and present the similar frequency dependent squeezing (FDS) source achieved by our hybrid quantum network. Finally, if time permits, I will briefly discuss the potential application of such FDS source beyond gravitational wave detector, such as in optical pumped atomic magnetometers.
BIOGRAPHY
Dr. Jun Jia is a research associate at Quantop, Niels Bohr Institute, University of Copenhagen. He received his PhD from the University of Copenhagen in 2024 under the supervision of Eugene S. Polzik. He then continued as a postdoc, where he worked on an experiment for potential overcoming the standard quantum limit in gravitational wave detectors using parallel effective negative-mass spin oscillators. Before that, he obtained his master’s degree at East China Normal university.
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