Bath-engineering technique for criticality-based quantum metrology with amplitude noise.

Quantum critical systems are extremely sensitive to parameter variation near the critical point. Moreover, the derivatives with respect to the order parameter may exhibit divergence. This quantum criticality is widely utilized to enhance the performance of quantum metrology.

Observing quantum coherent oscillations in a three-level atom via electromagnetically induced transparency by two-dimensional spectroscopy.

Two-dimensional electronic spectroscopy (2DES) has high spectral resolution and is a useful tool for studying atomic dynamics. In this paper, we show a smallest unit of electromagnetically induced transparency (EIT) for 2DES, i.e.