Efficient Direct Measurement of Arbitrary Quantum Systems via Weak Measurement
Changliang Ren, Ya Wang, Jiangfeng Du · Physical Review Applied · 2019
Efficient, reliable determination of a system's state is at the heart of quantum science. Directly measuring any desired density-matrix elements is a unique challenge for both theorists and experimentalists, as standard methods have always suffered from the rapid increase in complexity of measurements and reconstruction algorithms. This study presents an efficient scheme for directly measuring arbitrary density matrices with only one strong measurement, or a weak measurement, of each qudit. This method is important for characterizing large-scale quantum systems, and the technology that will be derived from it will be easy to expand and integrate, for example, on a quantum chip.