Tan D, Weber S J, Siddiqi I, Mølmer K, Murch K W
Department of Physics, Washington University, St. Louis, Missouri 63130, USA.
Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA.
Phys Rev Lett. 2015 Mar 6;114(9):090403. doi: 10.1103/PhysRevLett.114.090403. Epub 2015 Mar 5.
The quantum state of a superconducting transmon qubit inside a three-dimensional cavity is monitored by transmission of a microwave field through the cavity. The information inferred from the measurement record is incorporated in a density matrix ρ_{t}, which is conditioned on probe results until t, and in an auxiliary matrix E_{t}, which is conditioned on probe results obtained after t. Here, we obtain these matrices from experimental data and we illustrate their application to predict and retrodict the outcome of weak and strong qubit measurements.
通过微波场在三维腔体内的传输来监测超导传输子量子比特在腔内的量子态。从测量记录中推断出的信息被纳入密度矩阵ρₜ，它以直到t时刻的探测结果为条件，以及辅助矩阵Eₜ，它以t时刻之后获得的探测结果为条件。在这里，我们从实验数据中获得这些矩阵，并说明它们在预测和回溯弱和强量子比特测量结果中的应用。
