Pashin Dmitrii, Bastrakova Marina, Satanin Arkady, Klenov Nikolay
Faculty of Physics, Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod, Russia.
Russian Quantum Center, 143025 Moscow, Russia.
Sensors (Basel). 2022 Aug 31;22(17):6580. doi: 10.3390/s22176580.
We study bifurcation behavior of a high-quality (high-Q) Josephson oscillator coupled to a superconducting qubit. It is shown that the probability of capture into the state of dynamic equilibrium is sensitive to qubit states. On this basis we present a new measurement method for the superposition state of a qubit due to its influence on transition probabilities between oscillator levels located in the energy region near the classical separatrix. The quantum-mechanical behavior of a bifurcation oscillator is also studied, which makes it possible to understand the mechanism of "entanglement" of oscillator and qubit states during the measurement process. The optimal parameters of the driving current and the state of the oscillator are found for performing one-qubit gates with the required precision, when the influence on the qubit from measurement back-action is minimal. A measurement protocol for state populations of the qubit entangled with the oscillator is presented.
我们研究了与超导量子比特耦合的高品质（高Q）约瑟夫森振荡器的分岔行为。结果表明，捕获到动态平衡状态的概率对量子比特状态敏感。在此基础上，由于其对位于经典分界线附近能量区域的振荡器能级之间跃迁概率的影响，我们提出了一种用于量子比特叠加态的新测量方法。还研究了分岔振荡器的量子力学行为，这使得理解测量过程中振荡器和量子比特状态的“纠缠”机制成为可能。当测量反作用对量子比特的影响最小时，找到了用于以所需精度执行单量子比特门的驱动电流的最佳参数和振荡器的状态。提出了一种用于与振荡器纠缠的量子比特状态布居的测量协议。
