基于菱形人工原子的超快QND测量
Ultrafast QND measurements based on diamond-shape artificial atom
摘要：
我们提出了一个量子非破坏（QND）读出方案的超导人工原子耦合到谐振腔中的电路QED架构，我们估计，没有Purcell效应的限制，一个非常高的测量保真度。该器件由两个通过大电感耦合的transmons组成，通过类交叉克尔项相互作用，产生一个菱形人工原子，一个逻辑量子比特和一个辅助量子比特。该辅助元件强耦合到传输线谐振器。根据量子比特状态，辅助物共振地或色散地耦合到谐振器，导致所传输的微波信号幅度的大对比度。这种原始的方法可以用最先进的约瑟夫森参量放大器来实现，从而在几十纳秒内实现QND测量，保真度高达99.9%。
英文摘要：
We propose a Quantum Non Demolition (QND) read-out scheme for a superconducting artificial atom coupled to a resonator in a circuit QED architecture, for which we estimate a very high measurement fidelity without Purcell effect limitations. The device consists of two transmons coupled by a large inductance, giving rise to a diamond-shape artificial atom with a logical qubit and an ancilla qubit interacting through a cross-Kerr like term. The ancilla is strongly coupled to a transmission line resonator. Depending on the qubit state, the ancilla is resonantly or dispersively coupled to the resonator, leading to a large contrast in the transmitted microwave signal amplitude. This original method can be implemented with state of the art Josephson parametric amplifier, leading to QND measurements in a few tens of nanoseconds with fidelity as large as 99.9 %.
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