TOLERANCES AND GAIN OF ASYMMETRIC JOSEPHSON JUNCTION INTERFEROMETER FOR AND GATES

B. T. Ulrich, T. Lee

Z. Hao, T. Shaw, Mehdi Hatefipour +5 more

Nearly quantum limited Josephson parametric amplifiers (JPAs) are essential components in superconducting quantum circuits. However, higher order nonlinearities of the Josephson cosine potential are known to cause gain compression, therefore limiting scalability. In an effort to reduce the fourth order, or Kerr nonlinearity, we realize a parametric amplifier with an Al-InAs superconductor–semiconductor hybrid Josephson junction (JJ). We extract the Kerr nonlinearity of the Al-InAs JJ from two different devices and show that it is three orders of magnitude lower compared to an Al-AlOX junction with identical Josephson inductance. We then demonstrate a four-wave-mixing (4WM) parametric amplifier made with an Al-InAs junction that achieves more than 20 dB of gain and −119 dBm of compression power, which outperforms single resonant JPAs based on Al junctions.

Sebastian Kempf

E. O. Schulz-DuBois, P. Wolf

Yu-Mei Gao, Xin-Ding Zhang, Lian Hu

We present a novel evolution method to obtain pure geometric phase with orthogonal superposed initial state method (OGSM). As examples we illustrate in detail the geometric evolution both in NMR and superconducting Josephson junction systems, which may be further designed to construct fault-tolerant geometric quantum gates. In the end we also propose a simple way to construct topological quantum gates based on OGSM.

Mikhail A. Galin, V. M. Krasnov, Alexander M. Klushin

We performed experimental investigations of the interaction between separate discrete niobium Josephson junction (JJ) arrays. It was found out that after tuning the arrays to the equal Josephson frequency the amplification of power is registered. The arrays are straight strip lines with 332 JJs oriented in parallel and located on common silicon substrate as well as on different substrates configured in a stack. The effect of amplification is observed at frequencies of up to 204 GHz while the gain relatively to the sum of power from alone radiated arrays can be as large as 3. These results indicate the mutual synchronization of niobium JJ arrays that would forces the submillimeter generation technique based on large JJ arrays with superwavelength dimensions.