Materials Characterization for Quantum Computation

该项目涉及测试用于量子计算和量子信息处理的最先进的超导设备。超导量子计算机的基石是约瑟夫森结。这是一个典型的亚微米尺度的隧道结，由**Nb/AlOx/Nb的三层光刻图案。对于量子计算和高性能SQUID传感器，这种超导器件必须具有非常稳定的量子隧穿电阻。材料方面已被发现是**负责这些设备的最终噪音限制。例如，在**氧化物屏障内或附近的缺陷会波动，导致隧道电阻中的低频噪声（1/f噪声）。同样，设备表面的磁性颗粒也会波动，导致设备看到的背景磁通量出现1/f噪声。对于量子计算的应用，这种噪声会导致退相干，这是量子信息的损失。这限制了量子比特的有效性。在SQUID磁力计的情况下，这**产生的残余磁噪声，限制了传感器的灵敏度。**提议的项目将与D-wave合作，D-wave是一家从事超导量子计算的公司，**建立一种可靠、有效的方法来表征基于约瑟夫森结的设备的质量，以**制造更高性能的量子计算机

This project involves testing state of the art superconducting devices used for quantum computing and quantum**information processing. The building block of the superconducting quantum computer is the Josephson**junction. This is typically a sub-micron scaled tunnel junction lithographically patterned from a trilayer of**Nb/AlOx/Nb. For quantum computing as well as high performance SQUID sensors, this superconducting**device must have a very stable quantum tunneling resistance. Materials aspects have been found to be**responsible for the ultimate noise limit for such devices. For example, defects within or in the vicinity of the**oxide barrier can fluctuate causing a low frequency noise (1/f noise) in the tunneling resistance. Similarly**magnetic particles on the surface of the device can fluctuate, causing 1/f noise in the background magnetic flux**seen by the device. For the application of quantum computing, this noise causes decoherence, which is a loss of**the quantum information. This limits the effectiveness of the qubit. In the case of SQUID magnetometers, this**produces a residual magnetic noise that limits the sensitivity of the sensor.**The proposed project will work with D-wave, a company working on superconducting quantum computation,**to set up a reliable, efficient way to characterize the quality of the Josephson junction based devices in order to**make higher performance quantum computers.**