Right now it is a pre-transistor in the 1920s and 1930s. Vacuum tubes are analogous to the computers that we have now. In 1925 a patent for the concept of a F

Right now it is a pre-transistor in the 1920s and 1930s. Vacuum tubes are analogous to the computers that we have now. In 1925 a patent for the concept of a FET was filed. It wasn't until 1948 that we had a working transistor. That took 23 years to go from concept to useful invention. It isn't too surprising that a quantum computer is harder.