In 1969, IBM Research at Yorktown Heights launched what would become the largest single R&D program in the company's history outside of System/360. The goal, championed by German-born physicist Wilhelm Anacker, was audacious: build a general-purpose computer using Josephson junctions — superconducting switches that flip states in picoseconds while dissipating almost no power. Cycle time target: 2 nanoseconds. Room-temperature silicon at the time struggled to hit 100.

The physics was gorgeous. Brian Josephson had predicted in 1962 (Nobel Prize 1973) that a superconducting current would tunnel across a thin insulating barrier without resistance, and that this junction could be switched between zero-voltage and finite-voltage states by a tiny magnetic field. Switch it fast enough and you had a logic gate that ran at 4 kelvin, dissipated microwatts instead of milliwatts, and — critically — could be packed into a dense 3D block because it produced almost no heat to remove.

IBM built it. By 1980 the team had demonstrated working 4-bit ALUs, a 4 Kbit cache memory chip, and multi-gigahertz shift registers using lead-alloy tunnel junctions. Anacker's Scientific American article in January 1979 laid out a machine with 2 ns cycle time in a package the size of a coffee cup. At peak the program employed over 100 researchers and consumed roughly $250-300 million across 14 years.

Then, on September 23, 1983, IBM cancelled it. The reasons were mundane:

• Materials failure. Lead-alloy junctions cracked from thermal cycling between 300 K and 4 K. IBM switched to niobium, but the process wasn't ready.
• Silicon caught up. CMOS was hitting scaling milestones nobody at Yorktown had modeled. By 1983, a hot ECL bipolar chip could do what Anacker promised, at room temperature.
• The cryostat problem. Liquid helium plumbing terrified IBM's mainframe customers, who wanted machines that fit in a data center — not a physics lab.
• No killer app. A 2 ns cycle was cool. Was it $50,000-per-hour-of-helium cool? Sales couldn't answer.

Anacker's team dispersed. Some went to Japan's MITI, which ran its own superconducting computer program until the mid-1990s. Others founded HYPRES in 1983, still selling superconducting electronics today.

Why revisit it now? Because we built it anyway — just for a different job.

Every superconducting quantum computer in operation — IBM Quantum's own Condor, Google's Willow, Rigetti's Ankaa, IQM's chips — is a lattice of Josephson junctions operating at 15 millikelvin. IBM's abandoned junction fabrication process is the direct ancestor of the qubits IBM Research now sells cloud access to. The company killed the technology, kept the lab, and stumbled back into it 30 years later through a different door.

Meanwhile, classical superconducting logic never died. Rapid Single Flux Quantum (RSFQ) circuits, invented in Moscow in 1985, run at 770 GHz with picowatt-per-gate power. IARPA's C3 program (2014-2019) funded a serious attempt to build a superconducting exascale supercomputer — and concluded it was feasible. Northrop Grumman, MIT Lincoln Lab, and Seeqc are all shipping AQFP and ERSFQ chips today.

Modern EUV lithography lets us pack 10⁸ junctions per cm² versus Anacker's 10⁴. Closed-cycle cryocoolers (no plumbing) fit in a rack. And the datacenter thermal budget that killed Anacker's coffee-cup dream is now the single largest constraint on AI training. A 4 K logic core dissipating 1/1000th the power of a GPU, paired with the cryostat already required for its quantum accelerator, is no longer absurd.