Already, the graphene efforts have offered “a breath of fresh air” to the community, Alicea says. “It’s one of the most promising avenues that I’ve seen in a while.” Since leaving Microsoft, Zaletel has shifted his focus to graphene. “It’s clear that this is just where you should do it now,” he says.
But not everyone believes they will have enough control over the free-moving quasiparticles in the graphene system to scale up to an array of qubits—or that they can create big enough gaps to keep out intruders. Manipulating the quarter-charge quasiparticles in graphene is much more complicated than moving the Majoranas at the ends of nanowires, Kouwenhoven says. “It’s super interesting for physics, but for a quantum computer I don’t see it.”
Just across the parking lot from Station Q’s new office, a third kind of Majorana hunt is underway. In an unassuming black building branded Google AI Quantum, past the company rock-climbing wall and surfboard rack, a dozen or so proto–quantum computers dangle from workstations, hidden inside their chandelier-like cooling systems. Their chips contain arrays of dozens of qubits based on a more conventional technology: tiny loops of superconducting wires through which current oscillates between two electrical states. These qubits, like other standard approaches, are beset with errors, but Google researchers are hoping they can marry the Majorana’s innate error protection to their quantum chip.
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