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The phrase "quantum supremacy" sounds click-baity but it's actually bona-fide jargon. These guys are working with complexity theorists, such as Scott Aaronson a

The phrase "quantum supremacy" sounds click-baity but it's actually bona-fide jargon. These guys are working with complexity theorists, such as Scott Aaronson and Michael Bremner, to nail down specific tasks that are going to be completely impossible for classical computing. Part of the motivation is to move beyond the whole D-wave saga, and build something that for-sure kicks the shit out of current classical computing technology. Calling it "quantum supremacy" is a nice bit of marketing, imho. Earlier this year I sat down with the guy that runs the google quantum computing lab (Hartmut Neven) and chatted a bit about what they are building. One of the ideas is to be able to re-purpose silicon fab technology; whoever gets this to work (if it's possible) is going to win big. There are many other approaches being explored, by many research labs around the world. One particularly interesting idea is to use photonics (think fiber-optics), which has the great advantage of not needing to be ridiculously cold [1]. Source: me doing a PhD in the area. [1] https://arxiv.org/abs/1607.08535 https://arxiv.org/abs/1607.08535

philippnagel 10y ago
Could you elaborate on "repurpose silicon fab technology"? I know pretty much nothing about quantum computing. How does the manufacturing process differ?
- mathgenius 10y ago
  The attempts to build "qubits" involve very complicated custom gadgets, with strange crystals or superconductors, or other weird things I don't know much about. And then refrigerated down to almost absolute zero. And it's not just about mass producing qubits, they need to talk to each other, ie. be entangled. And that is the really hard part about all of this.
- ThePhysicist 10y ago
  Most superconducting qubits, such as the "Transmons" used by Google and various other labs are made of Aluminium, as this is a material which has good properties and can be easily deposited using e.g. evaporation-based methods (i.e. heat Aluminium in a vacuum so it evaporates and gets deposited on the surface of a chip that you put nearby). The microwave circuits on the chips are typically made out of Niobium (another superconductor), which is not very suited for making qubits but which provides very good properties for building large-scale structures such as coplanar waveguides. To fabricate a qubit, normally one first deposits Niobium on a Saphire/Silicon wafer and then etches structures into this using photo lithography. Afterwards, the Aluminium qubits get deposited using so-called shadow evaporation technique, where you create two layers of Aluminium separated by a thin insulating barrier that is created by first depositing a single layer of Aluminium, oxidizing it and then depositing another layer of Aluminium at a different angle. This process is quite finicky and the yield of working qubits you get out of it is (or at least was at the time I worked on this) rather low. Adapting techniques from conventional semiconductor manufacturing (were error rates are < 1^-9 per transistor) seems therefore very promising. So far it seems that there are still many hurdles to overcome for this, though the fabrication methods get more reliable every year.

philippnagel 10y ago

Could you elaborate on "repurpose silicon fab technology"? I know pretty much nothing about quantum computing. How does the manufacturing process differ?

mathgenius 10y ago
The attempts to build "qubits" involve very complicated custom gadgets, with strange crystals or superconductors, or other weird things I don't know much about. And then refrigerated down to almost absolute zero. And it's not just about mass producing qubits, they need to talk to each other, ie. be entangled. And that is the really hard part about all of this.
ThePhysicist 10y ago
Most superconducting qubits, such as the "Transmons" used by Google and various other labs are made of Aluminium, as this is a material which has good properties and can be easily deposited using e.g. evaporation-based methods (i.e. heat Aluminium in a vacuum so it evaporates and gets deposited on the surface of a chip that you put nearby). The microwave circuits on the chips are typically made out of Niobium (another superconductor), which is not very suited for making qubits but which provides very good properties for building large-scale structures such as coplanar waveguides. To fabricate a qubit, normally one first deposits Niobium on a Saphire/Silicon wafer and then etches structures into this using photo lithography. Afterwards, the Aluminium qubits get deposited using so-called shadow evaporation technique, where you create two layers of Aluminium separated by a thin insulating barrier that is created by first depositing a single layer of Aluminium, oxidizing it and then depositing another layer of Aluminium at a different angle. This process is quite finicky and the yield of working qubits you get out of it is (or at least was at the time I worked on this) rather low. Adapting techniques from conventional semiconductor manufacturing (were error rates are < 1^-9 per transistor) seems therefore very promising. So far it seems that there are still many hurdles to overcome for this, though the fabrication methods get more reliable every year.