3 ms·

> They don't have a general purpose quantum computer, in particular, they can't run Shor's algorithm to factorize numbers and break a big part of encryption met

> They don't have a general purpose quantum computer, in particular, they can't run Shor's algorithm to factorize numbers and break a big part of encryption methods. What limitations does it have, other than not having enough qubits to run Shor's algorithm (Scott Aaronson mentions it would require thousands of logical qubits, translating to possibly millions of physical qubits due to error-correction requirements)? Scott's FAQ says: "The key difference with Google’s effort is that they have a fully programmable device—one that you can program with an arbitrary sequence of nearest-neighbor 2-qubit gates, just by sending the appropriate signals from your classical computer." Unfortunately, I don't know what "arbitrary sequence of nearest-neighbor 2-qubit gates" means and what kinds of algorithms are out of reach for that method.

krastanov 7y ago
> arbitrary sequence of nearest-neighbor 2-qubit gates The classical equivalent is (very handwavily) a processor that can perform all the ops from a reasonable small ISA, but each op has 1% chance of failing silently. Hence, any quantum algorithm can be put on this device in principle, but you are limited to stuff that uses only 50 qubits and does not mind the 1% error. There are not really any useful things you can do in the presence of (accumulating) 1% errors, beside proof of concept contrived problems.
- BurningFrog 7y ago
  ISA = Instruction Set Architecture https://en.wikipedia.org/wiki/Instruction_set_architecture https://en.wikipedia.org/wiki/Instruction_set_architecture
eternalban 7y ago
> What limitations does it have, other than not having enough qubits .. Would appreciate informed commentary on the scaling characteristic of the current approaches. It seems reasonable to question whether that the scaling challenge itself will prove to be as formidable as solving certain problems. Is it?

krastanov 7y ago

> arbitrary sequence of nearest-neighbor 2-qubit gates The classical equivalent is (very handwavily) a processor that can perform all the ops from a reasonable small ISA, but each op has 1% chance of failing silently. Hence, any quantum algorithm can be put on this device in principle, but you are limited to stuff that uses only 50 qubits and does not mind the 1% error. There are not really any useful things you can do in the presence of (accumulating) 1% errors, beside proof of concept contrived problems.

BurningFrog 7y ago
ISA = Instruction Set Architecture https://en.wikipedia.org/wiki/Instruction_set_architecture https://en.wikipedia.org/wiki/Instruction_set_architecture

eternalban 7y ago

> What limitations does it have, other than not having enough qubits .. Would appreciate informed commentary on the scaling characteristic of the current approaches. It seems reasonable to question whether that the scaling challenge itself will prove to be as formidable as solving certain problems. Is it?